Lightweight high-strength plastic material and method for its production

Abstract

The application relates to the field of plastic materials, in particular to a light-weight high-strength plastic material and a preparation method thereof, which is prepared by injection molding foaming of a polypropylene component, a thermotropic liquid crystal polymer and an additive; the polypropylene component comprises functionalized polypropylene, and the functionalized polypropylene is obtained by modifying polypropylene by a double-bond liquid crystal monomer and maleic anhydride; the prepared plastic material has the technical effect of being light-weight and high-strength, and has wide application prospects in many fields such as daily necessities, automobiles, household appliances and packaging.

Description

Technical Field

[0001] This invention relates to the field of plastic materials, specifically to a lightweight, high-strength plastic material and its preparation method. Background Technology

[0002] Polypropylene, as one of the five most widely used general-purpose plastics, is characterized by its low price, heat resistance, chemical resistance, ease of molding and processing, and excellent mechanical properties, making it widely used in many fields such as automobiles, home appliances, and packaging. However, how to reduce its density without significantly affecting its strength to meet the needs of more application scenarios is currently a research hotspot. Summary of the Invention

[0003] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a lightweight, high-strength plastic material and its preparation method.

[0004] The technical solution adopted is as follows:

[0005] A lightweight, high-strength plastic material is made by injection molding foaming of polypropylene components, thermotropic liquid crystal polymers, and additives;

[0006] The polypropylene component includes functionalized polypropylene, which is obtained by modifying polypropylene with double-bonded liquid crystal monomers and maleic anhydride.

[0007] Furthermore, the polypropylene component contains ≥10 wt% functionalized polypropylene, with the remainder being polypropylene.

[0008] Furthermore, the mass ratio of the polypropylene component, the thermotropic liquid crystal polymer, and the additives is 1:0.05-0.1:0.01-0.05.

[0009] Furthermore, the structural formula of the double-bonded liquid crystal monomer is as follows:

[0010]

[0011] R1 and R2 may be the same or different, and each is an alkyl group.

[0012] Furthermore, R1 and R2 are the same.

[0013] Furthermore, R1 and R2 are alkyl groups with ≥6 carbon atoms.

[0014] Furthermore, the preparation method of the functionalized polypropylene is as follows:

[0015] Functionalized polypropylene is obtained by uniformly mixing double-bonded liquid crystal monomers, maleic anhydride, and free radical initiators with polypropylene and then melt-extending the mixture through a twin-screw extruder.

[0016] Furthermore, the mass ratio of the polypropylene, the double-bonded liquid crystal monomer, and the maleic anhydride is 1:0.01-0.05:0.01-0.05.

[0017] Furthermore, the additives include any one or any combination of two or more of antioxidants, light stabilizers, flame retardants, lubricants, and nucleating agents.

[0018] This invention also provides a method for preparing a lightweight, high-strength plastic material:

[0019] After the polypropylene component, thermotropic liquid crystal polymer and additives are mixed evenly, they are added to a twin-screw extruder for melt extrusion granulation. The resulting granules are added to an injection molding machine, and supercritical CO2 is injected into the screw homogenization zone of the injection molding machine. Under the shearing of the screw, the supercritical CO2 and granules are mixed into a melt. The melt is injected into the mold cavity through a self-locking nozzle. Finally, the mold is opened and the pressure is released to allow the CO2 to escape, thus obtaining the lightweight and high-strength plastic material.

[0020] It has the following beneficial effects:

[0021] This invention provides a lightweight, high-strength plastic material. In recent years, there have been many reports on obtaining composite materials by in-situ reinforcing polypropylene with thermotropic liquid crystal polymers during processing. However, there have been no reports on co-injection molding and foaming polypropylene and thermotropic liquid crystal polymers. In this invention, the rigid molecular chains of the thermotropic liquid crystal polymer can form a highly oriented structure in the molten state, which can significantly improve the strength of the polypropylene melt. This enhances the melt's ability to restrict rapid gas escape during the foaming and expansion process. During cell growth, the cell walls can withstand stronger tensile stress without easily breaking or merging. This allows for a more stable and uniform process of cell nucleation and growth, resulting in improved cell structure, namely, smaller and more uniform cell size, fewer broken cells, and higher integrity of the closed-cell structure. This, in turn, improves the mechanical strength of the plastic material.

[0022] Because thermotropic liquid crystal polymers and polypropylene matrix resins have poor compatibility, it can affect the performance of plastic materials. In this invention, functionalized polypropylene can enhance the adhesion between the two phases, prevent phase separation, and improve the mechanical properties of plastic materials. The double-bonded liquid crystal monomer, as a functionalized graft monomer, not only has liquid crystal properties but also has a structure similar to the rigid rod-like structure of the thermotropic liquid crystal polymer backbone. Therefore, it can serve as an intermediate phase to improve the compatibility between thermotropic liquid crystal polymers and polypropylene matrix resins. The alkyl branches in the structure can further enhance the melt strength through the physical cross-linking of molecular chains, thereby inhibiting the merging and rupture of bubbles during foaming. Furthermore, by regulating the nucleation density and gas diffusion behavior, it can improve the uniformity of the cells and enhance the mechanical properties of plastic materials.

[0023] The plastic material prepared by this invention has the technical advantages of being lightweight and high-strength, and has broad application prospects in many fields such as daily necessities, automobiles, home appliances, and packaging. Detailed Implementation

[0024] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0025] Example 1:

[0026] A method for preparing a lightweight, high-strength plastic material:

[0027] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.05:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0028] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0029] The thermotropic liquid crystal polymer is Vectra A 950;

[0030] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0031] The preparation method of functionalized polypropylene is as follows:

[0032] Functionalized polypropylene is obtained by uniformly mixing double-bonded liquid crystal monomers, maleic anhydride, and free radical initiator DCP in a mass ratio of 0.02:0.01:0.0015:1 with general-purpose polypropylene and then melt-extruding the mixture through a twin-screw extruder at 190-220℃.

[0033] The preparation method of double-bonded liquid crystal monomers is as follows:

[0034]

[0035] 82.5 g (0.4 mol) of p-hydroxyphenylheptanone was dissolved in 500 mL of ethanol. Then, 10 g (0.2 mol) of hydrazine hydrate was added dropwise to the reaction solution while stirring continuously. After stirring for 10 min, a small amount of hydrochloric acid solution was added as a catalyst. The reaction was carried out continuously at 70 °C for 12 h, and then the reaction was stopped and cooled overnight. The precipitated solid was filtered off and recrystallized with anhydrous ethanol to obtain the intermediate with a yield of 84.9%.

[0036]

[0037] 24.64 g (0.06 mol) of the intermediate and 10.68 g (0.06 mol) of allyloxybenzoic acid were dissolved in 250 mL of tetrahydrofuran and placed in a flask for reaction. Then, 14.83 g (0.07 mol) of DCC and 0.73 g (0.006 mol) of DMAP were dissolved in 150 mL of tetrahydrofuran. Under stirring, the DCC / DMAP mixed solution was added dropwise to the solution in the round-bottom flask. After stirring and reacting at room temperature for 24 h, the resulting white byproduct was filtered off. The filtrate was then removed by vacuum rotary evaporation to remove excess tetrahydrofuran solution, yielding the crude product. The crude product was purified by recrystallization with ethanol and dried to obtain the double-bonded liquid crystal monomer, with a yield of 77.3%. ESI-MS (m / z) (M + Theoretical value: 568.76, measured value: 568.24.

[0038] Example 2:

[0039] A method for preparing a lightweight, high-strength plastic material:

[0040] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.06:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60 MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0041] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0042] The thermotropic liquid crystal polymer is Vectra A 950;

[0043] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0044] The preparation method of functionalized polypropylene is the same as in Example 1.

[0045] Example 3:

[0046] A method for preparing a lightweight, high-strength plastic material:

[0047] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.07:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60 MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0048] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0049] The thermotropic liquid crystal polymer is Vectra A 950;

[0050] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0051] The preparation method of functionalized polypropylene is the same as in Example 1.

[0052] Example 4:

[0053] A method for preparing a lightweight, high-strength plastic material:

[0054] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.08:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60 MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0055] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0056] The thermotropic liquid crystal polymer is Vectra A 950;

[0057] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0058] The preparation method of functionalized polypropylene is the same as in Example 1.

[0059] Example 5:

[0060] A method for preparing a lightweight, high-strength plastic material:

[0061] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.09:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60 MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0062] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0063] The thermotropic liquid crystal polymer is Vectra A 950;

[0064] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0065] The preparation method of functionalized polypropylene is the same as in Example 1.

[0066] Example 6:

[0067] A method for preparing a lightweight, high-strength plastic material:

[0068] A polypropylene component, thermotropic liquid crystal polymer, and additives in a mass ratio of 1:0.1:0.05 are added to a high-speed mixer and mixed evenly to obtain a mixture. The mixture is then added to a twin-screw extruder for melt extrusion granulation. The temperature of the twin-screw extruder is 180-295℃, and the screw speed is 50 r / min. The obtained granules are cooled and air-dried, then added to the barrel of an injection molding machine and heated to about 300℃ to melt them. Supercritical CO2 is injected into the screw homogenization zone of the injection molding machine using a supercritical gas injection system. Under the shearing of the screw, the supercritical CO2 is mixed with the molten granules to form a melt. The melt is injected into the mold cavity at a temperature of 50℃ through a self-locking nozzle. The injection temperature is 285℃, and the injection pressure is 60MPa. Finally, the mold is quickly opened to release pressure and allow the CO2 to escape, thus obtaining the lightweight high-strength plastic material.

[0069] The polypropylene component consists of general-purpose polypropylene and functionalized polypropylene in a mass ratio of 9:1.

[0070] The thermotropic liquid crystal polymer is Vectra A 950;

[0071] The additives consist of antioxidant 1010, polypropylene wax lubricant Licocene PP 6102FG, and nucleating agent ADK-STAB NA21 in a mass ratio of 2:1:2.

[0072] The preparation method of functionalized polypropylene is the same as in Example 1.

[0073] Comparative Example 1:

[0074] It is basically the same as Example 1, except that no thermotropic liquid crystal polymer is added.

[0075] Comparative Example 2:

[0076] It is basically the same as Example 1, except that the polypropylene component contains only general-purpose polypropylene.

[0077] Comparative Example 3:

[0078] It is basically the same as Example 1, except that no double-bonded liquid crystal monomers are added during the preparation of functionalized polypropylene.

[0079] The preparation method of functionalized polypropylene is as follows:

[0080] Functionalized polypropylene is obtained by uniformly mixing maleic anhydride and free radical initiator DCP in a mass ratio of 0.01:0.0015:1 with general-purpose polypropylene and then melt-extruding the mixture through a twin-screw extruder at 190-220℃.

[0081] Performance testing

[0082] The plastic materials from Examples 1-6 and Comparative Examples 1-3 were respectively made into test specimens for performance testing;

[0083] The tensile strength, bending strength and notched impact strength of the specimens were tested using a universal testing machine and a pendulum impact testing machine, respectively.

[0084] Tensile properties were tested according to ISO 527-2-1993 standard, with a tensile rate of 50 mm / min;

[0085] Bending performance was tested according to ISO 178-2010 standard, with a span of 64 mm and a bending rate of 2 mm / min;

[0086] Notched impact strength was tested according to ISO 180-2000 standard, with a notch depth of 2 mm;

[0087] The test results are shown in Table 1 below:

[0088] Table 1:

[0089]

[0090]

[0091] As can be seen from Table 1 above, the plastic material prepared by the present invention has the technical effect of being lightweight and high-strength;

[0092] A comparison of Examples 1-6 shows that the relevant properties change as the amount of thermotropic liquid crystal polymer increases.

[0093] The comparison between Example 1 and Comparative Example 1 shows that the addition of thermotropic liquid crystal polymers plays a positive role in reducing the density of plastic materials and improving their mechanical strength.

[0094] The comparison between Example 1 and Comparative Example 2 shows that the addition of functionalized polypropylene plays a positive role in improving the mechanical strength of plastic materials.

[0095] The comparison between Example 1 and Comparative Example 3 shows that the addition of double-bonded liquid crystal monomers during the preparation of functionalized polypropylene plays a positive role in improving the mechanical strength of the plastic material.

[0096] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lightweight, high-strength plastic material, characterized in that, It is made by injection molding and foaming of polypropylene components, thermotropic liquid crystal polymers, and additives; The polypropylene component includes functionalized polypropylene, which is obtained by modifying polypropylene with double-bonded liquid crystal monomers and maleic anhydride. The polypropylene component contains ≥10 wt% functionalized polypropylene, with the remainder being polypropylene. The mass ratio of the polypropylene component, the thermotropic liquid crystal polymer, and the additives is 1:0.05-0.1:0.01-0.05; The structural formula of the double-bonded liquid crystal monomer is as follows: R1 and R2 are the same and are alkyl groups with ≥6 carbon atoms.

2. The lightweight, high-strength plastic material as described in claim 1, characterized in that, The preparation method of the functionalized polypropylene is as follows: Functionalized polypropylene is obtained by uniformly mixing double-bonded liquid crystal monomers, maleic anhydride, and free radical initiators with polypropylene and then melt-extending the mixture through a twin-screw extruder.

3. The lightweight, high-strength plastic material as described in claim 2, characterized in that, The mass ratio of the polypropylene, double-bonded liquid crystal monomer, and maleic anhydride is 1:0.01-0.05:0.01-0.

05.

4. The lightweight, high-strength plastic material as described in claim 1, characterized in that, The additives include any one or any combination of two or more of the following: antioxidants, light stabilizers, flame retardants, lubricants, and nucleating agents.

5. A method for preparing a lightweight, high-strength plastic material as described in any one of claims 1-4, characterized in that, After the polypropylene component, thermotropic liquid crystal polymer and additives are mixed evenly, they are added to a twin-screw extruder for melt extrusion granulation. The resulting granules are added to an injection molding machine, and supercritical CO2 is injected into the screw homogenization zone of the injection molding machine. Under the shearing of the screw, the supercritical CO2 and granules are mixed into a melt. The melt is injected into the mold cavity through a self-locking nozzle. Finally, the mold is opened and the pressure is released to allow the CO2 to escape, thus obtaining the lightweight and high-strength plastic material.

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