Polymer composite material and preparation method therefor

Abstract

The present application relates to a polymer composite material and a preparation method therefor. The polymer composite material comprises polylactic acid and polybutylene terephthalate, wherein the polybutylene terephthalate is 0.1%-0.5% of the total mass.

Description

A polymer composite material and its preparation method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 12, 2023, with application number 202311721396.4 and invention name “A polymer composite material and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of composite material preparation, and in particular to a polymer composite material and a preparation method thereof. Background Art

[0003] Polylactic acid (PLA) is a commonly used biodegradable plastic with enormous potential for applications in packaging, clothing, consumer electronics, and medical applications. However, pure PLA exhibits poor mechanical properties, particularly high brittleness and low impact strength. Therefore, to improve the mechanical properties of PLA, common modification methods include copolymerization, additives, and blending.

[0004] In traditional technology, the method of adding fillers such as natural fibers, talc powder, and chitosan to the PLA matrix is ​​often used to improve the mechanical properties of PLA. However, the physical properties of these fillers are significantly different from those of the matrix, resulting in the fillers not being fully dispersed and the improvement of mechanical properties being limited. Summary of the Invention

[0005] The purpose of this application is to solve at least one of the above-mentioned technical defects, especially the technical defect that when using composite modification methods in traditional technologies to improve the mechanical properties of PLA materials, there is a problem that the physical properties of the filler and the matrix are quite different, resulting in the filler not being able to be completely dispersed, and thus the mechanical properties of the PLA composite material prepared by using the above-mentioned filler are limited.

[0006] The present application provides a polymer composite material, which comprises polylactic acid and polybutylene terephthalate;

[0007] Wherein, the polybutylene terephthalate accounts for 0.1%-0.5% of the total mass proportion.

[0008] Optionally, the composite material further comprises polyethylene glycol;

[0009] The polyethylene glycol accounts for 1%-2% of the total mass ratio.

[0010] Optionally, the polylactic acid is L-polylactic acid;

[0011] The melt flow rate of the L-polylactic acid is 3-5 g / 10 min.

[0012] Optionally, the density of the polybutylene terephthalate is 1.4 g / cm 3 , length 3mm, diameter 30μm.

[0013] The present application also provides a method for preparing the polymer composite material as described in any one of the above embodiments, the method comprising:

[0014] Placing polylactic acid and polybutylene terephthalate in a vacuum environment for drying, wherein the polybutylene terephthalate accounts for 0.1%-0.5% of the total mass ratio;

[0015] The dried polylactic acid and polybutylene terephthalate are placed under successively increasing heating temperatures and mixed to obtain composite material particles, wherein the heating temperature is a minimum of 155-165° C. and a maximum of 190-200° C.;

[0016] placing the composite material particles in a vacuum environment for drying;

[0017] The dried composite material particles are injection molded to obtain a polymer composite material.

[0018] Optionally, the step of drying the polylactic acid and polybutylene terephthalate under a vacuum environment comprises:

[0019] The polylactic acid and polybutylene terephthalate were placed in a vacuum drying oven and dried under vacuum conditions at 100° C. for 2 hours.

[0020] Optionally, the step of mixing the dried polylactic acid and polybutylene terephthalate at successively increasing heating temperatures to obtain composite material particles comprises:

[0021] The dried polylactic acid and polybutylene terephthalate are added into a twin-screw mixing granulator for mixing to obtain composite material particles;

[0022] Wherein, the heating temperature of each heating zone of the twin-screw mixing granulator increases successively.

[0023] Optionally, the rotation speed of the twin-screw mixing granulator is 30 rpm.

[0024] Optionally, the twin-screw mixing granulator includes a conveying section, a melting section, a mixing section, a venting section, and a homogenizing section;

[0025] Wherein, the heating temperature of the conveying section is 160°C;

[0026] The heating temperature of the melting section is 170°C;

[0027] The heating temperature of the mixing section is 180°C;

[0028] The heating temperature of the exhaust section is 190°C;

[0029] The heating temperature of the homogenization section is 195°C.

[0030] Optionally, the placing the composite material particles under a vacuum environment for drying comprises:

[0031] The composite material particles were placed in a vacuum drying oven and dried under vacuum conditions at 100° C. for 2 hours.

[0032] Optionally, the step of injection molding the dried composite material particles to obtain the polymer composite material comprises:

[0033] The dried composite material particles are added into a horizontal injection molding machine for injection molding to obtain a polymer composite material.

[0034] Optionally, the injection temperatures of the barrel sections of the horizontal injection molding machine are 170°C, 180°C, 190°C, and 195°C, respectively;

[0035] The injection speed of the horizontal injection molding machine is 40 mm / s.

[0036] Optionally, the method further includes:

[0037] When polylactic acid and polybutylene terephthalate are placed in a vacuum environment for drying, polyethylene glycol with a mass fraction of 1%-2% is added and dried and mixed together.

[0038] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0039] The present application provides a polymer composite material and a preparation method thereof. The composite material may include polylactic acid and polybutylene terephthalate. Moreover, since polylactic acid and polybutylene terephthalate are both aliphatic polyester compounds and have similarities in density and polar group properties, the composite material formed by compounding these two substances has better compatibility than traditional natural fiber fillers and inorganic powder fillers, thereby effectively improving the mechanical properties of the PLA composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0041] FIG1 is a schematic flow chart of a method for preparing a polymer composite material provided in an embodiment of the present application;

[0042] FIG2 is a graph of elongation at break for different reinforcing fiber volume fractions provided in an embodiment of the present application;

[0043] FIG3 is a graph showing the impact strength of different reinforcing fiber volume fractions provided in an embodiment of the present application. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0045] Currently, common modification methods for improving the mechanical properties of PLA materials include copolymerization, additives, and blending. Traditionally, fillers such as natural fibers, talc, and chitosan have been added to the PLA matrix to enhance its mechanical properties. However, these fillers exhibit significant differences in physical properties from the matrix, resulting in incomplete dispersion of the fillers and limited improvements in mechanical properties.

[0046] Based on this, this application proposes the following technical solutions, as shown below:

[0047] In one embodiment, the present application provides a polymer composite material comprising polylactic acid and polybutylene terephthalate.

[0048] Wherein, the polybutylene terephthalate accounts for 0.1%-0.5% of the total mass proportion.

[0049] In this embodiment, when modifying the polylactic acid (PLA) polymer material to improve its mechanical properties, the present application may consider compounding polybutylene terephthalate (PBT), which is also an aliphatic polyester compound, with PLA. Since these two substances are similar in density and polar group characteristics, the composite material obtained by compounding the two has high compatibility, thereby avoiding the problem of filler inability to be completely dispersed when using traditional natural fiber fillers and inorganic powder fillers for compounding; and, since PBT has the characteristics of high heat resistance, inability to resist strong acids and strong alkalis, resistance to organic solvents, flammability, and decomposition at high temperatures, compounding it with PLA can effectively improve the mechanical properties of the PLA composite material.

[0050] In a specific implementation, when compounding PBT and PLA, the mass fraction of PLA can be controlled to be 0.1%-0.5% of the total mass ratio. This can not only obtain a composite material with higher mechanical properties, but also avoid using too much PLA, which may lead to obvious defects such as delamination and porosity in the composite material.

[0051] Furthermore, when compounding PBT and PLA, the present application can select PBT and PLA of corresponding specifications and configurations according to the application field and product requirements. The specific selection can be made according to the actual situation and is not limited here.

[0052] In addition, the PBT fibers of the present application can be virgin PBT fibers or recycled PBT fibers. Virgin PBT fibers refer to unused PBT fibers, and recycled PBT fibers refer to PBT fibers that have been recycled after use. To improve the environmental properties of the material, the present application can replace virgin PBT fibers with recycled PBT fibers of the same specifications. This can improve the mechanical properties and environmental properties of the composite material while also reducing production costs.

[0053] In one embodiment, the composite material may further include polyethylene glycol.

[0054] The polyethylene glycol accounts for 1%-2% of the total mass ratio.

[0055] In this embodiment, when PLA is modified by composite modification, a certain mass fraction of polyethylene glycol may be added. This can improve the fluidity and dispersion effect of PLA and PBT during composite modification and increase the production yield of injection molded parts.

[0056] Among them, when performing composite modification of PLA and PBT, the present application can add polyethylene glycol (PEG) accounting for 1%-2% of the total mass. This can not only improve the compatibility of PLA and PBT and enable the two to be effectively mixed, but also increase the production yield of injection molded parts, improve production efficiency and production quality.

[0057] In one embodiment, the polylactic acid is poly (L-lactic acid).

[0058] The melt flow rate of the L-polylactic acid is 3-5 g / 10 min.

[0059] In this embodiment, since there is an asymmetric carbon atom in the lactic acid molecule, it has optical activity. Therefore, polylactic acid is also divided into dextrorotatory polylactic acid (PDLA), levorotatory polylactic acid (PLLA), racemic polylactic acid (PDLLA), and optically inactive polylactic acid (Meso-PLA).

[0060] Among them, the present application can choose left-handed polylactic acid (PLLA) and PBT for compounding. The characteristics of this L-polylactic acid are non-toxic, non-irritating, biodegradable and absorbable, high strength, good plasticity, and easy processing and molding; its degradation cycle is generally 2 to 12 months, and the degradation cycle of PLLA can be changed by adding different modifiers. In addition, PLLA undergoes enzymatic decomposition in the body, ultimately forming carbon dioxide and water, and therefore has good biocompatibility. The present application uses PLLA to compound with PBT to further improve the compatibility of the composite material.

[0061] In addition, to improve the quality of the composite material, the present application may select, in addition to PLLA, a PLLA with a melt flow rate of 3-5 g / 10 min. The melt flow rate herein also refers to the melt index (MI), specifically the number of grams of molten resin flowing out through a standard capillary tube within a certain time (generally 10 minutes) under certain temperature and pressure in a standardized melt indexer, expressed in g / 10 min. Melt flow rate is an important reference for selecting plastic processing materials and grades. When PLLA with a melt flow rate of 3-5 g / 10 min is selected as the PLA masterbatch, it can better meet the requirements of the processing technology, thereby improving the reliability and quality of the product molding.

[0062] In one embodiment, the density of the polybutylene terephthalate is 1.4 g / cm 3 , length 3mm, diameter 30μm.

[0063] In this embodiment, when PLA and PBT are compounded, the present application can use a density of 1.4g / cm 3 , PBT with a length of 3 mm and a diameter of 30 μm, which can not only improve the compatibility of the composite material, but also improve the quality of the composite material.

[0064] In one embodiment, as shown in FIG1 , FIG1 is a schematic flow chart of a method for preparing a polymer composite material provided in an embodiment of the present application; the present application also provides a method for preparing a polymer composite material as described in any one of the above embodiments, the method may include:

[0065] S110: drying the polylactic acid and polybutylene terephthalate in a vacuum environment, wherein the polybutylene terephthalate accounts for 0.1% to 0.5% of the total mass.

[0066] S120: mixing the dried polylactic acid and polybutylene terephthalate at successively increasing heating temperatures to obtain composite material particles, wherein the heating temperature is as low as 155-165° C. and as high as 190-200° C.

[0067] S130: placing the composite material particles in a vacuum environment for drying.

[0068] S140: injection molding the dried composite material particles to obtain a polymer composite material.

[0069] In this embodiment, when preparing a polymer composite material, the present application can place the polylactic acid (PLA) and polybutylene terephthalate (PBT) to be compounded in a vacuum environment for drying, which can effectively remove the moisture in the PLA and PBT and obtain relatively pure PLA and PBT; then, the present application can place the dried PLA and PBT under successively increasing heating temperatures for mixing, which can improve the fluidity of the matrix and enable the two to be effectively mixed, and can avoid heating at the same temperature for a long time, thereby avoiding the low mechanical properties of the composite material particles obtained after mixing.

[0070] In a specific implementation, the present application can first weigh a certain mass fraction of PLA masterbatch and PBT fiber, wherein the proportion of PBT fiber in the total mass is 0.1%-0.5%, the PLA masterbatch can be selected from PLLA with a melt flow rate of 3-5g / 10min, and the PBT fiber can be selected from a density of 1.4g / cm 3 , PBT with a length of 3 mm and a diameter of 30 μm, then the PLA masterbatch and PBT fiber are placed in a vacuum environment for drying, and then the dried PLA masterbatch and PBT fiber are placed under successively rising heating temperatures for mixing to obtain composite material particles.

[0071] It should be noted that composite modification, as described in this application, refers to the mixing of a solid filler and a molten matrix to form a composite structure with a reinforcing phase; in contrast, blending modification refers to the mixing of two or more polymer materials in a molten state to form a macroscopically homogeneous material. There is a fundamental difference between the two. Therefore, in addition to the mass fraction of the fiber reinforcement phase, the mixing temperature is crucial; either too high or too low a temperature is detrimental to sample preparation. Therefore, in this application, when mixing the dried PLA masterbatch and PBT fiber at successively increasing heating temperatures, the heating temperature can be set to a minimum of 155-165°C and a maximum of 190-200°C. This ensures that during the processing, as the temperature gradually increases from the minimum (155-165°C) to the maximum (190-200°C), the PBT remains solid and the PLA is molten, achieving the desired composite effect. In addition, the set temperature range can also improve the flow properties of the materials, enable them to be fully mixed, and avoid excessively high or low heating temperatures, thereby preventing the final prepared composite material from having obvious defects such as stratification and porosity due to excessively high temperatures, or avoid problems such as poor compatibility and low mechanical properties caused by ineffective mixing due to excessively low temperatures.

[0072] Furthermore, since the composite material particles are granular, the present application can inject the composite material particles to obtain a composite material of a certain shape. Furthermore, before injecting the composite material particles into the composite material, in order to improve the molding effect of the injection molded part, the present application can first dry the composite material particles in a vacuum environment, and then inject the dried composite material particles into the composite material. This can not only obtain a composite material of a desired shape, but also improve the material quality of the composite material.

[0073] In one embodiment, drying the polylactic acid and polybutylene terephthalate under a vacuum environment in S110 may include:

[0074] S111: placing polylactic acid and polybutylene terephthalate in a vacuum drying oven, and drying them under vacuum environment at 100° C. for 2 hours.

[0075] In this embodiment, when PLA and PBT are placed in a vacuum environment for drying, the drying temperature and duration can be set according to the characteristics of PLA and PBT. This can effectively remove moisture from PLA and PBT and quickly obtain relatively pure PLA and PBT.

[0076] For example, the present application can place PLA and PBT in a vacuum drying oven, and set the drying temperature of the vacuum drying oven to 100° C. and the drying time to 2 hours, so as to obtain dehydrated PLA and PBT.

[0077] In one embodiment, in S120, mixing the dried polylactic acid and polybutylene terephthalate under successively increasing heating temperatures to obtain composite material particles may include:

[0078] S121: Add the dried polylactic acid and polybutylene terephthalate into a twin-screw mixing granulator for mixing to obtain composite material particles.

[0079] Wherein, the heating temperature of each heating zone of the twin-screw mixing granulator increases successively.

[0080] In this embodiment, when the dried polylactic acid and polybutylene terephthalate are placed under successively rising heating temperatures for mixing, a twin-screw mixing granulator can be used for mixing. During mixing, the dried polylactic acid and polybutylene terephthalate are added to the twin-screw mixing granulator for mixing, and the heating temperatures of each heating area of ​​the twin-screw mixing granulator are controlled to increase successively, so as to obtain composite material particles.

[0081] It is understood that plastic modification refers to the process of improving or increasing the functionality of general-purpose resins through physical, chemical, or mechanical methods to achieve the desired properties for use under specific environmental conditions in terms of electrical, magnetic, optical, thermal, aging resistance, flame retardancy, and mechanical properties. In the process of plastic modification, a twin-screw mixing and granulating machine, also known as a twin-screw extruder, is generally used. For example, a plastic matrix, auxiliary materials, and additives are mixed, kneaded, melted, sheared, and extruded through a series of processes in a twin-screw extruder to produce high-performance specialized materials, such as the composite material particles of the present application.

[0082] Among them, the twin-screw mixing granulator of the present application can be divided into multiple heating zones according to the various stages of its mixing process, and the temperature of each heating zone can be set so that the heating temperature of each heating zone increases sequentially, which can not only improve the mixing effect, but also improve the mechanical properties of the PLA material.

[0083] In one embodiment, the rotation speed of the twin-screw mixer granulator is 30 rpm.

[0084] In this embodiment, since the speed of the twin-screw mixing granulator also affects the mixing quality, if the speed is too low, PLA and PBT cannot be fully mixed, and the composite material prepared in this way has poor compatibility and low mechanical properties. If the speed is too high, the material stays in the screw for a short time, and the mixing effect will also be affected.

[0085] Therefore, when feeding PLA and PBT into the twin-screw mixing granulator for mixing, the speed of the twin-screw mixing granulator can be set to 30 rpm. This can not only ensure that the materials are fully mixed, but also avoid the situation where too high or too low speeds lead to poor compatibility and low mechanical properties. Of course, in actual applications, the speed can also be set accordingly according to the amount of material fed and the specifications of the material, and this is not limited here.

[0086] In one embodiment, the twin-screw mixing granulator may include a conveying section, a melting section, a mixing section, a venting section, and a homogenizing section.

[0087] Wherein, the heating temperature of the conveying section is 160°C.

[0088] The heating temperature of the melting section is 170°C.

[0089] The heating temperature of the mixing section is 180°C.

[0090] The heating temperature of the exhaust section is 190°C.

[0091] The heating temperature of the homogenization section is 195°C.

[0092] In this embodiment, multiple heating zones can be divided according to the various stages of the mixing process of the twin-screw mixer granulator. For example, according to a series of processes such as mixing, kneading, melting, shearing, and extrusion of the twin-screw mixer granulator, it can be divided into a conveying section, a melting section, a kneading section, a venting section, and a homogenizing section. After each section is used as a heating zone, the temperature of each heating zone is set so that the heating temperature of each heating zone increases sequentially. This can not only improve the mixing effect, but also improve the mechanical properties of the PLA material.

[0093] Among them, the heating temperature of the conveying section should not be too high, which will easily affect the conveying and shearing of the material in this section. The heating temperature of the conveying section should not be too low either, which will cause the screw to be overstressed or stuck. The heating temperature of the conveying section is generally set to be slightly close to the temperature of the melting section; the heating temperature of the melting section can be set to a temperature slightly higher than the melting point range of the base material based on the different base materials and glass fiber content, as well as the melt flow conditions of the rear section of the melting section (i.e., the glass fiber addition inlet), and after deducting the heat input by the screw shear; and the temperature of the mixing section is too low, which will lead to This results in poor material flowability, high viscosity, increased friction, high heat generation, and local overheating. If the temperature of the mixing section is too high, it will lead to resin degradation, low shear rate, and poor dispersion of glass fiber. Therefore, when setting the heating temperature of the mixing section, it can be determined based on the content of base material and glass fiber, the melting point range of the base material, and the glossiness of the finished strips; further, when setting the heating temperature of the exhaust section, the present application can set a heating temperature slightly higher than the mixing section on the basis of the heating temperature of the mixing section, and the temperature of the homogenizing section can also be determined according to the glossiness of the finished strips.

[0094] Specifically, the present application can set the heating temperature of the conveying section to 160°C, the heating temperature of the melting section to 170°C, the heating temperature of the mixing section to 180°C, the heating temperature of the exhaust section to 190°C, and the heating temperature of the homogenization section to 195°C. This can ensure that the temperatures of each heating area increase sequentially, and can also ensure that the minimum heating temperature of the twin-screw mixing granulator is 155-165°C and the maximum heating temperature is 190-200°C, thereby avoiding obvious defects such as delamination and porosity in the composite material due to excessively high temperature, or avoiding problems such as poor compatibility and low mechanical properties due to ineffective mixing due to too low temperature.

[0095] In one embodiment, placing the composite material particles in a vacuum environment for drying in S130 may include:

[0096] S131: placing the composite material particles in a vacuum drying oven and drying them in a vacuum environment at 100° C. for 2 hours.

[0097] In this embodiment, when the composite material particles are placed in a vacuum environment for drying, the drying temperature and duration can be set according to the characteristics of the composite material particles. This can effectively remove moisture from the composite material particles and quickly obtain relatively pure composite material particles.

[0098] For example, the present application can place the composite material particles in a vacuum drying oven, and set the drying temperature of the vacuum drying oven to 100° C. and the drying time to 2 hours, so as to obtain dehydrated composite material particles.

[0099] In one embodiment, injection molding the dried composite material particles to obtain the polymer composite material in S140 may include:

[0100] S141: Adding the dried composite material particles into a horizontal injection molding machine for injection molding to obtain a polymer composite material.

[0101] In this embodiment, when the dried composite material particles are injection molded, a horizontal injection molding machine can be selected. Specifically, during operation, the present application can add the dried composite material particles into the horizontal injection molding machine for injection molding, so that a polymer composite material can be obtained.

[0102] It is understandable that in traditional technology, injection molding machines can generally be divided into vertical, horizontal, and vertical-horizontal composite types according to the arrangement of the injection device and the clamping device. The present application can use a horizontal injection molding machine to perform injection molding of composite material particles. The clamping part and the injection part of the horizontal injection molding machine are on the same horizontal center line, and the mold is opened in the horizontal direction, so it is easy to operate and maintain; and its machine has a low center of gravity and is relatively stable to install. After the product is ejected, it can automatically fall down by gravity, and it is easy to achieve fully automatic operation. Of course, the present application can also choose a vertical or vertical-horizontal composite injection molding machine according to actual needs, and there is no restriction here.

[0103] The present application uses a horizontal injection molding machine to perform injection molding on composite material particles, which can quickly obtain a polymer composite material.

[0104] In one embodiment, the injection temperatures of the barrel sections of the horizontal injection molding machine are 170°C, 180°C, 190°C, and 195°C, respectively.

[0105] The injection speed of the horizontal injection molding machine is 40 mm / s.

[0106] In this embodiment, when using a horizontal injection molding machine to injection mold composite material particles, the electric heating can be turned on to heat each section of the barrel. When the temperature of each section reaches the required level, the temperature is then maintained for a period of time to stabilize the machine temperature. The heating temperature and holding time can be set according to the requirements of different equipment and plastic raw materials.

[0107] In an embodiment of the present application, when a horizontal injection molding machine is used for injection molding, the injection temperatures of each section of the barrel can be set to 170°C, 180°C, 190°C, and 195°C in sequence, and the injection speed of the horizontal injection molding machine is 40 mm / s. This can not only control the horizontal injection molding machine for stable processing, but also improve the production quality and production efficiency of the product.

[0108] Optionally, the method may further include:

[0109] When polylactic acid and polybutylene terephthalate are placed in a vacuum environment for drying, polyethylene glycol with a mass fraction of 1%-2% is added and dried and mixed together.

[0110] In this embodiment, when compounding PLA and PBT fibers, 1% to 2% by mass of PEG (polyethylene glycol) can be added. This can not only improve the fluidity and dispersion effect during mixing, but also increase the production yield of injection molded parts.

[0111] Furthermore, the present application comprehensively describes the polymer composite material and its preparation method through the above-mentioned multiple embodiments. However, in order to better illustrate the beneficial effects of the composite material prepared by the present application, the present application introduces the following multiple comparative examples for comparative analysis with the multiple embodiments of the present application, as follows:

[0112] Example 1:

[0113] Weigh a certain mass fraction of PLA masterbatch (left-handed, melt flow rate 3-5g / 10min) and a mass fraction of 0.1wt% of original PBT fiber (density 1.4g / cm 3 , length 3 mm, diameter 30 μm) were placed in a vacuum drying oven and dried under vacuum and 100 ° C for 2 hours. The dried PLA masterbatch and PBT fiber were added to a twin-screw mixing granulator to form composite particles. The temperatures of different heating zones were set to 160-170-180-190-195 ° C. The composite particles were then placed in a vacuum drying oven and dried under vacuum and 100 ° C for 2 hours. Finally, a horizontal injection molding machine was used to prepare the composite particles into test specimens. The injection temperature was 170-180-190-195 ° C and the injection speed was 40 mm / s.

[0114] Example 2:

[0115] The difference from Example 1 is that the mass fraction of the added original PBT fiber is 0.3 wt %.

[0116] Example 3:

[0117] The difference from Example 1 is that the mass fraction of the added original PBT fiber is 0.5 wt %.

[0118] Example 4:

[0119] The difference from Example 1 is that the added PBT fiber is recycled PBT fiber.

[0120] Example 5:

[0121] The difference from Example 4 is that the mass fraction of the added recycled PBT fiber is 0.3 wt %.

[0122] Example 6:

[0123] The difference from Example 4 is that the mass fraction of the added recycled PBT fiber is 0.5 wt %.

[0124] Comparative Example 1:

[0125] The difference from Example 1 is that: poplar wood powder (density 1.4g / cm 3 , average length 0.4 mm, average diameter 80 μm) was used to replace the PBT fiber, and 4% mass fraction of silane coupling agent (KH-570) was added during the mixing process, and the rest of the steps were the same.

[0126] Comparative Example 2:

[0127] The difference from Comparative Example 1 is that the mass fraction of the added poplar wood powder is 0.3 wt %.

[0128] Comparative Example 3:

[0129] The difference from Comparative Example 1 is that the mass fraction of the added poplar wood powder is 0.5 wt %.

[0130] Comparative Example 4:

[0131] The difference from Example 1 is that the mass fraction of the added original PBT fiber is 0.6 wt %.

[0132] Comparative Example 5:

[0133] The difference from Example 1 is that the temperatures of different heating zones in the twin-screw mixing granulator are set to 170-180-190-200-205°C.

[0134] Comparative Example 6:

[0135] The difference from Example 1 is that the temperatures of different heating zones in the twin-screw mixing granulator are set to 150-160-170-180-185°C.

[0136] After the mechanical properties of the composite materials prepared by the above-mentioned multiple embodiments and multiple comparative examples are analyzed, the analysis results shown in Figures 2 and 3 can be obtained, wherein Figure 2 is a graph of the elongation at break of different reinforcing fiber volume fractions provided by the embodiment of the present application, and Figure 3 is a graph of the impact strength of different reinforcing fiber volume fractions provided by the embodiment of the present application; It can be seen from Figure 2 that when the mixing temperature is kept constant, the elongation at break of the composite material decreases with the increase of the mass fraction of the original PBT fiber / recycled PBT fiber / wood fiber (poplar wood powder), wherein when the original PBT fiber and the recycled PBT When the mass fraction of the fiber accounts for 0.1%-0.5% of the total mass proportion, the elongation at break of the composite material is still at a high level; when the mass fraction of the original PBT fiber and the recycled PBT fiber accounts for more than 0.1%-0.5% of the total mass proportion, the mechanical properties of the composite material are significantly reduced, as shown in Table 1 below; and when poplar wood powder is used to replace PBT fiber, the elongation at break of the composite material shows a significant decreasing trend with the increase of the mass fraction of poplar wood powder. Therefore, this application uses original PBT fiber and recycled PBT fiber with PLA masterbatch to obtain a composite material with higher mechanical properties.

[0137] Similarly, as shown in Figure 3, when the present application uses 0.1%-0.5% mass fraction of original PBT fiber or recycled PBT fiber for composite modification, the impact strength of the composite material is significantly stronger than the impact strength of using poplar wood powder, and the effect is best when 0.5% mass fraction of original PBT fiber or recycled PBT fiber is used for composite modification.

[0138] Table 1

[0139]

[0140] Table 1 shows the compounding process and compounding results of various examples and comparative examples. It should be noted that the PBT fiber in Table 1 refers to the original PBT fiber, and the rPBT fiber refers to the recycled PBT fiber.

[0141] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0142] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0143] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A polymer composite material, characterized in that: The composite material comprises polylactic acid and polybutylene terephthalate; Wherein, the polybutylene terephthalate accounts for 0.1%-0.5% of the total mass proportion.

2. The polymer composite material according to claim 1, characterized in that: The composite material also includes polyethylene glycol; The polyethylene glycol accounts for 1%-2% of the total mass ratio.

3. The polymer composite material according to claim 1 or 2, characterized in that: The polylactic acid is L-polylactic acid; The melt flow rate of the L-polylactic acid is 3-5 g / 10 min.

4. The polymer composite material according to any one of claims 1 to 3, characterized in that: The density of the polybutylene terephthalate is 1.4 g / cm 3 , length 3mm, diameter 30μm.

5. A method for preparing a polymer composite material according to any one of claims 1 to 4, characterized in that: The method comprises: Placing polylactic acid and polybutylene terephthalate in a vacuum environment for drying, wherein the polybutylene terephthalate accounts for 0.1%-0.5% of the total mass ratio; The dried polylactic acid and polybutylene terephthalate are placed under successively increasing heating temperatures for mixing to obtain composite material particles, wherein the heating temperature is at least 155-165° C. and at most 190-200° C.; placing the composite material particles in a vacuum environment for drying; The dried composite material particles are injection molded to obtain a polymer composite material.

6. The preparation method according to claim 5, characterized in that: The dried polylactic acid and polybutylene terephthalate are placed under successively increasing heating temperatures for mixing to obtain composite material particles, comprising: Adding the dried polylactic acid and polybutylene terephthalate into a twin-screw mixing granulator for mixing to obtain composite material particles; Wherein, the heating temperature of each heating zone of the twin-screw mixing granulator increases successively.

7. The preparation method according to claim 6, characterized in that: The twin-screw mixing granulator comprises a conveying section, a melting section, a mixing section, a venting section, and a homogenizing section; Wherein, the heating temperature of the conveying section is 160°C; The heating temperature of the melting section is 170°C; The heating temperature of the mixing section is 180°C; The heating temperature of the exhaust section is 190°C; The heating temperature of the homogenization section is 195°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The method of injection molding the dried composite material particles to obtain the polymer composite material comprises: The dried composite material particles are added into a horizontal injection molding machine for injection molding to obtain a polymer composite material.

9. The preparation method according to claim 8, characterized in that: The injection temperatures of the barrel sections of the horizontal injection molding machine are 170°C, 180°C, 190°C, and 195°C, respectively; The injection speed of the horizontal injection molding machine is 40 mm / s.

10. The preparation method according to any one of claims 5 to 9, characterized in that: The method further comprises: When polylactic acid and polybutylene terephthalate are dried under a vacuum environment, 1% to 2% by mass of polyethylene glycol is added and dried and mixed together.

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