Apparatus and method for optimizing injection molding parameters, formulations and mold configurations

Abstract

Disclosed are methods and systems for determining mold design, polymer formulation, and processing parameters for forming thermoplastic foams with desired cell structure, mechanical properties, and physical properties. In one example, the system includes a plaque mold and multiple interchangeable mold cavities, including one pair of mold cavities used to form solid polymer test specimens and two or more pairs of mold cavities for forming thermoplastic foam test specimens. The mold cavities have multiple sensors for determining pressure and temperature at various locations within the mold cavities. The test specimens are compared, and decisions are made based on the comparison and evaluation of the data regarding mold design, formulation, and / or processing parameters. Optionally, the disclosed methods and systems can employ an exhaust system and collection system to collect exhaust gases to determine the solubility of a particular polymer and gas combination and further determine mold design, formulation, and / or processing parameters.

Description

[Technical Field]

[0001] The present disclosure relates generally to systems and methods for using an injection molding plaque mold tester to determine and optimize various mold designs, polymer formulations, and processing parameters for forming polymers with specific, preferred physical and mechanical properties. More particularly, the present disclosure relates to systems and methods for using an injection molding plaque mold tester with multiple, interchangeable mold cavities, multiple sensors, and a process for collecting data to determine and optimize mold designs, polymer formulations, and processing parameters for forming thermoplastic foam resins with specific, preferred physical and mechanical properties. [Background technology]

[0002] Thermoplastic foams, also known as porous thermoplastics, are materials with properties that make them useful for many applications. Thermoplastic foams are typically foamed polymers that contain two or more phases: a continuous, solid polymer matrix and a dispersed gas phase. This two-phase structure is formed by gas molecules dispersed in the form of bubbles during the molding process. The gas is trapped in the molded part and forms voids as the polymer solidifies, creating a two-phase structure. Thermoplastic foams have useful properties and characteristics, such as lower weight compared to typical molded polymer parts due to their low density, reduced heat and noise transmission, and resistance to impact and compression.

[0003] The mechanical properties of thermoplastic foams are controlled by their cell structure, including cell uniformity, average cell size, and cell density. These structural properties are determined by mold design, formulation, and processing parameters of the molding process. As is well known, current approaches attempt to determine appropriate mold design, formulation, and processing parameters through traditional trial-and-error methods. Such trial-and-error methods require the creation of multiple molds and numerous experiments, which can be time-consuming and costly to complete. What is needed is an apparatus useful for determining and optimizing mold design, formulation, and processing parameters for forming thermoplastic foams in a manner that reduces time and cost and results in thermoplastic foams with desirable properties, as well as an effective and efficient method for using such an apparatus. The present disclosure describes and illustrates such an apparatus and an efficient method for using the apparatus. Summary of the Invention [Problem to be solved by the invention]

[0004] Disclosed herein is an apparatus and method of using such an apparatus for determining mold design, formulation and processing parameters for forming thermoplastic foam resins having desired cell structure and mechanical and physical properties. [Means for solving the problem]

[0005] In one example, the apparatus is a plaque mold assembly with multiple interchangeable mold cavities, including one pair of mold cavities used to form solid polymer specimens and two or more pairs of mold cavities for forming thermoplastic foam specimens. The mold cavities have multiple sensors for determining pressure and / or temperature at different locations within the mold cavities during the molding process. Once the solid specimens and two or more thermoplastic foam specimens are molded, data collected during the molding process and observations of the resulting specimens are compared, and a decision is made based on the comparison and evaluation of the data regarding optimization of mold design, formulation, and / or processing parameters. Optionally, an exhaust system and collection tank may be used to collect exhaust gases. Collecting the exhaust gases can determine the solubility of a particular polymer and gas combination, which can be combined with other collected data to determine and optimize mold design, formulation, and / or processing parameters. Other optional components include multiple inserts that change the quantity and location of exhaust ports, which affect the release of exhaust gases during the molding process, and multiple gate and runner components that change the way molten polymer is injected into the mold cavity during the molding process.

[0006] The accompanying drawings, in conjunction with the following detailed description, illustrate the structure of exemplary embodiments of the disclosed systems, methods, and apparatus. Like elements are appropriately labeled with the same or similar reference numerals. Elements shown as a single element may be replaced by multiple elements. Elements shown as multiple elements may be replaced by a single element. The drawings may not be to scale. The proportions of certain elements may be exaggerated for illustrative purposes. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a plaque mold with a pair of removable mold cavities within the plaque mold. [Figure 2] FIG. 1 is a schematic diagram of an exemplary test specimen for use in the methods described herein. [Figure 3] FIG. 1 is a schematic diagram of an exemplary pair of mold cavities with test specimens cut from plaques formed during the molding process, the mold cavities designed to produce test specimens 3.2 mm thick. [Figure 4] FIG. 10 is a schematic diagram of an exemplary pair of mold cavities with test specimens cut from plaques formed during the molding process, the mold cavities designed to produce either a 7.0 mm thick test specimen or a 14.0 mm thick test specimen. [Figure 5] FIG. 10 is a schematic diagram of a mold plate with mold cavities arranged to produce a 3.2 mm solid specimen. [Figure 6] FIG. 1 is a schematic diagram of a mold plaque with mold cavities arranged to produce 3.2 mm thermoplastic foam specimens. [Figure 7] FIG. 1 is a schematic diagram of a mold plaque with mold cavities arranged to produce 7.0 mm thermoplastic foam specimens. [Figure 8] FIG. 1 is a schematic diagram of a mold plaque with mold cavities arranged to produce 14.0 mm thermoplastic foam specimens. [Figure 9] FIG. 1 is a schematic diagram of a mold plaque with mold cavities arranged to produce 25.4 mm thermoplastic foam specimens. [Figure 10A] FIG. 10 is a schematic diagram of a 3.2 mm plaque produced in a plaque mold. [Figure 10B] FIG. 10 is a schematic diagram of a 7.0 mm plaque produced in a plaque mold. [Figure 10C] FIG. 10 is a schematic diagram of a 14.0 mm plaque produced in a plaque mold. [Figure 10D] FIG. 10 is a schematic diagram of a 25.4 mm plaque produced in a plaque mold. [Figure 11] 1A-1C are diagrams illustrating possible locations of sensors within a mold cavity. [Figure 12]FIG. 10 is a schematic diagram of a plaque mold with two independent water circulation systems that can be configured. [Figure 13] FIG. 1 is a perspective view showing a schematic diagram of a plaque mold with a collection tank. [Figure 14] FIG. 10 is another perspective view showing a schematic representation of a plaque mold with a collection tank. [Figure 15] FIG. 1 is a perspective view showing a schematic of a pair of collection cylinders used in a plaque mold system. [Figure 16] FIG. 16 is a perspective view showing a schematic diagram of the plaque mold with a pair of collection cylinders of FIG. 15. [Figure 17] FIG. 1 is a perspective view showing a schematic of three collection cylinders used in a plaque mold system. [Figure 18] 18 is a perspective view showing a schematic diagram of the plaque mold with three collection cylinders of FIG. 17. FIG. [Figure 19] FIG. 12 shows a comparison of pressure curves of different saturated polymer mixtures recorded by sensor number 1 in the 14 mm cavity of FIG. [Figure 20] FIG. 12 shows a comparison of pressure curves of different saturated polymer mixtures recorded by sensor number 2 in the 14 mm cavity of FIG. [Figure 21] FIG. 12 shows a comparison of pressure curves of different saturated polymer mixtures recorded by sensor number 3 in the 14 mm cavity of FIG. [Figure 22A] FIG. 10 shows a schematic representation of the flow patterns of a polymer with developed flow properties at different time intervals. [Figure 22B] FIG. 10 shows a schematic representation of the flow patterns of a polymer with developed flow properties at different time intervals. [Figure 22C] FIG. 10 shows a schematic representation of the flow patterns of a polymer with developed flow properties at different time intervals. [Figure 22D] FIG. 10 shows a schematic representation of the flow patterns of a polymer with developed flow properties at different time intervals. [Figure 23]FIG. 1 shows a photograph of the flow behavior of a 14 mm general purpose polystyrene (GPPS) member and an accompanying schematic model. [Figure 24] FIG. 1 shows a photograph of the flow behavior of a 14 mm high impact polystyrene (HIPS) member and an accompanying schematic model. [Figure 25] FIG. 12 shows the temperature curve recorded by sensor number 1 in the 14 mm cavity of FIG. 11. [Figure 26] FIG. 12 shows the temperature curve recorded by sensor number 2 in the 14 mm cavity of FIG. 11. [Figure 27] FIG. 12 shows the temperature curve recorded by sensor number 3 in the 14 mm cavity of FIG. 11. [Figure 28] 1A and 1B are photographs of injection foamed resin parts with different formulations formed in a 14 mm mold cavity. [Figure 29] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 5 cubic inches (approximately 81.9 cm3) / second. [Figure 30] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 10 cubic inches (approximately 163.8 cm3) / second. [Figure 31] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 20 cubic inches (approximately 327.7 cm3) / second. [Figure 32] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 5 cubic inches (approximately 81.9 cm3) / second. [Figure 33] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 10 cubic inches (approximately 163.8 cm3) / second. [Figure 34]FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2, and 3 in the 14 mm cavity of FIG. 11 at an injection rate of 20 cubic inches (approximately 327.7 cm3) / second. [Figure 35] FIG. 12 shows a comparison of pressure curves recorded by sensors number 1, 2 and 3 in the 14 mm cavity of FIG. 11 for different blowing agent concentrations. DETAILED DESCRIPTION OF THE INVENTION

[0008] The apparatus, systems, arrangements, and methods disclosed herein are described in detail, by way of example, with reference to the drawings. It will be understood that the disclosed and described examples, arrangements, configurations, members, elements, devices, methods, materials, and the like are subject to change and may be desirable for particular applications. In this disclosure, identification of specific techniques, configurations, methods, and the like is either related to the specific examples described or is merely a general description of such techniques, configurations, methods, and the like. Identification of specific details or examples is not intended to be, and should not be construed as, essential or limiting unless otherwise specified. With reference to Figures 1-35, selected examples of apparatus and methods of using such apparatus for testing and determining mold designs, formulations, and processing parameters for forming thermoplastic foam resins having certain preferred physical and mechanical properties are disclosed and described in detail.

[0009] Disclosed herein are apparatuses and methods for using such apparatuses for determining and optimizing mold design, formulation, and processing parameters for injection molding of thermoplastic foam resins with a suitable cell structure that results in specific mechanical and physical properties. With regard to mold design determination and optimization, examples of mold design features that can be investigated and optimized using the apparatus disclosed herein include, but are not limited to, the quantity and location of vents and the design of the gates and runners used to inject polymer into the mold cavity. With regard to formulation optimization, examples of components that can be investigated and optimized with the apparatus disclosed herein include, but are not limited to, the type of molten polymer, the mixture of polymers if more than one polymer is used, the type and amount of blowing agent, and the type and amount of nucleating agent. With regard to processing parameters, examples of parameters that can be investigated and optimized with the apparatus disclosed herein include, but are not limited to, the injection rate and temperature within the barrel and / or mold cavity. It will be understood that the above examples are merely illustrative, and the apparatus and methods disclosed herein can be used to investigate and optimize other aspects of injection molding mold design, formulation, and processing parameters.

[0010] Typically, injection molding a foamed polymer component requires a polymer formulation containing one or more polymers, a blowing agent, and a nucleating agent. This formulation is heated in an injection barrel to a molten state and then injected into a mold cavity using specific processing parameters, such as injection speed, injection pressure, and specific temperatures in the injection barrel and mold cavity. The mold also contains specific features that help fill the mold in the desired manner.

[0011] Proper blending of ingredients is important to achieve a uniform and desirable cell structure, as well as the desired physical and mechanical properties of the resulting molded part. Based on the intended use of the resulting thermoplastic foam, blends can be selected to optimize specific properties, such as physical, mechanical, thermal, insulating, and / or electrical properties. These properties are controlled by the specific cell structure of the thermoplastic foam, which is largely determined by the blend.

[0012] In mold design, the design of gates and runners is an important factor. A proper pressure drop rate is important to form the proper number and distribution of nuclei that result in a uniform cell structure. In the injection molding process, the number of gates, their angle, shape, and diameter, as well as the design and placement of runners, are important to achieve the desired results. Another important feature is the placement of vents in the mold cavity. Before the molten polymer is injected into the mold cavity, the cavity is filled with atmospheric air, which is displaced by the injected polymer. As explained further herein, if the number and placement of vents result in atmospheric air being trapped between the mold cavity wall and the polymer entering the cavity, the flow of the molten polymer can be adversely affected.

[0013] Measuring the pressure throughout the mold cavity during the molding process provides designers with important information for both mold design and processing parameters. As will be explained later in this specification, maintaining a relatively uniform peak pressure throughout the mold cavity during the molding process results in a more uniform and consistent distribution and size of "bubbles" within the molten polymer (i.e., air pockets within the molten polymer that form voids within the polymer matrix as the polymer solidifies), resulting in a consistent physical structure for the solidified polymeric part resulting from the molding process.

[0014] Another important parameter that can be measured and quantified using the apparatus and method disclosed herein is the degree of gas saturation immediately before and during injection of the polymer into the mold cavity during the foaming process. Higher gas solubility leads to higher gas saturation levels and higher melt pressures. Higher gas pressure levels in molten polymers can lead to increased thermodynamic instability and potentially higher pressure drops, resulting in higher expansion rates and lower densities in parts produced during the injection molding process (i.e., lighter parts compared to equivalently sized solid polymer parts). Therefore, measuring gas solubility during the molding process is useful. One advantage of using the apparatus disclosed herein is the ability to control the cell shape of the gas phase in injection-molded parts. Controlling the cell shape of the cell structure can control the mechanical properties of the resulting thermoplastic foam part.

[0015] The apparatus and methods described herein can be used to investigate the formation of foamed resin parts with a "dual-cell" structure. In this disclosure, "dual-cell structure" means that a first portion (e.g., the top or left portion) of the resulting foamed resin part has a first void distribution (i.e., the size and density of voids within the polymer matrix), and a second portion (e.g., the bottom or right portion) of the resulting foamed resin part has a second void distribution. The dual-cell structure of thermoplastic foamed resins, which has two distinct but complementary portions, plays an important role in improving the properties of molded parts. For example, foamed polymers can be molded to enhance impact resistance while maintaining other desirable properties. Specific conditions for forming such dual-cell structures into parts with desirable property combinations can be developed by applying the methods described herein using the apparatus, particularly through strict control over two or more cooling processes incorporated into the mold cavity.

[0016] Figures 1-12 show an exemplary apparatus for determining and optimizing mold design, formulation, and processing parameters for injection molding thermoplastic foams. These figures show a plaque mold with multiple interchangeable mold cavities. The interchangeable mold cavities have multiple pressure sensors for recording pressure and multiple temperature sensors for recording temperature at different locations in the mold cavity. The mold contains two independent water circulation systems that can be used to investigate and develop different cell structures for injection-molded thermoplastic foams, including double-cell structures.

[0017] FIG. 1 illustrates an exemplary plaque mold 10. Plaque mold 10 has an A-side 20 and a B-side 30. A-side 20 includes a first portion 40 of a mold cavity, and B-side 30 includes a second portion 50 of the mold cavity. First portion 40 and second portion 50 combine to form a mold cavity useful for forming polymeric components, including thermoplastic foam components. As will be appreciated, each mold cavity can be selectively removed and replaced with another mold cavity depending on the type of component being formed.

[0018] The apparatus described herein includes the creation of multiple sets of injection molding inserts for producing one solid part and two or more thermoplastic foam parts of various sizes. These injection molding inserts are molded in different pairs of mold cavities to investigate the effect of various parameters on the flow and foaming behavior of various polymer formulations. In the embodiment described herein, a total of five sets of injection molding parts are included, one set for forming the solid part and four sets for forming foam parts of different sizes. While this embodiment illustrates the use of a total of five sets of injection molding inserts, it will be understood that more or less than five sets of injection molding inserts can be used to achieve useful results.

[0019] All mold cavities produce parts with the same upper and lower surface areas, but the resulting part thicknesses vary. In this embodiment, for convenience, the length of the area is designed based on the length required for the largest dogbone-shaped or rectangular specimen for mechanical property testing in accordance with ASTM D638-02a, i.e., 24.60 cm. Figure 2 shows a schematic diagram of such a specimen. The width of the area is set to 18.50 cm, allowing each mold cavity to accommodate at least five specimens. Figures 3 and 4 show schematic diagrams of corresponding pairs of mold cavities used in the method described herein. Figure 3 contains five specimens cut from plaques formed by the mold cavities, designed to produce 3.2 mm thick specimens. Figure 4 contains five specimens cut from plaques formed by the mold cavities, designed to produce 7.0 mm thick specimens. By forming additional plaques, specimens with thicknesses of 14.0 mm and 25.4 mm can be produced. The specimens shown here are useful for testing and comparing the material properties of specimens of various thicknesses, as well as the polymer formulations and processing parameters used to form such specimens. For example, once such specimens are formed, tensile, impact, three-point bend, and other similar tests can be performed to quantify and compare the mechanical properties of the various specimens.

[0020] Below, we describe the mold cavity and plaque mold configurations for producing test specimens of five different thicknesses. Figure 5 shows the mold cavity of a plaque mold that produces a 3.2 mm thick solid test specimen (i.e., no systematic bubbles or void patterns within the polymer matrix). This solid test specimen is used as a control specimen for evaluating subsequent thermoplastic foam test specimens produced using the described method. This configuration features three intra-cavity pressure sensors and an additional pressure sensor located in the relief position. The pressure sensors can be general pressure sensors or specific low- or high-pressure sensors. In one example, the low-pressure sensor can detect pressures from 0 bar (0 psi) to 10 bar (approximately 145 psi), while the high-pressure sensor can detect pressures from 0 bar (0 psi) to 50 bar (approximately 725 psi). In the example shown in Figure 5, the three intra-cavity pressure sensors are high-pressure sensors, and the additional pressure sensor in the relief position is either a high-pressure sensor or a low-pressure sensor, depending on the data you want to collect.

[0021] Figure 6 shows the mold cavity of a plaque mold that produces 3.2 mm thick thermoplastic foam specimens. In one example, this configuration includes three low-pressure sensors within the cavity and either low-pressure or high-pressure sensors in the relief positions. Comparing the 3.2 mm thermoplastic foam specimens to the 3.2 mm solid specimens can provide a better understanding of various parameters.

[0022] Figure 7 shows the mold cavity of a plaque mold used to produce 7.0 mm thick thermoplastic foam specimens. In one example, this configuration includes three low-pressure sensors within the cavity and either low-pressure or high-pressure sensors in the relief positions. Comparing the 7.0 mm thick thermoplastic foam specimens with 3.2 mm thick solid and thermoplastic foam specimens provides a better understanding of various parameters. In particular, the cell structure and weight loss achieved with the thermoplastic foam specimens are compared.

[0023] Figure 8 shows the mold cavity of a plaque mold used to produce 14.0 mm thick thermoplastic foam specimens. In one example, this configuration includes three low-pressure sensors within the cavity and either low-pressure or high-pressure sensors in the relief positions. Comparing the 14.0 mm thick thermoplastic foam specimens with 3.2 mm and 7.0 mm thick thermoplastic foam specimens provides a better understanding of various parameters. In particular, the cell structure and weight loss achieved with the various thermoplastic foam specimens are compared.

[0024] Figure 9 shows the mold cavity of a plaque mold used to produce 25.4 mm thick thermoplastic foam specimens. In one example, this configuration includes three low-pressure sensors within the cavity and one in the relief position. By comparing the 25.4 mm thick thermoplastic foam specimens with those of 3.2 mm, 7.0 mm, and 14.0 mm thickness, a deeper understanding of various parameters can be gained. In particular, the cell structure and weight loss achieved with the various thermoplastic foam specimens are compared. Note that this thickness is the standard thickness for conducting thermal conductivity tests.

[0025] Figures 10A-10D show plaque mold specimens of various thicknesses produced by a plaque mold with multiple replacement mold inserts. Figure 10A shows a plaque mold with a total volume (including cavity, gate, sprue, and runner) of 159.86 cm. 3 Figure 10B shows a 3.2 mm plaque element with a total volume of 337.54 cm 3 Figure 10C shows a 7.0 mm plaque element with a total volume of 663.93 cm 3 Figure 10D shows a 14.0 mm plaque element with a total volume of 1169.67 cm 3 The figure shows a 25.4 mm plaque member.

[0026] Sensors can be strategically placed within the mold cavity to gather data useful in the process, such as the pressure and temperature of the saturated molten polymer. FIG. 11 illustrates four locations for intra-cavity sensors to gather accurate data during the molding process. The sensor labeled 1 is located along the centerline of the mold cavity and is positioned where the polymer begins to flow into the mold cavity. The sensor labeled 2 is located along the centerline of the mold cavity and is positioned at the end of flow through the mold cavity. The sensor labeled 3 is located at one corner of the mold cavity at the end of flow through the mold cavity. The sensor labeled 4 is located in a relief. The sensor placement illustrated in FIG. 11 is merely one example of a sensor placement. It will be understood that any number of sensor placements are useful with the apparatus and methods disclosed herein.

[0027] As previously mentioned, the plaque mold may be equipped with two independent water circulation systems. Figure 12 illustrates such an embodiment. Using two independent water circulation systems can produce test specimens with dual cellular structures. For example, the resulting part can have a first cellular structure throughout a first portion of the specimen and a second, different cellular structure throughout a second portion of the specimen. In one embodiment, the top half of the specimen contains a first cellular structure and the bottom half of the specimen contains a second cellular structure. Such dual cellular structures can be formed by applying two different cooling cycles to the first and second portions of the plaque mold. By varying the cooling cycle in a series of experiments, the apparatus disclosed herein is useful for quickly and efficiently investigating the effects of varying the cooling cycle on the structure of molded test specimens.

[0028] Another useful data point when evaluating mold design, polymer formulation, and process settings is measuring the amount of gas introduced into the molding process and the amount of gas not entrapped in the thermoplastic foam (i.e., outgassing). Gas can be introduced into the molding process in a number of ways. For example, ambient gas can be present in the mold cavity before molding, and gas can be injected into the cavity during the molding process to promote physical foaming. In another example, chemical foaming additives can be used in the polymer formulation to promote gas entrapment. These additives react to generate gas within the injection barrel or mold cavity during part molding, promoting chemical foaming. Evaluating such data points can help determine the solubility of gas in a particular polymer / gas combination. One method for measuring outgassing is to collect all outgassing in a collection tank.

[0029] 13 and 14 show two different perspective views of a plaque mold 100 and collection tank 110, which are connected by a hose 120. To properly collect the vented gases, all exhaust ports from the mold are connected at an exhaust relief at the rear end of the plaque mold 100. The exhaust gases flow from all sides of the plaque mold 100 and are collected at a relief end at the end of the plaque mold. The exhaust relief end is connected by a high-pressure hose 120 to the collection tank 110, which routes all gases, including trapped air, to the collection tank 110, where the collected gases can be measured. An O-ring or other seal can be placed between sides A and B of the mold cavity to prevent gas leakage from the interface between sides A and B of the mold cavity.

[0030] Once fully collected and measured, the volume of the effluent gas can be determined and compared to the total volume of ambient, injected, and / or generated gas and the volume of gas collected from the control specimen. The effluent gas collected and measured during the molding of a solid specimen can be used as a control measurement for comparison with subsequent measurements obtained during the molding of a thermoplastic foam specimen. In one embodiment, the collection tank may have a volume larger than the expected amount of gas to be collected. In such an arrangement, the pressure in the collection tank can be very low during the collection phase so as not to affect the flow of effluent gas into the collection tank. Once the gas is collected, the volume of the collection tank can be reduced to pressurize the collected effluent gas, and a pressure sensor located within the tank can be used to accurately determine the amount of effluent gas. It is convenient to use moles for gas calculations.

[0031] The gas collection system can be configured so that the volume of the collection vessel used to capture the exhaust gas can be adjusted to accommodate mold cavities of various sizes. Larger mold cavities often require more exhaust gas to be collected. Therefore, by allowing the collection vessel to be sized, a gas collection system can be provided that can accommodate multiple mold cavity sizes. Figures 15 and 16 show a schematic of such a gas collection system 200. The gas collection system 200 includes two collection cylinders (210, 220), each of which includes a movable piston (230, 240). The two collection cylinders (210, 220) are connected to a high-pressure hose 250 leading to the plaque mold 100 via a series of pipes or tubes 260. The tubes 260 include valves 270 that can selectively open the fluid path between one or both of the collection cylinders (210, 220) and the hose 250. Additionally, valve 270 can selectively close the fluid path between hose 250 and both collection cylinders (210, 220). Each collection cylinder (210, 220) also has a one-way valve at the interface between tube 260 and the collection cylinder (210, 220) to minimize the possibility of gas leaking from the collection cylinder (210, 220) after it has been collected.

[0032] The volumes of the collection cylinders (210, 220) in selective fluid communication with the plaque mold 100 can be varied in two ways. First, a valve 270 is set to open the fluid path to one or both collection cylinders (210, 220). Second, the volume in each collection cylinder (210, 220) can be varied independently by adjusting the pistons (230, 240). In one example, if the plaque mold is relatively small, the valve 270 can be set to open the fluid path to only one collection cylinder 210, and the corresponding piston 230 can be lowered to reduce the volume of the collection cylinder 210 to fit the mold cavity in the plaque mold 100. If the plaque mold 100 is relatively large, the valve 270 can be set to open the fluid path to both collection cylinders (210, 220), and each piston (230, 240) can be raised to make the volume of the collection cylinders (210, 220) relatively large to fit the mold cavity within the plaque mold 100.

[0033] The pistons (230, 240) are also useful for determining the volume of gas collected in the collection cylinders (210, 220). Once the molding process is complete and all of the exhaust gas has been collected, the pistons (230, 240) can be lowered to compress the collected gas and increase the pressure within the collection cylinders (210, 220). Pressure sensors located within each collection cylinder (210, 220) allow the internal pressure of the collection cylinders (210, 220) to be measured and recorded. These readings, combined with the known volume being measured, can be used to determine the volume of exhaust gas collected at atmospheric pressure. The number of gas molecules (i.e., moles of gas) trapped within the molded part can then be calculated and used to determine the gas solubility of the polymer or polymer blend.

[0034] 17 and 18 schematically illustrate another gas collection system 300. The gas collection system 300 includes three collection cylinders (310, 320, 330), each with a movable piston (340, 350, 360) disposed therein. The collection cylinders (310, 320, 330) are connected to the plaque mold 100 by a tube 370 and a high-pressure hose 380. The tube 370 includes a pair of valves (390, 395) that can be selectively set to open a fluid path between the hose 380 and one or more of the collection cylinders (310, 320, 330). Additionally, the pair of valves (390, 395) can be selectively set to close a fluid path between the hose 380 and the collection cylinders (310, 320, 330). Each collection cylinder (310, 320, 330) also has a one-way valve at the interface between the tube 370 and the collection cylinder (310, 320, 330) to minimize the possibility of gas escaping from the collection cylinder (310, 320, 330) after the gas has been collected.

[0035] The operation of the gas collection system 300 is similar to that described for the gas collection system 200 with two collection cylinders. The gas collection system 300 of FIGS. 17 and 18 provides additional flexibility, allowing the user to select between one and three collection cylinders (310, 320, 330), with the capacity of each collection cylinder (310, 320, 330) independently adjustable. While the example gas collection systems described herein include a single tank, two collection cylinders, and three collection cylinders, it will be understood that any number of collection vessels can be used to collect gas and determine the gas solubility of a polymer. For example, if the volume of gas injected into the mold cavity is significantly increased, it may be necessary to add additional collection cylinders to the collection system 300 shown in FIGS. 17 and 18. The gas collection systems described and illustrated herein are configured to provide the user with the flexibility necessary to adjust for mold cavity size and other variables.

[0036] Experiments were conducted to verify the operation and accuracy of the gas collection system described herein. In one exemplary set of experiments, two polymers were foam injection molded under two different conditions. In the first set, a GPPS / HIPS blend was used under processing conditions expected to result in good gas solubility, while in the second set, polypropylene (PP) was used under processing conditions expected to result in poor gas solubility. In PP foam injection molding experiments, PP foaming is highly temperature-sensitive, and the processing temperature range within which PP foams well during injection molding is known to be narrow. Therefore, processing temperatures outside the narrow temperature range for foaming were used in the experiments, and the resulting molded specimens were expected to have poor gas solubility. Because both GPPS / HIPS blends generally have good gas solubility, processing parameters were selected to result in good foaming of the polymer blend, and the resulting molded specimens were expected to have good gas solubility. After conducting these complementary experiments, the amount of exhaust gas collected by the gas collection system was quantified and compared. The results showed that the gas collection system collected five times more moles of exhaust gas from PP foam specimens than from GPPS / HIPS blend injection-molded foam specimens. When the foam specimens had poor gas solubility, the amount of exhaust gas collected was relatively large, whereas when the foam specimens had good gas solubility, the amount of exhaust gas collected was relatively small. Therefore, the results of complementary experiments were as expected. The experiments described here confirm the operation of the gas collection system. Furthermore, experiments were conducted using PP and processing parameters within a narrow temperature range for PP foaming. The exhaust gas collected from these molded specimens was significantly less than that collected from injection-molded PP specimens outside the narrow temperature range for PP foaming. These additional experiments further confirmed the operation of the gas collection system.

[0037] The exhaust gases collected by the gas collection system can be quantified in a variety of ways. However, in one embodiment, a relative measure of gas solubility may be developed. As will be appreciated, while calculating the exact amount of exhaust gases in an injection-molded specimen is useful, it is paramount for those selecting polymers and process parameters and designing molds for foam injection molding to be able to efficiently and effectively compare multiple sets of polymers, process parameters, and mold designs to identify the most desirable one. Using a relative measure, this goal can be achieved without requiring precise calculation of the specific moles of exhaust gases in each injection-molded specimen. Using such a relative measure, exhaust gases and other factors not collected during an experiment can also be normalized. Such a relative measure assigns a relative value on a predetermined scale to the polymer (or polymer blend), process conditions, and mold design parameters used to mold each specimen. Using such a value, comparisons can be quickly made with other experiments using different polymers, process conditions, and mold design parameters to determine which produce superior gas solubility results. This provides an efficient method for quickly evaluating various conditions.

[0038] In this way, collecting and / or calculating gas emissions is useful for optimizing various factors in injection molding, such as the gas solubility of various polymers and polymer blends, the effect of blowing and nucleating agents on gas solubility, the effect of injection speed on gas solubility, the effect of temperature on gas solubility, and the effect of mold design parameters on gas solubility.

[0039] The above disclosure generally describes the arrangement of the apparatus and the use of such apparatus in investigating mold designs, polymer formulations, and processing parameters for forming polymers, particularly foamed polymers. The following disclosure provides specific examples of how the apparatus can be used to investigate and optimize mold designs, polymer formulations, and processing parameters for formed polymers.

[0040] The following example details the use of the plaque mold system described herein to investigate the chemical composition of different polymers and polymer blends, specifically to evaluate their foaming behavior. Two different polymers were used in this example: general-purpose polystyrene (GPPS) and high-impact polystyrene (HIPS). Four separate experiments were conducted on different blends of the two polymers: 100% GPPS, 100% HIPS, a 70% / 30% GPPS / HIPS blend, and a 50% / 50% GPPS / HIPS blend. While GPPS is a rigid polymer, HIPS is a styrene-based polymer containing butadiene rubber chains, which enhance the toughness of the polymer. These polymers are compatible with each other and can be mixed in different ratios. However, because chain mobility and melt strength vary between polymers, each polymer exhibits different foaming behavior when processed individually with the same molding parameters. All formulations used here were processed under the same processing conditions and with the same amount of blowing agent concentration. Pressure sensors were placed at three different locations within the mold cavity, and pressure was measured at these three different locations. The first location is referred to as "Start of Fill" ("SOF") and is identified in FIG. 11 as sensor number 1. The second location is referred to as "End of Fill Center" ("EOF Center") and is identified in FIG. 11 as sensor number 2. The third location is referred to as "End of Fill Corner" ("EOF Corner") and is identified in FIG. 11 as sensor number 3.

[0041] Figure 19 shows a comparison of pressure curves recorded by an SOF sensor in a 14 mm mold cavity for four different experiments (100% GPPS, a 70% / 30% GPPS / HIPS blend, a 50% / 50% GPPS / HIPS blend, and a 100% HIPS blend). The curves represent the average values ​​of 7–10 different runs for each of the four experiments. The graphs in Figure 19 show that as the HIPS ratio increases, the pressure peak for the saturated melt decreases. As the peak pressure increases, more gas molecules are generally trapped within the polymer during the foam molding process. These graphs reveal that GPPS can retain more gas molecules during the foam molding process compared to HIPS. This is due to the higher melt strength of GPPS compared to HIPS. This means that a greater percentage of gas molecules generated by the blowing agent escapes in the saturated HIPS compared to GPPS. As a result, the potential for bubble growth is lower in parts made from HIPS compared to parts made from GPPS under the same processing conditions and blowing agent concentration. The weight loss of the parts formed during these experiments is consistent with the conclusions drawn from the pressure curves in Figure 19. The weight loss of the parts was 39% for GPPS and 35% for HIPS. Therefore, GPPS, with its higher pressure curve peak, exhibited better foaming behavior and greater weight loss than HIPS. The weight loss for the GPPS / HIPS mixture was approximately 37%, with the pressure curve peak falling between GPPS and HIPS, as expected. This experiment demonstrates how the device can be used to optimize formulations for foam injection molding of mixed polymers by quickly and effectively investigating the properties of various polymer blends.

[0042] Figure 20 shows a comparison of the pressure curves of the same saturated polymer blends as in Figure 19, recorded by an EOF center sensor in a 14 mm cavity. Similar to SOF, increasing the HIPS ratio reduces the saturated melt pressure peak at the EOF center. Another interesting observation relates to the change in pressure peak versus fill time for the various blends. The HIPS pressure curve is shifted toward shorter fill times compared to GPPS. In other words, saturated HIPS approaches the edge of the fill center significantly faster than GPPS. As shown by the curves for 100% GPPS, the 70% / 30% GPPS / HIPS blend, the 50% / 50% GPPS / HIPS blend, and 100% HIPS, the peak in the pressure curve occurs earliest for 100% HIPS, later for the blends, and finally for 100% GPPS. The pressure curves show that the GPPS peak occurs at approximately 12 seconds, while the HIPS peak occurs at approximately 6 seconds. Thus, HIPS-based saturated melts reach the EOF approximately twice as fast as GPPS. Such information is extremely useful for mold designers and those selecting formulation and processing parameters.

[0043] Figure 21 shows a comparison of pressure curves recorded by the EOF corner sensor for the same saturated polymer mixture in a 14 mm cavity. Similar to the pressure readings at the SOF and EOF center, the pressure peak for the saturated melt at the EOF corner also decreases with increasing HIPS ratio. Furthermore, HIPS exhibits double-foaming behavior at the EOF corner. As shown in Figure 21, in some runs for the saturated HIPS melt, the pressure peak occurs at approximately 12 seconds, while in other runs, the pressure peak occurs at approximately 7 seconds. In other words, the saturated HIPS melt in some runs approaches the EOF corner sensor significantly faster than in other runs. This behavior is observed randomly across different injection runs.

[0044] This behavior suggests that the apparatus disclosed herein can be used to determine whether a particular polymer or polymer mixture generates a "developed" or "random" flow pattern when injected into a mold cavity. In this disclosure, a "developed" flow pattern means that as the polymer is injected into the cavity, it forms a "U-shaped flow front" from the injection point to the farthest wall of the mold cavity, filling the cavity symmetrically. Figures 22A-22D show a schematic representation of the progression of such a developed flow, with Figure 22A showing the flow front early in the injection molding process and Figure 22D showing the flow front at the end of the molding process. The flow front first reaches the center of the farthest wall of the mold cavity, and then the corners are simultaneously filled. In this disclosure, a "random" flow means that the flow does not follow a symmetrical or regular path. The polymer fills the mold cavity with the flow front reaching the farthest wall of the mold cavity in random locations. This means that with each injection, the flow front may unpredictably reach the center of the far wall first, the right corner first, or the left corner first.As described in the experiments below, the use of EOF center and corner sensors can determine whether a polymer or polymer blend is in developed or random flow under a variety of conditions.

[0045] To understand the flow behavior of a polymer or polymer blend, short-shot analyses were performed using foamed resin injection-molded parts based on two different systems: GPPS and HIPS. Such analyses demonstrate the practical advantages of the plaque mold system described herein. Figure 23 shows a photograph and accompanying schematic model of the flow behavior in a short-shot analysis of a 14 mm GPPS part. As shown, the saturated GPPS melt exhibits a uniform and symmetric velocity flow profile with a U-shaped flow from the SOF to the EOF until the mold cavity is filled. After performing the short-shot analysis, pressure readings versus time from the EOF center sensor and EOF corner sensors were used to verify the results. As can be seen, the use of such sensors eliminates the need for multiple short-shot analyses. The pressure readings from the EOF center sensor and EOF corner sensors can be used to determine whether the polymer flow is developed. Essentially, if the EOF center sensor detects continuous polymer flow at the EOF center sensor before the polymer flow reaches the EOF corner sensor, the flow is developed. If the EOF corner sensors detect polymer flow periodically before the EOF center sensor detects it, the flow is random. While the method described uses one EOF corner sensor, it is understood that two EOF corner sensors can be placed at opposite corners to gather additional data, such as determining whether the polymer flow arrives at each corner at approximately the same time or at significantly different times.

[0046] Figure 24 shows a photograph and accompanying schematic model of the flow behavior in a short-shot analysis of a 14 mm HIPS component during the early stages of the foam injection process. As shown, the polymer flow is random, approaching the mold cavity corners differently with each injection. As mentioned above regarding the use of pressure readings to determine developed flow, pressure readings from the EOF corner sensor can be used to determine whether the flow is random without requiring multiple short-shot tests. For example, if the time it takes for the EOF corner sensor to detect polymer flow at that location across multiple injection molding experiments is inconsistent, the polymer flow is random. More specifically, if the data for the time it takes for the EOF corner sensor to detect polymer flow at that location across multiple experiments fall into two statistical groups, the polymer flow is random. As shown in Figure 24, comparing the lower left and lower right diagrams, in the case of random flow, the time data required for the polymer to reach the EOF corner sensor is significantly shorter at a certain rate (lower right diagram), while the time data required for the polymer to reach the EOF corner sensor is significantly longer at a certain rate (lower left diagram). In the schematic example shown in Figure 24, one EOF corner sensor is used. However, in other embodiments, two EOF corner sensors or an EOF center sensor can be used to increase the amount of data collected for analysis.

[0047] Figures 25-27 show comparisons of the temperature curves for the same saturated polymer blends shown in Figures 19-21 at the SOF sensor, EOF center sensor, and EOF corner sensor, respectively. The graphs show that as the HIPS ratio increases, the temperature peak of the saturated melt decreases at all three locations. This means that more gas molecules are escaping from the bulk of the saturated HIPS melt, resulting in more heat being removed from the melt and a decrease in temperature. Therefore, this finding supports the results of the pressure curves, indicating that under the same processing conditions and concentrations of blowing agent / gas molecules, the bubble growth potential of the HIPS blend is lower than that of the GPPS blend. Furthermore, as shown in Figure 26, the HIPS-based saturated melt approaches the EOF center position faster than the other blends. Figure 27 shows the temperature curves of different blends at the EOF corner, as well as the double foaming behavior and random packing behavior of the 100% HIPS blend.

[0048] Figure 28 is a series of photographs showing foamed resin parts injected with different formulations. The 100% GPPS part (leftmost part) shows uniform and symmetrical flow paths. As the HIPS content increases from left to right, random flow paths become more pronounced, with the 100% HIPS part (rightmost part) showing the most random flow.

[0049] In the above example, the benefits of various blends of GPPS and HIPS are evaluated. GPPS provides a good surface finish in the final product, but its brittle nature can make it undesirable. HIPS offers toughness and high impact resistance, but a poor surface finish. Blending GPPS and HIPS maximizes the properties of both polymers. However, optimizing the exact blend ratio and processing parameters typically requires extensive trial and error. Using the plaque mold system described herein, various properties of two different polymers and polymer blends can be rapidly evaluated. For example, the flow of the polymer and polymer blend within the mold cavity can be evaluated as developed or random. Pressure and temperature curves can be used to tailor the formulation to control the packing behavior of the polymer blend in a specific mold design. Using the plaque mold system, formulations capable of achieving targeted weight loss can be further developed. It is understood that designing a formulation with an optimal blowing agent concentration optimizes the gas molecule content, improving foaming behavior. This objective can be achieved using the plaque mold system. The system evaluates the compatibility of different gas molecules within a polymer or polymer blend to achieve reduced emissions and improved expansion rates, resulting in significant weight savings.

[0050] The following example describes how to optimize processing conditions, particularly injection speed. Injection speed affects the cell structure of foamed polymers and can therefore affect the mechanical properties of the final molded part. Therefore, understanding the effects of injection speed is important in designing an optimized molding process. The method described here uses data collected by three pressure sensors: a pressure sensor at the SOF, a pressure sensor at the center of the EOF, and a pressure sensor at the corner of the EOF. In a specific experiment, two different grades of nylon 66 were used to determine the optimal injection speed. The first grade of nylon 66 had a relatively high viscosity and a relatively low melt flow rate, referred to here as N66-HV. The second grade of nylon 66 had a relatively low viscosity and a relatively high melt flow rate, referred to here as N66-LV. For each grade of nylon 66, a 14 mm mold cavity was used, and an injection speed of 5 cubic inches (approximately 81.9 cm3) was used. 3 ) / sec, 10 cubic inches (approximately 163.8 cm 3 ) / second and 20 cubic inches (approximately 327.7 cm 3 Test parts were molded at three injection rates: 1 / sec, 2 / sec, 3 / sec, 4 / sec, 5 / sec, 6 / sec, 7 / sec, 8 / sec, 9 / sec, 10 / sec, 11 / sec, 12 / sec, 13 / sec, 14 / sec, 15 / sec, 16 / sec, 17 / sec, 18 / sec, 19 / sec, 20 / sec, 21 / sec,

[0051] For N66-LV, Figure 29 shows the injection speed of 5 cubic inches (approximately 81.9 cm 3 Figure 30 is a graph of pressure versus time for three sensors at an injection velocity of 10 cubic inches (approximately 163.8 cm) / second. 3 Figure 31 is a graph of pressure versus time for three sensors at an injection velocity of 20 cubic inches (approximately 327.7 cm3) / second. 3 29-31 are graphs of pressure versus time for the three sensors at an injection speed of 5 cubic inches (approximately 81.9 cm³). To obtain a uniform cell structure, it is desirable for the peak pressure readings of the SOF and EOF sensors to be approximately equal. If the peak pressures are approximately equal throughout the mold cavity, it is believed that cell initiation and growth will proceed uniformly throughout the molded specimen. As shown in Figures 29-31, at an injection speed of 5 cubic inches (approximately 81.9 cm³), 3) / sec, the peak pressure of the EOF sensor is significantly higher than that of the SOF sensor, and the injection velocity is 20 cubic inches (approximately 327.7 cm 3 ) / sec, the peak pressure of the EOF sensor is significantly lower than that of the SOF sensor. This pressure difference can lead to a non-uniform bubble structure. However, if the injection velocity is 10 cubic inches (approximately 163.8 cm 3 ) / sec results in a uniform peak pressure at the EOF and SOF sensors. Therefore, from this test, it was determined that the injection velocity should be set to 10 cubic inches (approximately 163.8 cm 3 ) / sec., the uniformity of the cellar structure of foamed parts injection-molded using N66-LV is optimized. Morphological analysis was performed by cutting test specimens and observing the internal cell structure. As a result, it was found that an injection speed of 10 cubic inches (approximately 163.8 cm 3 ) / sec was confirmed to optimize the uniformity of the cellar structure of N66-LV.

[0052] For N66-LV, Figure 32 shows the injection speed of 5 cubic inches (approximately 81.9 cm 3 ) / sec. Figure 33 shows the pressure versus time for the three sensors at an injection velocity of 10 cubic inches (approximately 163.8 cm). 3 ) / sec. Figure 34 shows the pressure versus time graph for the three sensors at an injection velocity of 20 cubic inches (approximately 327.7 cm). 3 ) / sec. In the N66-HV experiment, injection noise (shown by the dashed circle) was observed in the SOF sensor early in the injection cycle. At an injection speed of 5 cubic inches (approximately 81.9 cm 3 ) / sec, the peak pressure of the SOF sensor was determined to be the infection point of the downward curve after the initial injection noise. As shown in Figures 32 to 34, at an injection velocity of 10 cubic inches (approximately 163.8 cm 3 ) / second and 20 cubic inches (approximately 327.7 cm 3 ) / sec, the peak pressure of the SOF sensor is significantly higher than that of the EOF sensor. However, at an injection velocity of 5 cubic inches (approximately 81.9 cm 3) / sec, the peak pressures of the EOF sensor and the SOF sensor match. Therefore, this test was conducted at an injection speed of 5 cubic inches (approximately 81.9 cm 3 ) / sec., the uniformity of the cell structure of foamed parts injection-molded using N66-HV is optimized. Morphological analysis was performed by cutting the test specimens and observing the internal cell structure. As a result, it was found that an injection speed of 5 cubic inches (approximately 81.9 cm3) / sec. 3 ) / sec was confirmed to optimize the uniformity of the cellar structure of N66-HV.

[0053] The pressure measurements collected by the SOF and EOF sensors in the above experiments provide information on the uniformity of the cell structure as well as the size of the voids where no polymer matrix is ​​present. Lower pressures allow larger cell growth during the molding process, resulting in larger voids. In embodiments of the methods used in conjunction with the apparatus described herein, multiple tests can be performed to identify, for example, (i) process parameters that result in low, uniform peak pressures throughout the mold cavity, promoting a uniform cell structure with large voids; (ii) process parameters that result in high, uniform peak pressures throughout the mold cavity, promoting a uniform cell structure with small voids; or (iii) process conditions that provide a pressure difference between the SOF and EOF to promote a gradient cell structure throughout the resulting molded part.

[0054] The following example describes how to optimize the concentration of components in a formulation, specifically the blowing agent. By optimizing the blowing agent concentration in a formulation used for foam injection molding, improved cell structure uniformity, reduced density, reduced shrinkage, and reduced weld seams can be achieved in the resulting molded part. In this experiment, polyvinyl chloride (PVC) was used as the base polymer and mixed with different concentrations of blowing agent: 1.0%, 1.25%, and 1.5%. The blowing agent was used to accelerate the foaming process. A 14 mm mold cavity was used. Pressure readings were measured and recorded at three locations: the SOF, the center of the EOF, and the corner of the EOF. The data collected from the pressure sensor was graphed versus time, as shown in Figure 35. The SOF sensor detected injection noise at the beginning of the cycle (shown by the dashed circle), and the inflection point of the downward curve after the noise was the peak pressure of the SOF sensor. For a formulation with a 1.5% blowing agent concentration, the peak pressure at the EOF was closest to the peak pressure at the SOF sensor. Therefore, among these three foaming agent concentrations, the 1.5% concentration produced the most uniform cell structure, a result confirmed by morphological analysis.

[0055] Additional components can be used in the apparatus described herein to optimize mold design. For example, inserts can be used to selectively change the location and size of vents throughout the mold. Venting is important in injection molding because the atmosphere within the mold cavity must be considered when designing the mold cavity and molding process. Venting is a common method for controlling and venting atmospheric air during the molding process. Conventional vent placements often force the atmosphere within the mold cavity out the back of the mold (such as the EOF corner locations described herein) during the injection molding process. If not properly vented, this atmosphere can collect in the EOF corner, potentially preventing the mold cavity from filling completely or causing unnecessary pressure buildup in one portion of the mold cavity.

[0056] To investigate solutions to these problems, multiple exhaust inserts with different numbers of exhaust ports can be fabricated. These exhaust inserts can be interchangeably incorporated into the mold cavity and used in multiple experiments to investigate the effect of different degrees of exhaust on the molding process. In one experiment, three individual exhaust inserts with different numbers of exhaust ports were used and adjusted to be positioned at both EOF corner locations. Multiple parts were molded using the three exhaust inserts, and pressure measurements were collected and recorded at the two EOF corner locations and the EOF center location throughout the molding process. By analyzing the pressure data at various locations during the molding process, the effects of atmospheric air and its venting can be determined. The results of this determination can be used to optimize the exhaust ports in the final mold cavity for mass production of parts.

[0057] In another example, multiple inserts for the injection gate and runner may be fabricated to explore the effects of various gate and runner configurations. For example, single-gate and double-gate inserts may be fabricated. In another example, gates of different diameters may be fabricated. In yet another example, gates positioned at different angles relative to the mold cavity may be fabricated. Similarly, for runners, the number of runners, runner diameter, runner position, and runner angle may be varied to create as many inserts as necessary to fully test their effect on the molding process. As with the above discussion, multiple experiments may be conducted during the molding process, and measurements such as temperature and pressure may be collected and recorded. Such data can be used to optimize gate and runner styles for a particular mold cavity and molding process.

[0058] The above descriptions of examples have been presented for purposes of explanation and illustration. They are not exhaustive and are not limited to the forms described. Numerous variations are possible based on the above description. Some of these variations have been described above, and others will be apparent to those skilled in the art. The above examples have been selected and described in order to best illustrate the principles of various examples suited to the particular applications contemplated. Of course, the scope of the present invention is not limited to the examples described herein, and those skilled in the art will be able to adapt it to any number of applications and equivalent arrangements.

Claims

1. 1. A plaque mold assembly for forming a polymeric member, comprising: a plurality of interchangeable mold cavities each having at least one sensor; one of the plurality of mold cavities is selectively used to form a polymeric member; A plaque mold assembly, wherein the at least one sensor in the mold cavity used to form the polymeric member is positioned to measure an environmental parameter during formation of the polymeric member.

2. The plurality of interchangeable molds are a first mold cavity configured to form at least one generally solid polymeric member; a second mold cavity configured to form at least one 3.2 mm thermoplastic foam member; a third mold cavity configured to form at least one 7.0 mm thermoplastic foam member; a fourth mold cavity positioned to form at least one 14.0 mm thermoplastic foam member; a fifth mold cavity configured to form at least one 25.4 mm thermoplastic foam member.

3. 3. The plaque molding assembly of claim 2, wherein the properties of the solid polymer member formed in the first mold cavity are comparable to the properties of one or more thermoplastic foam members formed in at least one of the second, third, fourth, and fifth mold cavities to analyze variables.

4. The plaque mold assembly of claim 3 , wherein the variables include mold design, polymer formulation, and processing parameters.

5. The plaque mold assembly of claim 3 , wherein the variables include mechanical properties including tensile strength, impact resistance, and flexural strength.

6. a first water circulation system; The plaque mold assembly of claim 1 , further comprising a second water circulation system independent of the first water circulation system.

7. 7. The plaque mold assembly of claim 6, wherein the first and second water circulation systems are independently controllable such that the formed polymeric member has different mechanical properties across different portions of the polymeric member.

8. an exhaust system positioned to provide a path for gas not entrapped in the polymeric member during formation to escape from the mold cavity; a collection system for containing gas not entrapped in the polymeric member during formation; The plaque mold assembly of claim 1 , further comprising a hose connecting the exhaust system and the collection system.

9. The plaque mold assembly of claim 8 , wherein the volume of gas collected in the collection system during the forming process can be used to determine the gas solubility of the polymeric member.

10. 9. The plaque mold assembly of claim 8, wherein the collection system includes two cylinders in selective fluid communication with the exhaust system to contain gas not entrapped in the polymeric member during formation.

11. 11. The plaque mold assembly of claim 10, wherein each cylinder has an adjustable piston that can vary the volume of the cylinder.

12. 12. The plaque mold system of claim 11, wherein each cylinder includes a pressure sensor for measuring the internal pressure of the cylinder.

13. 12. The plaque mold system of claim 11, wherein each cylinder has a temperature sensor for measuring the temperature of the cylinder.

14. The plaque mold assembly of claim 1 , wherein the at least one sensor is positioned to measure the environmental parameter at regular intervals during formation of the polymeric member.

15. The plaque mold assembly of claim 1 , wherein the at least one sensor is a plurality of sensors distributed throughout the mold cavity.

16. The plaque mold assembly of claim 15 , wherein at least one of the plurality of sensors is positioned to measure pressure or temperature.

17. 1. A plaque mold assembly for forming a polymeric part to study the behavior of the polymer during a molding process, comprising: a plurality of interchangeable mold cavities; a plurality of sensors disposed within each of the plurality of interchangeable mold cavities; a first mold cavity is selectively used to form one or more polymeric members; The plaque mold assembly, wherein the plurality of sensors includes a sensor disposed within the first mold cavity.

18. 18. The plaque mold assembly of claim 17, wherein the sensor measures and records temperature measurements throughout the molding process, and the temperature measurements are used to plot a graph of temperature versus time during the molding process.

19. 18. The plaque mold assembly of claim 17, wherein the sensor measures and records pressure throughout the molding process, and the pressure measurements are used to plot a graph of temperature versus time during the molding process.

20. 18. The plaque mold assembly of claim 17, wherein measurements obtained by the sensor are used to evaluate flow behavior of a polymer used to form the one or more polymer members, processing parameters used to form the one or more polymer members, or mold design features of the mold cavity used to form the one or more polymer members.

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