Kinetic frictional plastics sorter and kinetic frictional separating plastic species

Abstract

A kinetic frictional plastics sorter (200) includes a sorting platform (201) disposed on a support base (203), a heater (202) in thermal communication with the sorting platform, and a vibrator (211) in mechanical communication with the sorting platform. The sorting platform is heated by the heater to a first temperature to spatially separate different plastics in the mixed plastics composition (210). The vibrator produces vibrations that are communicated to the sorting platform to vibrate the sorting platform. The vibrations cause the plastics in the mixed plastics composition to slide down the sorting platform at different velocities that depend on the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition. The velocity of a first plastic is greater than the velocity of a second plastic at the first temperature so that the first plastic is spatially separated from the second plastic on the sorting platform.

Description

KINETIC FRICTIONAL PLASTICS SORTER AND KINETIC FRICTIONALSEPARATING PLASTIC SPECIESSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0001] This invention was made with United States Government support from the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce. The Government has certain rights in this invention.CROSS-REFERENCE TO RELATED APPLICATION

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 610,479 (filed December 15, 2023), which is herein incorporated by reference in its entirety.BRIEF DESCRIPTION

[0003] Disclosed is a kinetic frictional plastics sorter for kinetic frictional separating plastic species in a mixed plastics composition, the sorter comprising: a sorting platform disposed on a support base and in thermal communication with a heater, the sorting platform being arranged at an inclination angle with respect to the support base, the sorting platform being heated by the heater to a first temperature sufficient to spatially separate different plastics in the mixed plastics composition, the sorting platform receiving the mixed plastics composition, such that plastics in the mixed plastics composition slide down the sorting platform under the action of gravity at different velocities that depend on the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition, and the velocity of a first plastic is greater than the velocity of a second plastic at the first temperature so that the first plastic is spatially separated from the second plastic on the sorting platform; a heater in thermal communication with the sorting platform and that heats the mixed plastics composition disposed on the sorting platform to the first temperature to provide spatial separation of the different plastics in the mixedplastics composition due to the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; and a mixed plastics composition comprising a first plastic and a second plastic, such that the first plastic has a smaller coefficient of kinetic friction than the second plastic and moves at a greater velocity down the sorting platform and travels a greater distance down the sorting platform than the second plastic whose melting point is greater than the first temperature of the sorting platform.

[0004] Disclosed is a process for sorting plastics, comprising: providing a mixed plastics composition comprising a first plastic and a second plastic, wherein the first plastic has a smaller coefficient of kinetic friction than the second plastic; heating the mixed plastics composition to a first temperature sufficient to spatially separate different plastics in the mixed plastics composition due to the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; disposing the mixed plastics composition on a sorting platform arranged at an inclination angle with respect to a support base; allowing the plastics in the mixed plastics composition to slide down the sorting platform under the action of gravity at different velocities that depend on the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; collecting the first plastic in a first collector at a first time; and separately collecting the second plastic in a second collector at a second time that is subsequent to the first time, wherein the first time and the second time for separately collecting the first plastic and the second plastic is based on their respective velocities.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The following description cannot be considered limiting in any way. Various objectives, features, and advantages of the disclosed subject matter can be more fully appreciated with reference to the following detailed description of the disclosed subject matter when considered in connection with the following drawings, in which like reference numerals identify like elements.

[0006] FIG. 1 shows, according to some embodiments, a kinetic frictional plastics sorter 200 and steps involved in kinetic frictional separating plastic species in a mixed plastics composition.

[0007] FIG. 2 shows, according to some embodiments, the kinetic frictional plastics sorter and more steps involved in kinetic frictional separating plastic species in a mixed plastics composition.

[0008] FIG. 3 shows, according to some embodiments, the kinetic frictional plastics sorter and more steps involved in kinetic frictional separating plastic species in a mixed plastics composition.

[0009] FIG. 4 shows, according to some embodiments, the kinetic frictional plastics sorter and more steps involved in kinetic frictional separating plastic species in a mixed plastics composition.

[0010] FIG. 5 shows, according to some embodiments, steps involved in kinetic frictional separating plastic species in a mixed plastics composition.

[0011] FIG. 6 shows, according to some embodiments, a graph of coefficient of friction for various plastics and several of the various plastics.

[0012] FIG. 7 shows, according to some embodiments, show a computing system for controlling aspects of kinetic frictional separating plastic species, acquisition of data, and analysis of data for a kinetic frictional plastics sorter.

[0013] FIG. 8 shows (A) the frictional force FF, (B) change in gap height, and (C) normal force FN during a temperature ramp for LDPE. Data is stable until approximately ? = 115 °C. Conditions: vs = 5 mm / s, P = 15 kPa.

[0014] FIG. 9 shows (A) coefficient of kinetic friction, (B) Differential scanning calorimetry (DSC), and (C) tensile moduli of LDPE during a temperature ramp. Conditions: vs = 5 mm / s, P = 15 kPa.

[0015] FIG. 10 shows (A) coefficient of kinetic friction, (B) thermal data, and (C) tensile moduli of iPP during a temperature ramp. Conditions: vs = 5 mm / s, P = 15 kPa.

[0016] FIG. 11 shows (A) coefficient of kinetic friction, (B) DSC data, and (C) tensile moduli of HDPE during a temperature ramp. Conditions: vs = 5 mm / s, P = 15 kPa.

[0017] FIG. 12 shows coefficient of kinetic friction for HDPE for (A) a range of sliding velocities at a constant pressure of P = 15 kPa and (B) a range of pressures at constant sliding velocity vs = 5 mm / s.

[0018] FIG. 13 shows (A) coefficient of kinetic friction, (B) thermal data, and (C) tensile moduli of PET during a temperature ramp. Conditions: vs = 5 mm / s, P = 15 kPa.

[0019] FIG. 14 shows CoF (A) and modulus (B) results for four plastics.DETAILED DESCRIPTION

[0020] A detailed description of one or more embodiments is presented herein by way of exemplification and not limitation.

[0021] Recycling of plastic waste has the benefits of reducing plastic pollution, keeping valuable materials within the working economy, and reducing greenhouse gas emissions. A conventional method for plastic recycling is mechanical recycling. To maximize performance of recyclates made by mechanical recycling, the plastic waste is often first sorted by type. For example, recycled polyethylene performs best when it is sorted from other plastics such as polypropylene. If not, the result can be can recyclates in materials with reduced properties, such as brittleness. When mixed plastics are present in the recyclates, the economic value of the material, and hence the recycling rates are reduced.

[0022] Conventional plastics sorting systems can include a combination of optical and mechanical sorting techniques to separate different types of plastics. Optical sorting systems use cameras and sensors to detect the color and / or shape of plastics, while mechanical sorting systems use air jets or other physical forces to separate plastics based on their size, shape, or density. While conventional plastics sorting systems are effective in sorting some types of plastics, they have several limitations. Optical sorting systems can be expensive to operate and maintain, and they can be difficult to use for sorting plastics that are similar in color or shape. Mechanical sorting systems can be noisy and produce a lot of waste, and they can be difficult to use for sorting plastics that are of different sizes or shapes.

[0023] Conventional sortation of plastics can include manual sortation (e.g., by hand), screening, material sorting, size reduction, extrusion, and pelletization. Within material sorting, processes can include devices or steps such as an air classifier, ballistic sorter, sink-float sorterjigging, hydrocloning, electrostatic sortation, magnetic density sortation, flotation, sensor-based sortation, hyperspectral imaging, x-ray fluorescence, and others. Although there are conventional sortation methods, conventional sortation for the most part fails to provide purity over 95%. Postconsumer waste can contain polyethylene and polypropylene, which are difficult to separate from each due to similarities in their densities and spectral features.

[0024] The kinetic frictional plastics sorter 200 overcomes the limitations of conventional plastics sorting systems by using a novel sorting technique that is based on the kinetic coefficients of friction between different types of plastics. The kinetic frictional plastics sorter 200 sorts plastics of different types, colors, sizes, and shapes with high accuracy and efficiency. Kinetic frictional plastics sorter 200 is also relatively inexpensive to operate and maintain, and it produces very little waste. The kinetic frictional plastics sorter 200 is a significant improvement over conventional plastics sorting systems. Kinetic frictional plastics sorter 200 is more accurate, efficient, and cost-effective than conventional systems. Kinetic frictional plastics sorter 200 is also more environmentally friendly, as it produces less waste.

[0025] Kinetic frictional plastics sorter 200 kinetic frictional separates plastic species in a mixed plastics composition 210. In an embodiment, with reference to FIG. 1 , FIG. 2, FIG. 3, FIG. 4, and FIG. 5, kinetic frictional plastics sorter 200 for kinetic frictional separating plastic species includes: a sorting platform (201 ) disposed on a support base (203) and in thermal communication with a heater (202) and in mechanical communication with the support base (203) and that is arranged at an inclination angle (204) with respect to the support base (203), is heated by the heater (202) to a first temperature sufficient to spatially separate different plastics in the mixed plastics composition (210), receives the mixed plastics composition (210), such that plastics in the mixed plastics composition (210) slide down the sorting platform (201 ) under the action of gravity at different velocities that depend on the kinetic coefficients of friction between the sorting platform (201 ) and each different type of plastic (206) in the mixed plastics composition (210), and the velocity of a first plastic (206.1 ) is greaterthan the velocity of the second plastic (206.2) at the first temperature so that the first plastic (206.1 ) is spatially separated from the second plastic (206.2) on the sorting platform (201 ); heater (202) in thermal communication with the sorting platform (201 ) and that heats the mixed plastics composition (210) disposed on the sorting platform (201 ) to the first temperature to provide spatial separation of the different plastics in the mixed plastics composition (210) due to the kinetic coefficients of friction between the sorting platform (201 ) and each different type of plastic (206) in the mixed plastics composition (210); and optionally a mixed plastics composition (210) that comprises a first plastic (206.1 ) and a second plastic (206.2), such that the first plastic (206.1 ) has a smaller coefficient of kinetic friction than the second plastic (206.2) and moves at a greater velocity down the sorting platform (201 ) and travels a greater distance down the sorting platform (201 ) than the second plastic (206.2) whose melting point is greater than the first temperature of the sorting platform (201 ).

[0026] In an embodiment, kinetic frictional plastics sorter 200 includes support base 203 on which is disposed sorting platform 201 and in mechanical communication with sorting platform 201 and that receives sorting platform 201 and provides a mechanically supportive base so that sorting platform 201 can be inclined at inclination angle 204 with respect to support base 203.

[0027] In an embodiment, kinetic frictional plastics sorter 200 includes collector 205 in communication with sorting platform 201 and that receives separated species of plastic 206 from mixed plastics composition 210 that are kinetic frictionally separated on sorting platform 201 , such that a first collector 205.1 collects a first plastic 206.1 and a second collector 205.2 collects a second plastic 206.2.

[0028] In an embodiment, kinetic frictional plastics sorter 200 includes vibrator 211 in mechanical communication with sorting platform 201 and that produces vibrations that are mechanically communicated to sorting platform 201 , such that sorting platform 201 is subjected to the vibrations.

[0029] Kinetic frictional plastics sorter 200 can be made of various elements and components that can be assembled together or fabricated. Elements of kinetic frictional plastics sorter 200 can be various sizes and shapes. Elements of kinetic frictional plastics sorter 200 can be made of a material that is physically or chemicallyresilient in an environment in which kinetic frictional plastics sorter 200 is disposed. Exemplary materials include a metal, ceramic, thermoplastic, glass, semiconductor, and the like. The elements of kinetic frictional plastics sorter 200 can be made of the same or different material and can be monolithic in a single physical body or can be separate members that are physically joined.

[0030] The kinetic frictional plastics sorter 200 is a device for separating different types of plastic from a mixed plastic composition. The sorter includes sorting platform 201 , heater 202, and vibrator 211 . Sorting platform 201 is disposed on support base 203 and is arranged at inclination angle 204 with respect to support base 203. Sorting platform 201 is heated by heater 202 to a first temperature sufficient to spatially separate different plastics in the mixed plastic composition 210. The mixed plastic composition 210 is received on sorting platform 201 , such that plastics in the mixed plastic composition 210 slide down sorting platform 201 under the action of gravity at different velocities that depend on the kinetic coefficients of friction between sorting platform 201 and each different type of plastic 206 in the mixed plastic composition 210. The velocity of a first plastic 206.1 is greater than the velocity of the second plastic 206.2 at the first temperature so that the first plastic 206.1 is spatially separated from the second plastic 206.2 on sorting platform 201 .

[0031] Vibrator 211 can be in mechanical communication with sorting platform 201 and produces vibrations that are mechanically communicated to sorting platform 201 , such that sorting platform 201 is subjected to the vibrations. The vibrations cause the plastics in the mixed plastic composition 210 to more efficiently slide down sorting platform 201 at their different velocities. This further enhances the spatial separation of the different plastics in the mixed plastic composition 210.

[0032] Sorting platform 201 can be a flat, rigid surface that is disposed on support base 203 and in thermal communication with heater 202. Sorting platform 201 is arranged at inclination angle 204 with respect to support base 203. Sorting platform 201 is heated by heater 202 to a first temperature sufficient to spatially separate different plastics in mixed plastics composition 210. Sorting platform 201 receives mixed plastics composition 210, such that plastics in mixed plastics composition 210 slide down sorting platform 201 under the action of gravity at different velocities that depend on the kinetic coefficients of friction between sorting platform 201 and eachdifferent type of plastic 206 in mixed plastics composition 210. The velocity of a first plastic 206.1 is greater than the velocity of the second plastic 206.2 at the first temperature so that the first plastic 206.1 is spatially separated from the second plastic 206.2 on sorting platform 201 . Sorting platform 201 can have a surface in contact with mixed plastics composition 210, wherein the surface can be metal, ceramic, composite, thermoset or a thermoplastic plastic with a higher melting point than the plastics 206 in mixed plastics composition 210 to be sorted. Sorting platform 201 can be made of a material that has a coefficient of friction with plastics, such as Teflon or PTFE. Sorting platform 201 can have an arbitrary surface roughness and can be a uniform surface or heterogeneous surface, which helps to ensure that the plastics slide evenly down the surface. Sorting platform 201 can be sloped at a selected inclination angle 204, to set the velocity of the plastics as they slide down the surface. This separates the plastics based on their kinetic coefficients of friction. Sorting platform 201 can be vibrated by vibrator 211. The vibrations help to loosen the plastics on sorting platform 201 and to prevent them from sticking to the surface. The vibrations can redistribute or mix the plastics on sorting platform 201 , which further helps to ensure that the plastics are separated evenly.

[0033] Sorting platform 201 can be stationary or have dynamic motion such as involved with a conveyor belt.

[0034] Heater 202 is a device that heats sorting platform 201 or plastics 206 in mixed plastics composition 210 disposed on sorting platform 201 to a first temperature sufficient to spatially separate different plastics in mixed plastics composition 210. Heater 202 can be any type of heater that is capable of heating sorting platform 201 to the desired temperature. Some examples of heaters that can be used include electric heaters, gas heaters, and infrared heaters. Heater 202 can be in thermal communication with sorting platform 201 either in direct contact with sorting platform 201 or indirectly wherein there can be a heat transfer medium (e.g., a thermal transfer material, air, and the like) between heater 202 and sorting platform 201. This allows heater 202 to transfer heat to sorting platform 201 more efficiently. Heater 202 can be in mechanical communication with sorting platform 201 so that heater 202 is attached to sorting platform 201 , or heater 202 is movable relative to sorting platform 201 . This allows heater 202 to be positioned in the desired locationon sorting platform 201 . Heater 202 can be arranged at inclination angle 204 with respect to support base 203. This angle allows heater 202 to heat sorting platform 201 more evenly. Heater 202 can be adjustable to allow the user to control the temperature of sorting platform 201. This allows the user to select the desired temperature for sorting platform 201 , depending on the type of plastics being sorted. Heater 202 can be durable and reliable. This allows heater 202 to withstand the rigors of industrial use. Heater 202 can be easy to use and maintain. This allows the user to operate and maintain heater 202 without difficulty. Heater 202 can be cost-effective. This allows the user to purchase and use heater 202 without incurring significant costs.

[0035] Support base 203 can be a rigid, flat surface that supports sorting platform 201 . Support base 203 can be made of a material such as metal or plastic that is resistant to heat and wear. Support base 203 can be arbitrary in shape (e.g., rectangular). It can have a raised edge around the perimeter to prevent sorting platform 201 from sliding off. Support base 203 can be mounted on a frame or stand that allows it to be tilted at an angle. This angle can be adjusted to vary the speed at which the plastics slide down sorting platform 201 . Support base 203 can be equipped with vibrator 211 that produces vibrations that are mechanically communicated to sorting platform 201 . These vibrations help to loosen the plastics and prevent them from sticking to sorting platform 201 or initiate sliding of plastic 206 on sorting platform 201. Support base 203 a stable surface for sorting platform 201 and helps to ensure that the plastics are sorted efficiently.

[0036] Inclination angle 204 is the angle between sorting platform 201 and support base 203. Inclination angle 204 can be an arbitrary angle, e.g., from 10 and 45 degrees, that is sufficient to cause the plastics in mixed plastics composition 210 to slide down sorting platform 201 under the action of gravity. Inclination angle 204 can be adjusted to optimize the separation of the different plastics in mixed plastics composition 210. Inclination angle 204 has several properties that affect the performance of the kinetic frictional plastics sorter 200. Inclination angle 204 affects the velocity of the plastics as they slide down sorting platform 201. The higher inclination angle 204, the greater the velocity of the plastics. Inclination angle 204 also affects the distance that the plastics travel down sorting platform 201. The higher inclination angle 204, the greater the distance that the plastics travel, depending onthe temperate of plastic 206 in mixed plastics composition 210 and their kinetic coefficients of friction on sorting platform 201 . Inclination angle 204 can affect the separation of the different plastics in mixed plastics composition 210. The plastics 206 with the higher coefficients of kinetic friction will travel at a slower velocity than the plastics with the lower coefficients of kinetic friction. This will cause the plastics to separate as they slide down sorting platform 201 . Inclination angle 204 is a parameter in the design of the kinetic frictional plastics sorter 200. Inclination angle 204 can be selected to optimize the separation of the different plastics 206 in mixed plastics composition 210.

[0037] Separating direction 209 is the direction in which the different plastics in mixed plastics composition 210 are separated. Separating direction 209 can be an acute angle with respect to the horizontal or substantially planar floor of a room. Separating direction 209 can be varied by adjusting curvature of sorting platform 201. Separating direction 209 can influenced or varied by adjusting the vibrations produced by vibrator 211.

[0038] Collector 205 is a device that collects the sorted plastics 206 from sorting platform 201 . Collector 205 can be made of a material that is compatible with the plastics that are being sorted, such as stainless steel or plastic. Collector 205 can be in the form of a chute, tray, container, or another sorting platform 201 or conveyor belt, and collector 205 can be located at the bottom of sorting platform 201 . Collector 205 can be sloped so that the sorted plastics will flow into collector 205. Collector 205 can have a screen or a filter to prevent small pieces of plastic from being lost. Collector 205 is responsible for collecting the sorted plastics and can be designed to be compatible with the plastics that are being sorted.

[0039] Vibrator 211 is a device that produces vibrations. It can include, e.g., a motor, weight, spring, and the like. The motor rotates the weight, which causes the spring or mass to stretch and contract. This movement creates vibrations that are transmitted to sorting platform 201. Vibrator 211 can be used to change the performance of the kinetic frictional plastics sorter 200 in several ways. The vibrations can loosen the plastics on sorting platform 201 , making it easier to initiate motion of the plastics on sorting platform 201 and for them to slide down. The vibrations can prevent the plastics from sticking to sorting platform 201. The vibrations can evenlydistribute the plastics on sorting platform 201 . Vibrator 211 can be operated in several different ways. The frequency and amplitude of the vibrations can be adjusted to suit the specific needs of the application. Vibrator 211 can also be operated in a continuous or pulsed mode. Vibrator 211 can be made of metal or plastic. It can be small and lightweight, making it easy to transport and install. Vibrator 211 can be powered by electricity, but it can also be powered by air, hydraulics, or potential energy.

[0040] Vibrational direction 207 is the direction in which sorting platform 201 vibrates. Vibrational direction 207 can be perpendicular to the surface of sorting platform 201 or in the plane of the exposed surface of sorting platform 201 that contacts plastics 206 in mixed plastics composition 210. Vibrational direction 207 can be varied to change the performance of the kinetic frictional plastics sorter 200. Vibrational direction 207 can be varied to increase the separation distance between different plastics in mixed plastics composition 210. Vibrational direction 207 can also be varied to change the efficiency of the kinetic frictional plastics sorter 200. Vibrational direction 207 can be varied to reduce the amount of time required to separate the different plastics in mixed plastics composition 210. Vibrational direction 207 can be varied by adjusting the position of vibrator 211. Vibrator 211 can be mounted on sorting platform 201 in a variety of positions. The position of vibrator 211 can affect vibrational direction 207. Vibrational direction 207 can also be varied by adjusting the frequency of the vibrations. The frequency of the vibrations can be adjusted by adjusting the power supply to vibrator 211 . The frequency of the vibrations can affect the separation distance between different plastics in mixed plastics composition 210. The frequency of the vibrations can affect the efficiency of the kinetic frictional plastics sorter 200.

[0041] Vibrational frequency 208 of vibrator 211 is a measure of how often sorting platform 201 vibrates. Vibrational frequency 208 can be adjusted to control the velocity at a given temperature at which the plastics in mixed plastics composition 210 slide down sorting platform 201 . It is contemplated that a higher vibrational frequency can cause the plastics to slide down sorting platform 201 more quickly, while a lower vibrational frequency can cause the plastics to slide down sorting platform 201 more slowly. Vibrational frequency 208 can also be used to control the spatial separationof the different plastics in mixed plastics composition 210. Vibrational frequency 208 can ensure that the plastics in mixed plastics composition 210 are not damaged. Vibrational frequency 208 can be selected based on the type of plastics being sorted and the desired spatial separation of the different plastics. Vibrational frequency 208 can also be adjusted to account for the different properties of the plastics, such as their density and coefficient of friction.

[0042] Mixed plastics composition 210 is a mixture of two or more different types of plastic 206. The plastics can be any type of plastic, including but not limited to polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyethylene terephthalate, and the like. The plastics can be in arbitrary form, including but not limited to pellets, granules, flakes, and powder and parts made from plastic. The plastics can be mixed in any proportions. Mixed plastics composition 210 has several properties that make it suitable for use in the kinetic frictional plastics sorter 200. The plastics in the composition have different coefficients of kinetic friction, which causes them to slide down sorting platform 201 at different velocities. The plastics also have different melting points, which causes them to melt at different temperatures. The vibrations produced by vibrator 211 help to break up the clumps of plastic and to prevent the plastics from sticking to sorting platform 201. The number of different plastics in mixed plastics composition 210 is arbitrary. In an embodiment, mixed plastics composition 210 includes a plurality of plastics 206. In an embodiment, mixed plastics composition 210 includes two different plastics 206, specifically a first plastic 206.1 and a second plastic 206.2. In an embodiment, mixed plastics composition 210 includes n-number of different plastics 206, specifically first plastic 206.1 , second plastic 206.2, ... , n-th plastic 206. n, wherein n is an arbitrary integer.

[0043] Plastic 206 can include a polymer that can be molded into a variety of shapes and forms, and it can be used in a wide range of applications, including packaging, construction, and consumer goods. Plastic 206 has a temperaturevariable kinetic coefficient of friction, which means that it slides over other surfaces at a velocity that relates to the temperature of the surface. This property allows the different plastics to be separated from each other. Plastic 206 can have a variety of colors and finishes and can be a recyclable material. Plastic 206 can include numerous types of plastics such as polyethylene terephthalate, high densitypolyethylene, low-density polyethylene, polypropylene, and the like that can be present in mixed form in a recycling stream. Plastics 206 from mixed plastics composition 210 are sorted by kinetic frictional plastics sorter 200 based on the temperature dependence of their coefficients of friction with respect to sorting platform 201 that can have a surface in contact with mixed plastics composition 210, wherein the surface can be metal, ceramic, composite, thermoset or a thermoplastic plastic with a higher melting point than the plastics 206 in mixed plastics composition 210 to be sorted.

[0044] With regard to plastic 206, it should be appreciated that the kinetic coefficient of friction becomes large (greater than 1 ) when the plastic is below, but within 10 °C, of the melting point of semi-crystalline plastics, such as polyethylene and polypropylene. The kinetic coefficient of friction also becomes large in thermoplastics when the plastic is above the melting point and the crystallinity is low, e.g., less than 20% by mass. Each type of plastic 206 has a distinct temperature at which the coefficient of friction becomes large, and this distinct temperature behavior is the basis for the separation of plastics 206 in mixed plastics composition 210.

[0045] It is contemplated that the surface of the plastics to be sorted can be clean of oil, food, or grime that would otherwise alter the coefficient of friction between surface and plastic. Plastic 206, which can be in the form of flakes, can be disposed on heated surface of sorting platform 201 that is inclined at inclination angle 204 with respect to the horizontal at an angle that causes plastic 206 to slide due to gravity or optionally vibration. Optionally, sorting platform 201 can be vibrated in addition to being heated and tilted.

[0046] Kinetic frictional plastics sorter 200 can be made in various ways. It should be appreciated that kinetic frictional plastics sorter 200 can include a number of optical, electrical, or mechanical components, wherein such components can be interconnected and placed in communication (e.g., optical communication, electrical communication, mechanical communication, fluid communication, and the like) by physical, chemical, optical, or free-space interconnects. The components can be disposed on mounts that can be disposed on a bulkhead for alignment or physical compartmentalization. As a result, kinetic frictional plastics sorter 200 can be disposed in a terrestrial environment or space environment. Elements of kinetic frictionalplastics sorter 200 can be formed from silicon, silicon nitride, and the like although other suitable materials, such as ceramic, glass, or metal can be used. According to an embodiment, the elements of kinetic frictional plastics sorter 200 are formed using 3D printing although the elements of kinetic frictional plastics sorter 200 can be formed using other methods, such as injection molding or machining a stock material such as block of material that is subjected to removal of material such as by cutting, laser oblation, and the like. Accordingly, kinetic frictional plastics sorter 200 can be made by additive or subtractive manufacturing. The various layers thus formed can be subjected to joining by bonding to form kinetic frictional plastics sorter 200.

[0047] The kinetic frictional plastics sorter 200 of feature 4 can be made and assembled by the following process. Support base 203 is fabricated from a suitable material, such as metal or plastic. Sorting platform 201 is fabricated from a suitable material, such as metal or plastic. Sorting platform 201 is attached to support base 203 in a suitable manner, such as by welding, bolting, or adhesive bonding. Heater 202 is attached to sorting platform 201 in a suitable manner, such as by welding, bolting, or adhesive bonding. Vibrator 211 is attached to sorting platform 201 in a suitable manner, such as by welding, bolting, or adhesive bonding.

[0048] Support base 203 can be fabricated from a material that has a high strength-to-weight ratio, such as aluminum, steel, or titanium. Sorting platform 201 is fabricated from a material that has a selected coefficient of friction with the plastics to be sorted, such as Teflon or PTFE. Heater 202 heats sorting platform 201 to a temperature that is sufficient to spatially separate the different plastics in mixed plastics composition 210. Vibrator 211 produces vibrations that are sufficient to cause the plastics to slide down sorting platform 201 at different velocities at a selected temperature.

[0049] Kinetic frictional plastics sorter 200 has numerous advantageous and unexpected benefits and uses. In an embodiment, a process for kinetic frictional separating plastic species in a mixed plastics composition 210 with a kinetic frictional plastics sorter 200 includes: providing a mixed plastics composition comprising a first plastic and a second plastic, wherein the first plastic has a smaller coefficient of kinetic friction than the second plastic; heating the mixed plastics composition to a first temperature sufficient to spatially separate different plastics in the mixed plasticscomposition due to the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; disposing the mixed plastics composition on a sorting platform arranged at an inclination angle with respect to a support base; allowing the plastics in the mixed plastics composition to slide down the sorting platform under the action of gravity at different velocities that depend on the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; collecting the first plastic in a first collector at a first time; and separately collecting the second plastic in a second collector at a second time that is subsequent to the first time, wherein the first time and the second time for separately collecting the first plastic and the second plastic is based on their respective velocities. In an embodiment, the first plastic is polyethylene, and the second plastic is polypropylene. In an embodiment, the first plastic is polystyrene, and the second plastic is polyethylene. In an embodiment, the first plastic is polyvinyl chloride, and the second plastic is polyethylene. In an embodiment, the first plastic is a recycled plastic, and the second plastic is a virgin plastic. In an embodiment, the first plastic is a colored plastic, and the second plastic is a clear plastic. In an embodiment, the first plastic is a different size than the second plastic. In an embodiment, the first plastic is a different shape than the second plastic. In an embodiment, the first plastic is a different density than the second plastic. In an embodiment, the first plastic is a different chemical composition than the second plastic.

[0050] The kinetic frictional plastics sorter 200 separates different plastics in mixed plastics composition 210. Kinetic frictional plastics sorter 200 includes sorting platform 201 disposed on support base 203, heater 202 in thermal communication with sorting platform 201 , and vibrator 211 in mechanical communication with sorting platform 201 . Sorting platform 201 is arranged at inclination angle 204 with respect to support base 203. Heater 202 heats sorting platform 201 to a first temperature sufficient to spatially separate different plastics in mixed plastics composition 210. Vibrator 211 produces vibrations that are mechanically communicated to sorting platform 201. The vibrations cause the plastics in mixed plastics composition 210 to slide down sorting platform 201 at different velocities that depend on the kinetic coefficients of friction between sorting platform 201 and each different type of plastic 206 in mixed plastics composition 210. The velocity of a first plastic 206.1 is greaterthan the velocity of the second plastic 206.2 at the first temperature so that the first plastic 206.1 is spatially separated from the second plastic 206.2 on sorting platform 201.

[0051] The process for sorting with kinetic frictional plastics sorter 200 can include various steps. Mixed plastics composition 210 is placed on sorting platform 201. Sorting platform 201 is heated to the first temperature by heater 202. Vibrator 211 produces vibrations that are mechanically communicated to sorting platform 201. The plastics in mixed plastics composition 210 slide down sorting platform 201 at different velocities that depend on the kinetic coefficients of friction between sorting platform 201 and each different type of plastic 206 in mixed plastics composition 210. The first plastic 206.1 is spatially separated from the second plastic 206.2 on sorting platform 201. The first temperature is a temperature sufficient to spatially separate different plastics in mixed plastics composition 210. The vibrations produced by vibrator 211 are of a magnitude and frequency sufficient to cause the plastics in mixed plastics composition 210 to slide down sorting platform 201 at different velocities. Sorting platform 201 is inclined at an angle sufficient to allow the plastics in mixed plastics composition 210 to slide down sorting platform 201 .

[0052] In an embodiment, a process for kinetic frictional separating plastic species includes: tilting a surface with respect to the horizontal so that the angle is above the critical angle for the mixed plastics to slide down the incline at the set temperature of the surface; setting and maintaining the temperature of the surface so that the coefficient of kinetic friction between the surface and first plastic to be separated out from the mix is greater than a set-value; ensuring this set-temperature of the surface is such that the coefficient of friction of the other plastics in the mix is less than the friction-set-value; placing the mixed plastics on the inclined and heated surface, wherein placement can be performed by a hopper, a conveyor, blower or manually, and the mixed plastic can be in the form of flakes, pellets, or molded or extruded pieces; optionally vibrating or shaking the surface; allowing the mixed plastic flakes to move down the surface under the action of gravity, wherein plastic flakes with a coefficient of friction greater than the friction-set-value will travel down the incline with an average velocity that is less than those with coefficient of friction less than the friction-set-value; collecting the flakes that have fallen off the bottom edge of thesurface after a set time and placing them in a container; and collecting the flakes that are still on the surface after this set time and placing them in a separate container. The process can be operated recursively, wherein flakes of plastic 206 that have fallen off the lower edge of sorting platform 201 are disposed on a subsequent surface whose temperature is greater than the first temperature to separate out another plastic.

[0053] Sorting platform 201 can be set to a temperature such that the coefficient of kinetic friction between sorting platform 201 and first plastic 206.1 to be separated out from mixed plastics composition 210 is less than a friction-set-value while the coefficient of friction of the other plastics 206 in mixed plastics composition 210 can be greater than this friction-set-value.

[0054] Under conditions of temperature, incline, or vibration, plastics 206 with larger coefficients of kinetic friction move at a slower velocity down sorting platform 201 and travel less distance down sorting platform 201 than plastics 206 whose melting point is above the temperature of sorting platform 201. The plastics 206 in mixed plastics composition 210 move down sorting platform 201 under the action of gravity. Flakes of plastic 206 with a large coefficient of friction will travel down sorting platform 201 more slowly than flakes of plastic 206 with lower coefficients of friction. The flakes of plastic 206 to be separated out from mixed plastics composition 210 can be removed from sorting platform 201 by physical means such as a blower, sweeper, scraper, manual hand removal, and the like or by gravity such as by falling off the end of sorting platform 201 .

[0055] Kinetic frictional separating plastic species in mixed plastics composition 210 can be performed recursively. Remaining flakes of plastic 206 in mixed plastics composition 210 can be separated by the same process, but at a higher temperature such that the coefficient of friction between sorting platform 201 and the next plastic 206 to be separated out from the remaining amount of mixed plastics composition 210 is greater than a friction-set-value while at this set-temperature, the coefficient of friction of the other plastics 206 in mixed plastics composition 210 can be less than the friction-set-value. Plastic flakes that have not been separated via the process can be removed from sorting platform 201 and collected. The plastics 206 that are separated by the process are referred to as sorted plastics.

[0056] In an embodiment, kinetic frictional separating plastic species is a batch process.

[0057] It is contemplated that the process separating plastics 206 in mixed plastics composition 210 can be a continuous process. Here, a process for kinetic frictional separating plastic species includes: tilting a conveyor belt, so that all rollers and pulleys of the conveyer belt are inclined at identical angles with respect to the horizontal; setting the angle of the conveyor belt with respect to the horizontal at an angle such that it is greater than the critical angle at which motion of the plastic flakes down the incline will occur at the set temperature, wherein the geometry is such that in the absence of conveyor belt motion, the flakes would move down the incline in a direction parallel to the long axes of the rollers; setting and maintaining the temperature of the conveyor belt so that the coefficient of kinetic friction between the surface and first plastic to be separated out from the mix is greater than a set-value, such that the temperature of the surface provided the coefficient of friction of the other plastics in the mix to be less than the friction-set-value; disposing the mixed plastics on the inclined and heated surface, wherein the disposal can be performed by a hopper, a conveyor, blower or manually, or the mixed plastic may be in the form of flakes, pellets, or molded or extruded pieces; setting the speed of the heated-tilted conveyor belt so that the plastics with large coefficient of friction will convey to the end of the belt while the plastics with lower coefficients of friction will slide down the incline of the belt and fall off its lower edge, wherein the plastic flakes with a coefficient of friction greater than the friction-set-value will travel down the incline at a relatively lower velocity and will exit the belt at its end (such can be collected in a separate container); and collecting, in separate containers, the plastics the convey off the end of the belt, and those that slide off the lower edge of the belt.

[0058] In mechanical recycling of mixed-composition plastics, it can be advantageous to sort plastics by type. Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species provide a friction-based sorting of plastics according to melting points of the individual species of plastics, wherein there is a strong increase in friction that occurs just below such melting points. In an embodiment, flakes, or pellets of plastics 206 are present in mixed plastics composition 210 that is disposed on sorting platform 201 and conveyed such thatfriction modulates velocity of the individual species of plastics 206. The temperature of sorting platform 201 is set such that the friction strongly modulates the motion of plastics 206 near their melting points, with less modulation to those plastics 206 with melting points well-above the set temperatures. Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species can be used with other sorting technologies.

[0059] A difficulty in recycling plastics is that plastics in curb-side recycling are composed of mixtures of different types of plastics. Mechanical recycling can involve sorting the plastics by type. For some applications, a single species of plastics is preferred over a combination of different types of plastics. Sorted plastics can provide better processing and more consistent product quality as compared with unsorted, mixed plastics composition 210. Conventional technology for sorting mixed plastics include manual sorting, spectroscopy, and density separation that sort according, e.g., to IR spectral signature, density, or shape of different types of plastics. However, certain plastics, e.g., plastics referred to as polyolefins (such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or isotactic polypropylene (iPP)) can be difficult to sort from each other using conventional technology. Beneficially, kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species involves friction, e.g., the kinetic coefficient of friction, with the plastic melting temperatures (referred to as melting points) as parameters to sort plastics. Advantageously, different plastics have different melting points, and the coefficients of friction have a very strong increase as function of temperature just below their melting points. Accordingly, mixed plastics composition 210 is heated to a temperature that is just below the melting point of the lowest melting point plastic in mixed plastics composition 210. It is contemplated that kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species can be used for recycling or reclaiming post-consumer or post-industrial plastics. The sorted plastics can then be re-processed. In an embodiment, a sorted plastic is formed into pellets that are subjected to molding, extrusion, or thermoforming to make various plastic products, e.g., plastic articles, plastic parts, consumer goods, packaging, and the like.

[0060] In an embodiment, kinetic frictional plastics sorter 200, kinetic frictional separating plastic species, control thereof and the like can include the properties, functionality, hardware, and process steps described herein and embodied in any of the following non-exhaustive list: a process (e.g., a computer-implemented method including various steps; or a method carried out by a computer including various steps); an apparatus, device, or system (e.g., a data processing apparatus, device, or system including means for carrying out such various steps of the process; a data processing apparatus, device, or system including means for carrying out various steps; a data processing apparatus, device, or system including a processor adapted to or configured to perform such various steps of the process); a computer program product (e.g., a computer program product including instructions which, when the program is executed by a computer, cause the computer to carry out such various steps of the process; a computer program product including instructions which, when the program is executed by a computer, cause the computer to carry out various steps); a computer-readable storage medium or data carrier (e.g., a computer-readable storage medium including instructions which, when executed by a computer, cause the computer to carry out such various steps of the process; a computer- readable storage medium including instructions which, when executed by a computer, cause the computer to carry out various steps; a computer-readable data carrier having stored thereon the computer program product; a data carrier signal carrying the computer program product); a computer program product including comprising instructions which, when the program is executed by a first computer, cause the first computer to encode data by performing certain steps and to transmit the encoded data to a second computer; or a computer program product including instructions which, when the program is executed by a second computer, cause the second computer to receive encoded data from a first computer and decode the received data by performing certain steps.

[0061] It should be understood that the calculations of parameters, process control, and the like can be performed by any suitable computer system, such as that diagrammatically shown in FIG. 7. Data is entered into system 100 via any suitable type of user interface 116, and may be stored in memory 112, which may be any suitable type of computer readable and programmable memory and can be a non- transitory, computer readable storage medium. Calculations are performed by processor 114, which may be any suitable type of computer processor and may be displayed to the user on display 118, which may be any suitable type of computer display. Processor 114 may be associated with, or incorporated into, any suitable type of computing device, for example, a personal computer or a programmable logic controller. The display 118, the processor 114, the memory 112 and any associated computer readable recording media are in communication with one another by any suitable type of data bus, as is well known in the art. Examples of computer-readable recording media include non-transitory storage media, a magnetic recording apparatus, an optical disk, a magneto-optical disk, and / or a semiconductor memory (for example, RAM, ROM, etc.). Examples of magnetic recording apparatus that may be used in addition to memory 112, or in place of memory 112, include a hard disk device (HDD), a flexible disk (FD), and a magnetic tape (MT). Examples of the optical disk include a DVD (Digital Versatile Disc), a DVD-RAM, a CD-ROM (Compact Disc- Read Only Memory), and a CD-R (Recordable)ZRW. It should be understood that non- transitory computer-readable media include all computer-readable media except for a transitory, propagating signal.

[0062] Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species have several advantages over conventional sorting methods and devices. For example, the vibrator helps to break up clumps of plastic, which can improve the efficiency of the sorting process. The vibrations can help to loosen plastic that is stuck to the sorting platform, which can also improve efficiency. The vibrations can help to prevent plastic from sticking to itself, which can reduce the amount of waste produced by the sorting process. In addition, the vibrator can be used to control the speed at which plastic travels down the sorting platform. This can be useful for sorting plastics with different melting points, as it allows the user to ensure that each type of plastic is heated to the correct temperature before it is sorted. Moreover, Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species can besimple to operate and do not require the use of any chemicals or solvents. Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species are efficient and can separate large quantities of plastic in a short period of time. Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species are versatile and can separate a wide variety of different types of plastic. Kinetic frictional plastics sorter 200 and kinetic frictional separating plastic species can remove contaminants from plastic materials, which can improve the quality of the recycled plastic.

[0063] The articles and processes herein are illustrated further by the following Examples, which are non-limiting.EXAMPLESExample 1. Batch Processing Mixed Plastics.

[0064] A composition that includes low-density polyethylene flakes and high-density polyethylene flakes is sorted to obtain nearly pure low-density polyethylene flakes and nearly pure high-density polyethylene flakes. The flakes of the composition are disposed on a metal surface. The surface is 1 m x 1 m. The surface is heated to a temperature of 110 °C. The angle of the surface with respect to the horizontal is set to 30 °. The mixed flakes are placed along the upper edge of the surface and allowed to start sliding down it. After two seconds, the high-density polyethylene flakes fall off the bottom of the surface and are collected. At this two seconds, the low-density polyethylene flakes that travel slower remain on the surface. The original composition is now sorted into high- and low-density polyethylene.Example 2. Continuous Processing of Mixed Plastics.

[0065] A composition of low-density polyethylene flakes and high-density polyethylene flakes is sorted by species. Flakes of the composition are disposed on a conveyor belt whose outer surface is coated Teflon. The surface is two meters long and one meter wide. The surface of the conveyer belt is maintained at 117°C. The angle of the long axes of the rollers and pulleys of the conveyor belt with respect tothe horizontal is set to 30 °. The velocity of the belt is 1 m / s. The flakes of composition are disposed proximate to the upper-most edge of the conveyor belt and the tail pulley. The high-density polyethylene flakes slide down the incline of the conveyor belt and are collected. The low-density polyethylene flakes slide more slowly, remain for a longer time on the conveyor belt, are removed from the conveyor belt at the far end of the conveyor belt, and are collected in a separate container. As a result, the composition is sorted into isolated collections of high-density polyethylene and low- density polyethylene. The conveyor belt velocity is adjusted to optimize and change sortation.Example 3.

[0066] Described herein is a novel solution to producing sufficiently high purity recyclates. The kinetic coefficient of friction of solid plastics near their melting points is used for sorting. Despite the maturity of the field of tribology, conventional technology is deficient in quantitative measurements of kinetic friction of thermoplastics in the regime relevant to low applied pressure. For polyolefins examined, substantial upturns in friction occur near the melting point. For the PET, a huge peak in friction occurs as a function of temperature, which is ascribed to coldcrystallization effects. The innovation described herein is useful, e.g., as a method for post-consumer resin sortation.

[0067] Sortation is involved in mechanical recycling of post-consumer plastics (PCR) whereby properties such as density or spectral signature are used to separate plastics. However, it is difficult to sort polyolefin flakes at high throughput by these properties. We ask whether the frictional properties of plastics as a function of temperature may be used as an alternate sorting property, but fundamental studies of friction at elevated temperatures are limited. Here, we describe the temperature dependence of kinetic friction for three common polyolefins (high- and low-density polyethylene and polypropylene) as well as for polyethylene terephthalate (PET), focusing on the softening / melting regime. The results are augmented by differential scanning calorimetry and dynamic modulus temperature scans. For the polyolefins, we find strong increases in the coefficients of kinetic friction during temperature rampsin the softening regime. For the PET, we report a notable peak in the kinetic friction which we associate with the glass transition and cold crystallization.

[0068] The international efforts to increase plastics recycling rates are driven to reduce plastic pollution, to keep valuable materials within the working economy, and to reduce greenhouse gas emissions. The workhorse method is mechanical recycling (MR). To maximize performance of recyclates, the input plastics can first be sorted by type. In polyolefins, blending of thermodynamically immiscible polymers such as isotactic polypropylene (iPP) and high-density polyethylene (HDPE) can result in materials with reduced tensile properties. Such mixing reduces the economic value of the recyclate and hence the recycling rates.

[0069] In MR, the quality of the recyclate is dependent on the degree to which the plastic has been sorted into its constituent types. For post-consumer recycling, the plastics typically undergo a series of steps that include including cleaning, sorting, and grinding into flakes before they are remelted in an extruder and pelletized for subsequent use. Automated sorting schemes make use of some property of the plastics that allows differentiation in the recycling facilities including differences in near-infrared spectra, density (float-sink sorting) or shape. Research proceeds apace on development of sorting technologies based on other means, such as tribocharging, incorporation and sensing of tracers, selective grinding, magnetic density separation, artificial intelligence, and hyperspectral imaging.

[0070] In the case of polyolefins, the float-sink step separates the polyolefins from most other common plastics, such as polyethylene terephthalate (PET), but does not separate the various polyolefins from each other because they all have densities less than 1 g / cm3 and thus all floats. Thus, isotactic polypropylene (iPP), high density polyethylene (HDPE) and low-density polyethylene (LDPE) may be difficult to sort from each other.

[0071] Here, sortation is based on the differences in melting points between different plastics and differences in physical properties at or near the melting points. Various classes of polyolefins and polyethylene terephthalate (PET) constitute 79% by mass of plastic waste in the United States. As the three polyolefins listed above are well known to have melting temperatures that differ by tens of degrees Kelvin fromeach other, the melting point provides a natural consideration as a handle by which to sort. However, bringing the plastics to or above their melting point may be difficult as different flakes will adhere to each other on conveyor belts. Consider property changes that occur in the pre-melting region where some properties, such as crystallization and modulus, exhibit decreases in value compared to room temperature. As the pre-melting, or softening, region can be 10 °C in width, it may be accessible in a reprocessing operation. This Example describes the temperature dependence of the kinetic coefficient of friction (pk), also referred to here as CoF, of four commodity polymers (HDPE, LDPE, iPP, and PET). Because the temperature dependence of the coefficients of friction between different polymers differs sufficiently, especially near melting points, it can be used in sortation or purification of a composition of plastics.

[0072] The kinetic friction between polymers and metal surfaces and the frictional forces are ascribed to both adhesive and viscoelastic properties. The segmental a relaxation region signifies Tg. In other works, the region near the melting point was examined for ball-on-disc frictional measurements of HDPE, iPP, and their blends, wherein strong increases in the frictional force near the melting point was found and correlated with strong decreases in modulus. However, those measurements did not reduce this force to a coefficient of kinetic friction, perhaps due to the plowing of the ball into the polymer near the melting points. Such plowing can produce a confounding effect on the frictional force, making a reduction to coefficient of friction problematic. Other works on polyolefins in the pre-melting region were conducted via plate-on-wheel geometry, to gain insights on the melting process of pellets in extrusion. These works found an increase in the kinetic coefficient of friction (CoF) near the melting point in some cases, but not others. For example, for LDPE pk increases from pk « 0.1 for T < 60 °C up to pk « 0.3 near T « 125 °C, at the onset of mechanical melting, though under other conditions, and there was no increase in pk near the melting point.

[0073] PET is distinct from the above polyolefins from the perspective of crystallization because its glass transition temperature is above room temperature. Thus, in typical manufacturing conditions when it is cooled rapidly below its glass transition temperature (Tg « 70 °C), crystallization will cease for molecular mobilityreasons before it is thermodynamically complete. When subsequently reheated above its Tg yet below its melting temperature (Tm), it will undergo significant additional crystallization, known as cold crystallization.

[0074] Temperature dependent friction studies of PET are scarce. Using an atomic force microscope, some have used temperature-controlled force microscopy to measure friction force for several polymers including PET and found a peak in the ratio of the loss to storage moduli (tan(b)) near the bulk Tg although no corresponding increase in the frictional force occurred at these temperatures. Although there are no known measurements in bulk systems of the effects of cold crystallization on kinetic friction, we show that the effects are large.

[0075] Experimental

[0076] Friction experiments are conducted on a torsional rheometer with a ring-on-plate tribology fixture (rotating steel-ring on stationary plastic plate). The ring- on-plate geometry reduces the plowing effect that is observed in pin-on-disc or ball- on-disc measurements when the material becomes sufficiently soft. The outer diameter of the ring is 31.70 mm, and its width is 1.38 mm. The experiments were conducted at fixed sliding velocities (vs), as specified for each experiment and always with a nominal fixed temperature ramp of 3 °C / min starting near room temperature. The temperature ramp was achieved through the rheometer’s forced convection oven accessory. The temperature ramp induces a small temperature lag between the instrument’s temperature measurement point and the sample. The magnitude of this effect is found via one-time temperature measurement during a temperature ramp with a thin-wire thermocouple positioned be-tween sample and ring in the absence of ring rotation and a correction is applied to the temperature data. This correction increases with temperature and reaches 3.1 °C at T = 160°C.

[0077] The control of axial normal force FN (and hence P = FN / A, where A is the area of the ring) is facilitated through an axial spring in the shaft. This allows the rheometer to set and maintain a given axial normal force (FN) through a feedbackloop. In most experiments reported here, we utilize FN = 1 N and we find the rheometer maintains normal force control within 10 % of a given set-point (See FIG. 8) until the sample becomes molten (discussed below). At worst, for our lowest employed valueof FN = 0.1 N, the control decreases to 25 % of the set point force (control improves for FN > 1 N). In addition to monitoring the axial force, we also monitor the gap, and change in gap (5h).

[0078] The kinetic coefficient of friction (CoF) is calculated via the relation pk = FF / FN where FF is the kinetic friction force calculated simply from the measured torque and geometrical considerations. To compare the temperature dependencies of CoF between different plastics, measurements were conducted for each type at a constant sliding speed vs = 5 mm / s and a constant pressure P = 15 kPa during temperature ramps. To measure the effects of P and vs, additional experiments were conducted on HDPE - measurements were conducted at five pressures for fixed vs, and at four vs for fixed P.

[0079] The effects of friction induced interfacial heating have been considered in a heat conduction model to estimate the interface temperature, and modest temperature increase occurs due to interfacial heating, for example, under conditions of P = 3.45 MPa and vs = 305 mm / s and T = 100 °C they found a temperature increase of « 5 °C. The interfacial heating is proportional to both P and vs. As our nominal pressure is approximately 103 times less than that employed by Spalding and coworkers, and our nominal vs is « 50 times less, we do not anticipate that interfacial heating will play an important role in the current experiments.

[0080] We utilized post-consumer resins that were acquired from household waste - they were identified by their recycling codes. Sections from these items were cut into 35 mm test samples for adhering onto the test fixtures. For PET (resin code #1 ) we used cutouts from a clamshell food container, for HDPE (#2) milk jug, for LDPE (#4) lids from a takeout food container, and for iPP (#5) yogurt cups. One side of a sample is lightly roughened with sandpaper, coated with high temperature epoxy, and then adhered onto disposable bot-tom plates and allowed to cure overnight. In the employed protocol, samples are not brought above room temperature before the beginning of the test, so thermally speaking, the state of the sample is set by the processing operations (e.g., injection molding) that produced the household items. Prior to measurement, the surface of the metal ring was lightly sanded with high grit paper and then rinsed with tap water, to remove possible contaminates from prior experiments. The sample was rinsed with water.

[0081] Measurements of friction near the melting point can consider the domain of experimental stability. FIG. 8 shows the torque, change in gap 5h, and axial loading (FN) during a temperature ramp at constant angular ring rotation. As seen in FIG. 8A, FF increases steadily until a temperature of T = 115 °C where it becomes unstable. FIG. 8B shows the change in 5h from the start of the experiment. This quantity shows a steady increase from the start of the experiment until T = 120 °C. The increase is attributed to thermal expansion that occurs naturally in the semicrystalline state as temperature is increased, including that attributed to the reduction in crystallinity as the melting point is approached. At the temperature of T = 120° C, slightly above the temperature of the FF instability, 5h decreases suddenly. This is reminiscent of the plowing effect in pin-on-disc measurements and is attributed to the normal force pressing the slider down into the increasingly soft (or molten) plastic. In FIG. 8C, the rheometer can maintain axial normal force control until the temperatures at which 5h has its precipitous drop. In practice, in the remaining CoF plots, we discard data points at temperatures beyond the onset of this instability.

[0082] As noted, the pressures utilized in the current experiments are less than those simulating conditions in an extruder. This may be significant in the region where the plastic is softening, as the rotating ring will be less likely to cause abrasion and less likely to plow into the plastic. This will allow the experiments to proceed to higher temperatures - closer to the melting point than the extrusion simulation experiments.

[0083] Differential Scanning Calorimetry (DSC) measurements were conducted under a dry nitrogen purge equipped with a mechanical chiller. Heat flow and temperature calibration were performed. Temperature calibration was performed using adamantine, benzophenone, indium, tin, and lead standards. All measurements were performed at heating rates of 3 K / min on samples of « 8 mg.

[0084] Dynamic tensile measurements as a function of temperature were carried out on a dynamic mechanical analyzer using a tensile fixture in a forced convection oven. Measurements were carried out at the same ramp rate of (3 °C / min) on strips of width 12.5 mm and length 20 mm and thickness ranging from (0.34 to 0.7) mm depending on the plastic. As the melting point is approached, the moduli decrease, and the specimens eventually start to creep. For the three polyolefins, the creepremains less than 10 % strain in the presented data while for PET, it can exceed that as discussed later. Measurements were conducted at a frequency of 10 rad / s in proportional force tracking mode with the target oscillation amplitude set at 0.02 %.

[0085] Results

[0086] FIG. 9 shows the combined results of the friction measurement, the DSC, and the tensile moduli for LDPE. The CoF data is derived from that shown in FIG. 8(A and C) and is reported for temperatures below the instability points, as described above. It shows a value for the CoF of pk « 0.14 until T « 40 °C and then begins trending upwards at an increasing rate with temperature. At T « 105° C there is a sharper upturn in slope of pk vs. T. We note that reports of pk > 1 for such thermoplastics have not been reported to our knowledge and for this sample, that point is reached at T = 95 °C. Indeed, we find pk > 3 at the point of instability.

[0087] Concomitant with the increase in pk, we note steady decreases in both the crystallinity (FIG. 9B) and the linear viscoelastic dynamic moduli, namely the storage (E’) and loss (E”) moduli (FIG. 9C). At the point of the instability of pk, the crystallinity has dropped to 23 % by mass, indicating that for the large values of pk reported here, the sample is still in a semi-crystalline state. Further, the mechanical moduli also indicate that the sample can still be considered solid-like, as E ' > E ' ' . Note the precipitous drop in the tensile moduli just at the point of CoF instability. At the point of the instability, we find E ' « 15 MPa, which is approximately 50 times less than that at T = 40 °C.

[0088] Next, we consider iPP (FIG. 10), which has the highest value of Tm amongst the polyolefins considered here. The overall trend has similarities to LDPE, however the shapes of the two CoF curves are dissimilar - whereas LDPE shows a continuous increase in pk over an extended temperature range, that for iPP is relatively flat, pk < 0.25 for T < 145 °C, which is then followed by a sharp upturn at around T = 155 °C - near the melting point. This difference in shape is reflected in the shapes of the crystallinity and moduli curves (FIG. 10B and FIG. 10C, respectively). Whereas the crystallinity for the LDPE decreases by 22 % from 50 °C to 100 °C, for iPP it decreases by only 5 % over the same temperature window. Similarly, the modulus of iPP is greater over this temperature window and its slope with respect totemperature is less - we return to this later. For the iPP, the maximal value of the CoF is less than LDPE (and less than the other two polyolefin samples). This is likely due to an adhesion problem between the iPP and the lower substrate - this limited the maximum temperature that could be achieved before the experiment became unstable.

[0089] FIG. 11 shows the case of HDPE. The overall shape of the curved mirrors that of iPP in that the CoF and crystallinity are flat in the temperature region window below that where the crystallinity drops; pk < 0.13 for T < 120 °C. The strong upturn in CoF starts at around T = 120 °C which is about 15 °C below the melting point and reaches a peak value of pk = 4.1 before the instability occurs.

[0090] The effects of pressure and sliding velocity on the CoF for the case of HDPE are considered. In FIG. 12A, vs is varied at a fixed pressure (P) while FIG. 12B shows the opposite case. In both cases, the effect of sliding velocity (or pressure) is relatively weak at temperatures well below the melting point of HDPE, consistent with the findings already described in FIG. 11 A for the specific case of vs = 5 mm / s and P = 15 kPa. The results in this regime are broadly consistent with the simplest model of friction where the CoF is independent of velocity and pressure. The upturn in CoF becomes progressively stronger as vs is increased from (5 x 10-3 to 5) mm / s. The upturns in COF are not seen until temperatures exceed roughly T = 130 °C, consistent with the previous results shown for the single case of vs = 5 mm / s. Also note that there is a strong dependence of CoF on sliding velocity. Such a trend in this dependency has been seen previously in the case of rubber on granite.

[0091] FIG. 12B shows five pressures for the sliding velocity of vs = 5 mm / s. The upturn appears to become progressively stronger at lower pressures. We point out that some of this effect may be due to the softening of the material at the elevated temperatures, and this effect becomes exacerbated at higher pressures. This result is consistent with friction studies mentioned previously that were conducted at higher pressures and showed smaller (or no) increase in CoF near the melting point. One can also consider that the point of instability is greater for the higher pressures, and thus for the lower pressures, the experiments can proceed to higher temperatures before instability. Further, one can consider that the plowing effect, or a material grinding effect may be more likely to occur at the higher pressures as the materialbecomes soft at these elevated temperatures. Nevertheless, if one fixes on a temperature in the upturn region, (say T = 133 °C), one can see that the CoF increases from 1 .2 at the highest pressure to 3.8 at the lowest.

[0092] PET differs from the three previously examined polyolefins in that its Tg is above room temperature and under typical industrial processing conditions, it is cooled below the glass transition temperature be-fore crystallization completes, as mentioned above. Here, the DSC shows the crystallinity at the start of the heating ramp is 22.5 % (FIG. 13B). The glass transition can be seen at T « 70 °C and that cold crystallization commences at T = 120 °C. The cold-crystallization manifests as a near doubling of the crystallinity over the temperature range from T = (120 to 140) °C. The transition of PET from semi-crystalline to molten state occurs at T « 260 °C.

[0093] The effects of Tg and crystallization can also be seen in the mechanical moduli (FIG. 13C). The glass transition temperature is seen as the peak in E" that occurs at T = 76 °C. As the sample is brought further above its Tg, the moduli drop by over two orders of magnitude. When the plastic reaches a temperature of T = 120 °C and cold crystallization commences, the moduli increase by over one order of magnitude. The mechanical measurement is challenging over this extended low modulus region because of sample creep.

[0094] The dashed vertical line at T = 117 °C represents the point at which the relative change in length of the sample exceeds 10 % - values at temperatures that exceed this may be considered qualitative. The optical appearance of the sample changes during the cold crystallization process, morphing from transparent to white - consistent with increased crystallinity. The CoF for PET shows a pronounced peak as a function of temperature, as clearly seen in FIG. 13A. Deviations from the room temperature values start at T « 80 °C; this value is slightly above the Tg observed in the thermal and mechanical curves. The CoF reaches a peak at T « 110 °C and then starts to decrease. Interestingly, the decrease starts at a temperature slightly lower than the start of the cold-crystallization (as seen from the DSC) and lower than the upturn in the mechanical moduli. The CoF continues to decrease until it levels off at T « 130 °C, which is near the temperature at which the cold-crystallization process has completed for this set of conditions.

[0095] Similar behavior was found for the coefficient of friction as a function of temperature regardless of the surface roughness. The milk jug is designed to have some regions that are relatively smooth and others that are textured, but it has the same qualitative effects.

[0096] The experimental results are summarized in FIG. 13 where the results from four plastics, along with the moduli are placed together. This plot shows that the temperature regions for the high friction states for the three polyolefins are well differentiated. We also note that these high friction states are associated with reduced moduli. For example, the horizontal dashed line in FIG. 14B is drawn at E ' = 2 MPa - well below the room temperature moduli. The corresponding colored vertical dashed lines connect to the corresponding CoF for each plastic type. This value is in all cases associated with the high friction state. However, we do not discern from the data a unique relationship between the high friction state and the mechanical moduli.

[0097] We can gain insight to these high-friction states near the melting point by considering rubber, whose kinetic friction coefficients can exceed 1 , with values up to 8. In a rubber the material is above Tg, has moduli from 100 MPa to 102 MPa, has zero or low crystallinity and can contain fillers. For the plastics examined in this work, the high-friction states correspond similarly to low moduli states, crystallinity below 30 % and CoFs that exceed 1 . A simple picture is that the reduced crystallinity at elevated temperatures causes reduced moduli, which then give the material a rubber-like mechanical moduli. Rubbers maintain their elasticity through chemical crosslinking. For semi-crystalline thermoplastics just below the melting point, it is the crystalline domains, linked into a network by amorphous domains that act as effective crosslinks and provide the material with rubber-like properties.

[0098] During sliding, the metal substrate has asperities, and these produces local oscillations on the rubber surface that lead to cyclic de-formations and energy dissipation in the rubber, causing high levels of CoF. This could create the high friction state in the plastics as well. Rubbers can exhibit strong variations in their CoF as a function of sliding velocity as attributed to dissipative mechanisms. This notion provides motivation for imaging studies of the interface, for example to search for Schallamach waves.

[0099] The processes described herein can be embodied in, and fully automated via, software code modules executed by a computing system that includes one or more general purpose computers or processors. The code modules can be stored in any type of non-transitory computer-readable medium or other computer storage device. Some or all the methods may alternatively be embodied in specialized computer hardware. In addition, the components referred to herein can be implemented in hardware, software, firmware, or a combination thereof.

[0100] Many other variations than those described herein can be apparent from this disclosure. For example, depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multithreaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines and / or computing systems that can function together.

[0101] Any logical blocks, modules, and algorithm elements described or used in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and elements have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure.

[0102] The various illustrative logical blocks and modules described or used in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a processing unit or processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gateor transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor can include primarily analog components. For example, some or all of the signal processing algorithms described herein can be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.

[0103] The elements of a method, process, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module stored in one or more memory devices and executed by one or more processors, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of non- transitory computer-readable storage medium, media, or physical computer storage known in the art. An example storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The storage medium can be volatile or nonvolatile.

[0104] While one or more embodiments have been shown and described, modifications and substitutions can be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the presentinvention has been described by way of illustrations and not limitation. Embodiments herein can be used independently or can be combined.

[0105] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. The ranges are continuous and thus contain every value and subset thereof in the range. Unless otherwise stated or contextually inapplicable, all percentages, when expressing a quantity, are weight percentages. The suffix (s) as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including at least one of that term (e.g., the colorant(s) includes at least one colorants). Option, optional, or optionally means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event occurs and instances where it does not. As used herein, combination is inclusive of blends, mixtures, alloys, reaction products, collection of elements, and the like.

[0106] As used herein, a combination thereof refers to a combination comprising at least one of the named constituents, components, compounds, or elements, optionally together with one or more of the same class of constituents, components, compounds, or elements.

[0107] All references are incorporated herein by reference.

[0108] The use of the terms "a," "an," and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. It can further be noted that the terms first, second, primary, secondary, and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. It can also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements, these elements should not be limited by these terms. For example, a first current could be termed a second current, and, similarly, a second current could be termed a first current, without departing from the scope of the various described embodiments. The first current and the second current are both currents, but they are not the same condition unless explicitly stated as such.

[0109] The modifier about used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). The conjunction or is used to link objects of a list or alternatives and is not disjunctive; rather the elements can be used separately or can be combined under appropriate circumstances. / / PARTS LIST / / kinetic frictional plastics sorter 200 sorting platform 201 heater 202 support base 203 inclination angle 204 collector 205 plastic 206 vibrational direction 207 vibrational frequency 208 separating direction 209 mixed plastics composition 210 vibrator 211 kinetic frictional separating plastic species / / kinetic frictional separates plastic species

Claims

What is claimed is:1 . A kinetic frictional plastics sorter 200 for kinetic frictional separating plastic species in a mixed plastics composition 210, the kinetic frictional plastics sorter 200 comprising: sorting platform 201 disposed on support base 203 and in thermal communication with heater 202 and in mechanical communication with support base 203 and that is arranged at inclination angle 204 with respect to support base 203, is heated by heater 202 to a first temperature sufficient to spatially separate different plastics in mixed plastics composition 210, receives mixed plastics composition 210, such that plastics in mixed plastics composition 210 slide down sorting platform 201 under the action of gravity at different velocities that depend on the kinetic coefficients of friction between sorting platform 201 and each different type of plastic 206 in mixed plastics composition 210, and the velocity of a first plastic 206.1 is greater than the velocity of the second plastic 206.2 at the first temperature so that the first plastic 206.1 is spatially separated from the second plastic 206.2 on the sorting platform 201 ; heater 202 in thermal communication with sorting platform 201 and that heats mixed plastics composition 210 disposed on sorting platform 201 to the first temperature to provide spatial separation of the different plastics in the mixed plastics composition 210 due to the kinetic coefficients of friction between sorting platform 201 and each different type of plastic 206 in mixed plastics composition 210; and mixed plastics composition 210 comprising a first plastic 206.1 and a second plastic 206.2, such that first plastic 206.1 has a smaller coefficient of kinetic friction than the second plastic 206.2 and moves at a greater velocity down sorting platform 201 and travels a greater distance down sorting platform 201 than the second plastic 206.2 whose melting point is greater than the first temperature of the sorting platform 201.

2. The kinetic frictional plastics sorter 200 of claim 1 , further comprising support base 203 on which is disposed sorting platform 201 and in mechanical communication with sorting platform 201 and that receives sorting platform 201 and provides amechanically supportive base so that sorting platform 201 can be inclined at inclination angle 204 with respect to support base 203.

3. The kinetic frictional plastics sorter 200 of claim 1 , further comprising collector 205 in communication with sorting platform 201 and that receives separated species of plastic 206 from mixed plastics composition 210 that are kinetic frictionally separated on sorting platform 201 , such that a first collector 205.1 collects a first plastic 206.1 and a second collector 205.2 collects a second plastic 206.2.

4. The kinetic frictional plastics sorter 200 of claim 1 , further comprising vibrator 211 in mechanical communication with sorting platform 201 and that produces vibrations that are mechanically communicated to sorting platform 201 , such that sorting platform 201 is subjected to the vibrations.

5. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is polyethylene, and the second plastic is polypropylene.

6. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is polystyrene, and the second plastic is polyethylene.

7. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is polyvinyl chloride, and the second plastic is polyethylene.

8. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a recycled plastic, and the second plastic is a virgin plastic.

9. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a colored plastic, and the second plastic is a clear plastic.

10. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a different size than the second plastic.11 . The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a different shape than the second plastic.

12. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a different density than the second plastic.

13. The kinetic frictional plastics sorter 200 of claim 1 , wherein the first plastic is a different chemical composition than the second plastic.

14. A process for kinetic frictional separating plastic species in a mixed plastics composition 210 with a kinetic frictional plastics sorter 200, the process comprising: providing a mixed plastics composition comprising a first plastic and a second plastic, wherein the first plastic has a smaller coefficient of kinetic friction than the second plastic; heating the mixed plastics composition to a first temperature sufficient to spatially separate different plastics in the mixed plastics composition due to the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; disposing the mixed plastics composition on a sorting platform arranged at an inclination angle with respect to a support base;sliding the plastics in the mixed plastics composition down the sorting platform under the action of gravity at different velocities that depend on the kinetic coefficients of friction between the sorting platform and each different type of plastic in the mixed plastics composition; collecting the first plastic in a first collector at a first time; and separately collecting the second plastic in a second collector at a second time that is subsequent to the first time, wherein the first time and the second time for separately collecting the first plastic and the second plastic is based on their respective velocities.

15. The process of claim 14, wherein the first plastic is polyethylene, and the second plastic is polypropylene.

16. The process of claim 14, wherein the first plastic is polystyrene, and the second plastic is polyethylene.

17. The process of claim 14, wherein the first plastic is polyvinyl chloride, and the second plastic is polyethylene.

18. The process of claim 14, wherein the first plastic is a recycled plastic, and the second plastic is a virgin plastic.

19. The process of claim 14, wherein the first plastic is a colored plastic, and the second plastic is a clear plastic.

20. The process of claim 14, wherein the first plastic is a different size than the second plastic.

21. The process of claim 14, wherein the first plastic is a different shape than the second plastic.

22. The process of claim 14, wherein the first plastic is a different density than the second plastic.

23. The process of claim 14, wherein the first plastic is a different chemical composition than the second plastic.

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