Polylactic acid-plant fiber environment-friendly flame-retardant material for plates as well as preparation method and application thereof

Abstract

The invention provides a polylactic acid-plant fiber environment-friendly flame-retardant material for plates as well as a preparation method and application thereof. Polydimethylsiloxane with reactive functional groups at two ends is used as a modifier for the polylactic acid composition, and a polysiloxane chain segment is introduced into a main chain of a polylactic acid molecule, so that the elongation at break, the impact strength and the heat resistance of the polylactic acid-plant fiber environment-friendly flame-retardant material are improved. For plant fibers, pectin components in the plant fibers are removed through alkali treatment, then an organic silicon coupling agent is used for treatment, the organic silicon coupling agent and hydroxyl groups of cellulose form a multi-site hydrogen bond coupling effect, the organic silicon coupling agent is adsorbed on the surface of the cellulose, and therefore the compatibility of the cellulose and polylactic acid molecules modified by polysiloxane chain segments is improved; therefore, the mechanical property, heat resistance and flame retardance of the environment-friendly flame-retardant material are further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polylactic acid composite materials, and specifically to a polylactic acid composition, a polylactic acid-plant fiber environmentally friendly flame retardant material for a plate, and a preparation method and application thereof. Background Art

[0002] Polypropylene material has the advantages of low density, high strength, and corrosion resistance, and is widely used in automotive interior parts. However, polypropylene has defects such as insufficient impact strength and easy deformation, poor aging resistance, and poor scratch resistance. After fiber reinforcement, it has good strength and rigidity, and the impact strength is also greatly improved. This type of fiber-reinforced polypropylene composite material not only reduces the weight of the entire interior, but also increases the design freedom of the product. However, this reinforced composite material still uses traditional petroleum-based materials such as polypropylene and polyethylene. Petroleum-based materials have poor biodegradability and cannot be self-degraded after being discarded, causing environmental pollution. Moreover, as oil resources gradually dry up, the production cost of petroleum-based materials has gradually increased, driving the cost of automotive interior materials to increase.

[0003] Due to concerns about the environment and sustainable development, research efforts on natural polymers and biodegradable polymers have been intensified. For example, natural fibers such as plant fibers, how to improve the utilization rate of plant fibers through modification and blending, and bio-based composite materials containing plant fibers have become hot topics in research on green and environmentally friendly polymers.

[0004] On the other hand, polylactic acid is derived from renewable crops such as corn and cassava. Compared with other biodegradable polymers, it has the advantages of high strength and high modulus. Compared with the currently commonly used petroleum-based materials such as polypropylene and polyethylene, polylactic acid can be biodegraded in a shorter period of time and has the advantage of being green and environmentally friendly. However, the preparation cost of polylactic acid is relatively high. The polylactic acid composite material prepared by compounding polylactic acid and plant fibers can effectively reduce the production cost. The composite material of polylactic acid and plant fibers realizes the diversification, lightness, environmental protection and low cost of automotive interior panels.

[0005] However, the addition of plant fibers will cause the structure of polylactic acid to be destroyed, resulting in the mechanical properties of polylactic acid-fiber composites being worse than those of pure polylactic acid materials. This is because polylactic acid itself has poor water resistance and is prone to ester bond hydrolysis. The small molecules of water carried by the plant fibers are transferred to the surface of polylactic acid and diffuse into the ester bonds or around the hydrophilic groups, causing the ester bonds to undergo free hydrolysis and break, resulting in a decrease in the molecular weight of polylactic acid and a destruction of the chemical structure, which in turn makes the mechanical properties of polylactic acid-plant fiber composites worse than those of pure polylactic acid materials. In addition, the polarity of the chemical structures of polylactic acid and plant fibers is greatly different, and the interaction between them is weak. In addition, the fiber as a blending component cannot effectively increase the crystallization rate of polylactic acid, resulting in poor mechanical properties and heat resistance of the composite material. Summary of the invention

[0006] The purpose of the present invention is to overcome the above shortcomings and to propose a polylactic acid composition with added modifier, a polylactic acid-plant fiber environmentally friendly flame retardant material for panels, and corresponding high-toughness interior panels and flame retardant partition composite panels.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows: In a first aspect, a polylactic acid composition comprises polylactic acid, a modifier, a flame retardant, a cross-linking agent and a nucleating agent.

[0008] The modifier is a terminal functionalized polydimethylsiloxane, and terminal functionalization means that both ends of the linear polydimethylsiloxane have terminal functional groups, and the terminal functional groups include: carboxyl, hydroxyl, amino, and epoxy. At the same time, the side chains of the modifier molecules are all methyl groups, and no functional groups exist.

[0009] Preferably, the terminal functionalized polydimethylsiloxane is selected from any one or a combination of carboxyl-terminated polydimethylsiloxane, hydroxyl-terminated polydimethylsiloxane, amino-terminated polydimethylsiloxane or epoxy-terminated polydimethylsiloxane.

[0010] The flame retardant includes a phosphorus-based flame retardant, a nitrogen-based flame retardant and a polyol, wherein the phosphorus-based flame retardant is selected from any one of ammonium polyphosphate and organic phosphate or a combination of two thereof.

[0011] The nitrogen flame retardant is selected from any one or a combination of melamine, melamine cyanurate or dicyandiamide.

[0012] The polyol is selected from any one or a combination of monopentaerythritol, dipentaerythritol, trimethylolpropane or trimethylolethane.

[0013] The crosslinking agent is a difunctional crosslinking agent selected from a diene crosslinking agent containing a bisphenol A core. Preferably, the diene crosslinking agent containing a bisphenol A core includes any one of bisphenol A diallyl ether and 2,2'-diallyl bisphenol A or a combination of both.

[0014] The nucleating agent is selected from talc powder, and preferably, the particle size of the talc powder is not more than 10 μm.

[0015] Furthermore, based on the mass of the polylactic acid, the amount of the modifier is 1-15wt%, preferably, the amount of the modifier is 5-15wt%, and more preferably, the amount of the modifier is 5-10wt%.

[0016] The amount of the flame retardant is 1-15 wt %, preferably, the amount of the flame retardant is 5-15 wt %, and more preferably, the amount of the flame retardant is 5-10 wt %.

[0017] The amount of the crosslinking agent is 1-5 wt %, preferably 1-3 wt %.

[0018] The amount of the nucleating agent is 0.5-5wt%, preferably, the amount of the nucleating agent is 0.5-3wt%.

[0019] In a second aspect, a polylactic acid-plant fiber environmentally friendly flame retardant material for a board material comprises the polylactic acid composition and the plant fiber described above.

[0020] The plant fiber is selected from any one of cotton fiber, hemp fiber and wood fiber. The cotton fiber is preferably cotton fiber, and the hemp fiber is preferably sisal fiber.

[0021] The length of the plant fiber is 5 to 15 mm, preferably, the length of the plant fiber is 10 to 15 mm.

[0022] The plant fiber is firstly treated with alkali and then treated with an aqueous solution of an organic silicon coupling agent, wherein the organic silicon coupling agent is a linear or cyclic polysiloxane grafted with a polyoxyethylene ether chain segment.

[0023] Furthermore, the alkali treatment is to soak the plant fibers in a sodium hydroxide solution, then wash them until the pH is neutral, and then dry them; the organic silicon coupling agent aqueous solution treatment is to soak the plant fibers after the alkali treatment in an organic silicon coupling agent aqueous solution.

[0024] Preferably, the concentration of the sodium hydroxide solution used in the alkali treatment is 10 wt %.

[0025] Preferably, the concentration of the organic silicon coupling agent aqueous solution used for the organic silicon coupling agent aqueous solution treatment is 10 wt %.

[0026] In the third aspect, the preparation method of the above-mentioned polylactic acid-plant fiber environmentally friendly flame retardant material for panels includes: mixing and compression molding, wherein the mixing specifically includes: melting and mixing polylactic acid, modifier, flame retardant, cross-linking agent and nucleating agent on a plasticizer, and then adding plant fiber for mixing.

[0027] Preferably, the mixing temperature is higher than the melting point of polylactic acid, and more preferably, the mixing temperature is 175-210° C.; the compression molding comprises: compression molding the mixed material at a temperature of 175-210° C. and a pressure of 10-20 MPa.

[0028] Preferably, the molding time is 1 to 20 minutes.

[0029] Preferably, the material is vacuumed during the compression molding process.

[0030] Preferably, after the compression molding is completed, the temperature is further lowered to room temperature for cold pressing, and the cold pressing time is 10 to 30 minutes.

[0031] Fourthly, the polylactic acid-plant fiber environmentally friendly flame retardant material for panels mentioned above is used in automotive interior panels, lighting decorative panels, and automotive partition composite panels.

[0032] In a fifth aspect, a high-toughness flame-retardant interior panel is prepared from the above-mentioned polylactic acid-plant fiber environmentally friendly flame-retardant material for panels.

[0033] In a sixth aspect, a flame retardant partition composite board is prepared from the above-mentioned polylactic acid-plant fiber environmentally friendly flame retardant material for boards.

[0034] In a seventh aspect, a motorhome comprises at least one of the high-toughness flame-retardant interior panels and flame-retardant partition composite panels described above.

[0035] The beneficial effects of the present invention are as follows: first, polydimethylsiloxane with reactive functional groups at both ends is used as a modifier for a polylactic acid composition, and the functional groups at both ends react with the hydroxyl or carboxyl groups at the ends of the polylactic acid molecular chain during high-temperature mixing, thereby introducing polysiloxane segments into the polylactic acid main chain, and the polysiloxane segments have good softness and elasticity, can adapt to surfaces of different shapes and provide effective coverage, thereby improving the elongation at break and impact strength of the polylactic acid-plant fiber environmentally friendly flame retardant material, and at the same time, compared with the carbon-based main chain, the polysiloxane segments are more difficult to decompose at high temperatures, thereby improving the deformation temperature of the environmentally friendly flame retardant material. For the treatment of plant fibers, the basic alkali solution treatment is used to remove the pectin component therein, and the cellulose is exposed and then treated with an organosilicon coupling agent. The organosilicon coupling agent can form a multi-site hydrogen bond coupling effect with the hydroxyl group of cellulose, thereby adsorbing on the cellulose surface, the purpose is to improve the compatibility of cellulose with the polylactic acid molecules modified by the polysiloxane segments, thereby further improving the mechanical properties, heat resistance and flame retardant properties of the environmentally friendly flame retardant material. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The scanning electron microscope (SEM) images of the cross-section of the polylactic acid-plant fiber environmentally friendly flame retardant material for the board prepared in Example 3 and Example 4 are shown. DETAILED DESCRIPTION

[0037] In conjunction with the embodiments of the present invention, the technical solutions in the embodiments are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] If the specific experimental conditions are not specified in the examples, they are usually based on the conventional conditions in the field or the conditions recommended by the reagent company; the materials, reagents, etc. used in the examples can be purchased through commercial channels unless otherwise specified.

[0039] The synthesis steps of the silicone coupling agent include: S1. Add 400g of propylene alcohol polyoxyethylene ether (APEG-400, Jiangsu Haian Petrochemical Plant) into a four-necked flask, and add 2g of inhibitor p-hydroxyanisole at the same time, dehydrate under reduced pressure at 100°C for 1 hour, then add 200mL of solvent toluene and 1g of reaction catalyst divinyltetramethyldisiloxane platinum complex IOTA-8100 (Anhui Aiyota Silicone Oil).

[0040] S2, under stirring, add 60.5g of hydrogenated silicone oil 1,3,5,7-tetramethylcyclotetrasiloxane (D4H) dissolved in 50mL toluene, and control the temperature of the reaction system to 90°C. Complete the addition of D4H and the solvent within 2 hours, and continue to maintain the temperature for 4 hours. After the reaction is completed, cool to 60°C and distill under reduced pressure to remove the solvent toluene.

[0041] S3. Continue to cool down to 40°C, slowly add 4.14 L of deionized water while stirring rapidly for emulsification, and continue stirring for 1 hour to obtain a light yellow emulsion, which is a 10 wt% organic silicone coupling agent aqueous solution.

[0042] Example 1 Place the cotton fiber on a flat vulcanizer and crush it through a cold pressing mode. Then use a fiber cutting machine to cut the cotton fiber into fibers with a length of 10 mm, put it into a container equipped with a stirring device, add the cut 10 mm fiber material and 10 wt% sodium hydroxide solution, stir at room temperature for 3 hours, take out the fiber material, wash it with clean water until the pH value of the water is neutral, add 10 wt% silicone coupling agent aqueous solution and stir at room temperature for 12 hours, filter out the fiber material and place it in a vacuum drying oven at 60°C and dry it for 8 hours.

[0043] Example 2 Place the sisal fiber on a flat vulcanizer and crush it by cold pressing mode. Then use a fiber cutting machine to cut the sisal fiber into fibers with a length of 15 mm, put it into a container equipped with a stirring device, add the cut 10 mm fiber material and 10 wt% sodium hydroxide solution, stir at room temperature for 4 hours, take out the fiber material, wash it with clean water until the pH value of the water is neutral, add 10 wt% silicone coupling agent aqueous solution and stir at room temperature for 15 hours, filter out the fiber material and place it in a vacuum drying oven at 60°C and dry it for 8 hours.

[0044] Example 3 The formula of polylactic acid-plant fiber environmentally friendly flame retardant material includes: polylactic acid 2500HP particles (NatureWorks LLC, USA), density 1.24g / cm 3, the melt flow rate is 8.0 g / 10min (test condition 210℃ / 2.16 kg), based on the mass of polylactic acid, the fiber material dosage of Example 1 is 30wt%, the modifier terminal carboxyl polydimethylsiloxane IOTA2520 (Anhui Aiyota silicone oil) is 8.5wt%, the flame retardant ammonium polyphosphate is 5wt%, the flame retardant monopentaerythritol is 2.5wt%, the flame retardant melamine is 1.5wt%, the cross-linking agent bisphenol A diallyl ether is 2.0wt%, and the nucleating agent ultrafine talc (talc through 8000 mesh sieve) is 1.5wt%.

[0045] The fiber material and polylactic acid are mixed on a two-roll plasticizer. The mixing is preheated for about half an hour before mixing, and mixing begins when the temperature rises to 185°C. After the polylactic acid particles are added between the two rollers and melted, when they are completely wrapped around the rollers, the formula amount of modifier, flame retardant, crosslinking agent and nucleating agent are added. After mixing evenly, the formula amount of fiber material is added and mixed again. When the material color is uniform, there is no obvious fiber material fragments that are not mixed evenly on the cross section, and the material has a clear gloss and a certain strength, the material on the roller is removed for molding.

[0046] The molding is carried out on a pressure molding machine. The temperature of the upper and lower heating plates is the same and both are set to 190°C. The pressure of the pressure molding machine is set to 12MPa. The molding time is 5min. At the same time, during the molding process, the metal mold containing the evenly mixed material is placed in the pressure molding machine and vacuumed to prevent bubbles. After the hot pressing is completed, the temperature is cooled to room temperature for cold pressing. After 15min of cold pressing, it is taken out of the mold for trimming.

[0047] The polylactic acid-plant fiber environmentally friendly flame retardant material after compression molding was used to prepare dumbbell-shaped specimens on an XJY-2 dumbbell punching machine, ready for the next test.

[0048] Example 4 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those of Example 3, except that the fiber material prepared in Example 2 is used.

[0049] Example 5 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the cross-linking agent is changed to 2,2'-diallyl bisphenol A, and the amount used is 2.0 wt%.

[0050] Example 6 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the fiber material prepared in Example 2 is used, and the amount of the fiber material used is 24 wt %.

[0051] Example 7 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the amount of the fiber material used is 36 wt %.

[0052] Example 8 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the modifier is epoxy-terminated polydimethylsiloxane (epoxy-terminated silicone oil) IOTA 105-1, and the dosage is 6.5wt%.

[0053] Example 9 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the modifier is terminal hydroxyl polydimethylsiloxane (terminal hydroxyl silicone oil) IOTA 2110, and the dosage is 10wt%.

[0054] Example 10 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the modifier is amino-terminated polydimethylsiloxane (amino-terminated silicone oil) Sivans ATS, and the dosage is 7.5wt%.

[0055] Comparative Example 1 The treatment steps for the cotton fiber are the same as those in Example 1, except that the fiber material is washed with clean water until the pH value of the water is neutral and then placed in a vacuum drying oven at 60° C. to dry for 8 hours, and no silicone coupling agent is used to treat the fiber material.

[0056] Comparative Example 2 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those of Example 3, except that the fiber material prepared in Comparative Example 1 is used.

[0057] Comparative Example 3 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that no modifier is used.

[0058] Comparative Example 4 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that the modifier is terminal side chain epoxy polydimethylsiloxane (terminal side chain epoxy silicone oil) IOTA 105-3, and the dosage is 6.5wt%.

[0059] Comparative Example 5 The formula and preparation method of the polylactic acid-plant fiber environmentally friendly flame retardant material are the same as those in Example 3, except that triallyl isocyanurate (TAIC) is used as a cross-linking agent in an amount of 2.0 wt %.

[0060] Performance test section Mechanical properties test: The tensile strength and elongation at break were tested according to standard ASTM-D638-2022, and the tensile test was carried out in a universal testing machine at a crosshead speed of 4 mm / min.

[0061] The flexural strength was tested according to standard ASTM D 790 using a universal testing machine at a crosshead speed of 1.3 mm / min.

[0062] The Izod notched impact strength was tested according to the standard ISO 180:2023, the test temperature was 23°C, the test humidity was 60%, and the Izod impact tester was used for testing. At least 8 tests were performed and the average value was taken as the final test data. The notch depth of the sample was 4mm.

[0063] Flame retardant performance test: According to the standard ISO 5660-1:2015, the polylactic acid-plant fiber environmentally friendly flame retardant material (100×100×3mm 3 ) to test, thereby obtaining the heat release rate (HRR), total heat release (THR) and ignition time (TTI), and calculating the flame retardant index (FRI) to evaluate its flame retardant performance. The calculation formula of FRI is shown in formula (1), wherein the calculation of the FRI value is based on the calculation result of Example 1, and the percentage of other embodiments and comparative examples relative to Example 1 is used as the corresponding FRI value. The higher the FRI value, the better the flame retardant performance of the environmentally friendly flame retardant material. Wherein T in formula (1) represents test, B represents basis, the THR×(HRR / TTI) result calculated in Example 1 is used as the basis, and the ratio of other embodiments and comparative examples to it is the test value.

[0064] .

[0065] Heat resistance test: The load deformation temperature of the polylactic acid-plant fiber environmentally friendly flame retardant material was tested according to the method of standard GB / T1634.1-2019 to evaluate its heat resistance. The mechanical properties and heat resistance of Examples 3-10 and Comparative Examples 1-5 are summarized in Table 1, and the flame retardant properties are summarized in Table 2.

[0066] Fracture surface SEM analysis: After the tensile test of the polylactic acid-plant fiber environmentally friendly flame retardant materials of Examples 3 and 4, the cross-section of the fractured specimens was tested by scanning electron microscopy (SEM). The results are as follows: Figure 1 shown.

[0067] Table 1:

[0068] Table 2:

[0069] The performance test results of Examples 3-10 and Comparative Examples 1-5 are shown in Tables 1 and 2. The present invention uses polydimethylsiloxane with terminal functional groups as a modifier for the polylactic acid composition, and the functional groups at both ends react with the polylactic acid molecular chain during high-temperature mixing, thereby reacting with the polylactic acid main chain and introducing polysiloxane segments, which have good softness and elasticity, can adapt to surfaces of different shapes and provide effective coverage, thereby improving the elongation at break and impact strength of the polylactic acid-plant fiber environmentally friendly flame retardant material, and at the same time, compared with the carbon-based main chain, the polysiloxane segment is more difficult to decompose at high temperature, thereby improving the load deformation temperature of the environmentally friendly flame retardant material. For plant fibers in environmentally friendly flame-retardant materials, basic alkaline treatment is used to remove the residual pectin components, and then the cellulose is exposed and treated with a silicone coupling agent. The silicone coupling agent has a cyclic silane core and multiple polyoxyethylene ether side chains, which can form multi-site hydrogen bond coupling with the hydroxyl groups of cellulose, thereby adsorbing on the cellulose surface. The purpose is to improve the compatibility of cellulose with polylactic acid molecules modified with polysiloxane segments, thereby further improving the mechanical properties, heat resistance and flame retardancy of environmentally friendly flame-retardant materials. Figure 1 The SEM test of the fracture surface of the polylactic acid-plant fiber environmentally friendly flame retardant material prepared in Examples 3 and 4 found that the plant fibers from different sources and the polylactic acid could be completely fused without obvious boundaries.

[0070] In addition, with regard to the selection of cross-linking agents in polylactic acid, Examples 3-10 of the present invention select difunctional bisphenol A diallyl ether or 2,2'-diallyl bisphenol A (DBA) to replace the commonly used trifunctional cross-linking agent triallyl isocyanurate (TAIC), thereby further improving the elongation at break and the impact strength of the polylactic acid-plant fiber environmentally friendly flame retardant material.

[0071] In Comparative Example 2, plant fibers that have not been treated with a silicone coupling agent are mixed with polylactic acid for compression molding. Terminally functionalized silicone oil is added to the polylactic acid to react with the main chain to introduce polysiloxane segments, resulting in poor compatibility between the polylactic acid-polysiloxane main chain and the plant fibers with strong polarity, thereby making the mechanical properties, heat resistance and flame retardant properties of the composite material of Comparative Example 2 poor.

[0072] Comparative Example 3 did not use end-functionalized silicone oil and did not introduce polysiloxane segments into the polylactic acid main chain, which was equivalent to using polylactic acid alone to mix with plant fibers. Since the polylactic acid main chain was not modified, the mechanical properties, heat resistance and flame retardant properties of the composite material of Comparative Example 3 were poor.

[0073] Comparative Example 4 uses end-side chain epoxy polydimethylsiloxane. Since there are also epoxy groups on the side chains that can be cross-linked with the carboxyl groups of the polylactic acid main chain, after high-temperature mixing, the end-side chain epoxy polydimethylsiloxane is equivalent to a cross-linking agent that simultaneously cross-links multiple polylactic acid main chains. Although the heat resistance and flame retardancy of the composite material of Comparative Example 4 are improved, its mechanical properties, especially the elongation at break and impact resistance, are significantly reduced.

[0074] Comparative Example 5 uses trifunctional TAIC to replace the difunctional crosslinking agent bisphenol A diallyl ether or 2,2'-diallyl bisphenol A to increase the crosslinking degree of polylactic acid after mixing, which also leads to a decrease in the elongation at break and impact resistance of the mechanical properties of the composite material of Comparative Example 5.

[0075] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to perform equivalent replacements on parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A polylactic acid composition, characterized in that The polylactic acid composition comprises: polylactic acid, a modifier, a flame retardant, a crosslinking agent and a nucleating agent; The modifier is a terminal functionalized polydimethylsiloxane, and terminal functionalization means that both ends of the linear polydimethylsiloxane have terminal functional groups, and the terminal functional groups include: carboxyl, hydroxyl, amino, and epoxy groups. At the same time, the side chains of the modifier molecules are all methyl groups, and no functional groups exist. The flame retardant includes a phosphorus flame retardant, a nitrogen flame retardant and a polyol, wherein the phosphorus flame retardant is selected from: any one or a combination of ammonium polyphosphate or organic phosphate; The nitrogen flame retardant is selected from any one or a combination of melamine, melamine cyanurate or dicyandiamide; The polyol is selected from: any one or a combination of monopentaerythritol, dipentaerythritol, trimethylolpropane or trimethylolethane; The crosslinking agent is selected from a diene crosslinking agent containing a bisphenol A core; The nucleating agent is selected from talc.

2. The polylactic acid composition according to claim 1, characterized in that The polylactic acid composition is based on the mass of polylactic acid, and the amount of the modifier is 1-15wt%; The dosage of flame retardant is 1~15wt%; The amount of cross-linking agent is 1~5wt%; The dosage of nucleating agent is 0.5~5wt%.

3. A polylactic acid-plant fiber environmentally friendly flame retardant material for a board, characterized in that: The environmentally friendly flame retardant material comprises: the polylactic acid composition and plant fiber as described in any one of claims 1 to 2; Wherein, the plant fiber is selected from any one of cotton fiber, hemp fiber and wood fiber; The length of plant fibers is 5~15mm; The plant fiber is firstly treated with alkali and then treated with an aqueous solution of an organic silicon coupling agent, wherein the organic silicon coupling agent is a linear or cyclic polysiloxane grafted with a polyoxyethylene ether chain segment.

4. The polylactic acid-plant fiber environmentally friendly flame retardant material for plates according to claim 3, characterized in that: The alkali treatment is to soak the plant fibers in a sodium hydroxide solution, then wash them until the pH is neutral, and then dry them; the organic silicon coupling agent aqueous solution treatment is to soak the plant fibers after the alkali treatment in an organic silicon coupling agent aqueous solution.

5. The method for preparing the polylactic acid-plant fiber environmentally friendly flame retardant material for plates according to any one of claims 3 to 4, characterized in that: The preparation method comprises: mixing and molding, wherein the mixing specifically comprises: melting and mixing polylactic acid, a modifier, a flame retardant, a cross-linking agent and a nucleating agent on a plasticizer, and then adding plant fibers for mixing; wherein the mixing temperature is higher than the melting point of the polylactic acid; The compression molding includes: compression molding the mixed material at a temperature of 175-210° C. and a pressure of 10-20 MPa.

6. The preparation method according to claim 5, characterized in that: After the compression molding is completed, the temperature continues to drop to room temperature for cold pressing, and the cold pressing time is 10 to 30 minutes.

7. Use of the polylactic acid-plant fiber environmentally friendly flame retardant material for panels as described in any one of claims 3 to 4 in automotive interior trim panels, lighting decorative panels, and automotive partition composite panels.

8. A high-toughness flame-retardant interior panel, characterized in that: The high-toughness flame-retardant interior panel is prepared from the polylactic acid-plant fiber environmentally friendly flame-retardant material according to any one of claims 3-4.

9. A flame retardant partition composite panel, characterized in that: The flame-retardant partition composite plate is prepared from the polylactic acid-plant fiber environmentally friendly flame-retardant material according to any one of claims 3-4.

10. A motorhome, comprising at least one of the high-toughness flame-retardant interior panel according to claim 8 and the flame-retardant partition composite panel according to claim 9.

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