High-strength and high-toughness phb plant fiber composite material and preparation method thereof

Abstract

The application relates to the technical field of high polymer composite materials, and more specifically relates to a high-strength and high-toughness PHA plant fiber composite material and a preparation method thereof.A high-strength and high-toughness PHA plant fiber composite material comprises the following raw materials in parts by mass: 60-80 parts of polyhydroxyalkanoate, 20-30 parts of modified palm fiber, 1-5 parts of a plasticizer and 2-4 parts of a nucleating agent, wherein the modified palm fiber is palm fiber modified by long-chain fatty acid.The PHA plant fiber composite material has excellent strength and toughness, excellent ultraviolet resistance and excellent degradability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer composite materials, and more particularly to a high-strength and high-toughness PHA plant fiber composite material and a preparation method thereof. BACKGROUND

[0002] PHA, also known as polyhydroxyalkanoate, is a kind of bio-based polymer material synthesized by microorganisms in a nutrient-rich environment. It has excellent biodegradability and can be completely degraded by microorganisms into titanium dioxide and water in the natural environment, thereby avoiding the problem of accumulation of traditional plastics in the environment. At the same time, PHA also has good plasticity and thermoplasticity and can be molded through processes such as injection molding, extrusion and blow molding.

[0003] However, the mechanical properties of PHA are poor, even lower than those of other degradable materials such as polylactic acid, so the toughening and reinforcement of PHA are the top priority in the field of PHA research. At present, the toughening and reinforcement of PHA are carried out by using fiber reinforcement, and compared with synthetic fibers, plant fibers not only have excellent toughening and reinforcement effect, but also can be degraded under the action of microorganisms, thereby not affecting the degradability of PHA.

[0004] However, there are a large number of hydroxyl groups on the surface of plant fibers, which have strong hydrophilicity, and PHA molecules are low-polarity materials. This polarity leads to difficulty in uniform mixing of plant fibers and PHA materials when they are blended, that is, there is an interface, which further leads to the mechanical properties of the prepared PHA plant fiber composite material still having room for improvement. SUMMARY

[0005] In order to improve the defect that the plant fibers and PHA are difficult to mix uniformly in the conventional PHA plant fiber composite material, the present application provides a high-strength and high-toughness PHA plant fiber composite material and a preparation method thereof.

[0006] In a first aspect, the present application provides a high-strength and high-toughness PHA plant fiber composite material, which adopts the following technical solution:

[0007] A high-strength and high-toughness PHA plant fiber composite material, comprising the following raw materials by mass: 60-80 parts of polyhydroxyalkanoate, 20-30 parts of modified palm fiber and 2-4 parts of lubricant, wherein the modified palm fiber is a long-chain fatty acid modified palm fiber.

[0008] The cellulose of palm fiber is relatively long, so it has excellent strength and toughness, but there are a large number of hydroxyl groups on the surface of palm fiber, and the palm fiber also has a high degree of intramolecular hydrogen bond, which makes the interface wettability and adhesion between palm fiber and PHA very poor.

[0009] And after the modification of long chain fatty acid, the carboxyl in long chain fatty acid reacts with the hydroxyl on the surface of palm fiber under the catalysis of catalyst, esterification reaction, in the consumption of hydroxyl, also can connect long chain fatty acid on the surface of palm fiber and form ester, thus obtains extremely excellent compatibility with polyhydroxyalkanoate, reduces the interface, promotes the PHA plant fiber composite material to obtain more excellent strength and toughness.

[0010] Preferably, the preparation method of the modified palm fiber comprises the following steps:

[0011] S1, first wash the palm long fiber with deionized water for 3-5 times, dry at 30-50℃ and cut, the length of palm fiber is 5-10mm;

[0012] S2, soak the palm fiber in deionized water, then add potassium hydroxide solution, continue stirring for 2-4h, then dry the palm fiber, get the alkaline palm fiber;

[0013] S3, add long chain fatty acid and stannous oxalate to the alkaline palm fiber, stir evenly, then react at 80-90℃ for 4-8h, then cool to room temperature, finally wash and dry, get the modified palm fiber.

[0014] Preferably, the preparation method of the modified palm fiber comprises the following steps:

[0015] S1, first wash the palm long fiber with deionized water for 3-5 times, dry at 30-50℃ and cut, the length of palm fiber is 5-10mm;

[0016] S2, soak 6-10g palm fiber in 80-90ml deionized water, then add 1-3ml 25wt% potassium hydroxide solution, continue stirring for 2-4h, then dry the palm fiber, get the alkaline palm fiber;

[0017] S3, add 2-4g long chain fatty acid and 0.2-0.4g stannous oxalate to the alkaline palm fiber, stir evenly, then react at 80-90℃ for 4-8h, then cool to room temperature, finally wash and dry, get the modified palm fiber.

[0018] When the adding amount of each component of the modified palm fiber is as above, the content of hydroxyl on the surface of palm fiber will be relatively less, at the same time, more long chain fatty acid ester will be attached to the surface of palm fiber, thus the compatibility of palm fiber and polyhydroxyalkanoate is more excellent, the PHA plant fiber composite material obtains more excellent strength and toughness.

[0019] Preferably, in S3, nano titanium dioxide is also added.

[0020] When the PHA plant fiber composite material is exposed to strong ultraviolet light, the ultraviolet light will excite the chemical bonds in the PHA to form free radicals, causing the PHA molecular chain to break, and further causing the PHA plant fiber composite material to be oxidatively degraded, but this degradation causes the PHA plant fiber composite material to be easily degraded unnecessarily during actual use, resulting in a shorter service life of the PHA plant fiber composite material.

[0021] The nano-titanium dioxide can absorb and reflect ultraviolet light, and can also eliminate the generation of free radicals. Meanwhile, the palm fiber surface contains a large number of pores, which can effectively load the nano-titanium dioxide, thereby effectively improving the ultraviolet resistance performance of the PHA plant fiber composite material.

[0022] Preferably, the step S3 is:

[0023] 2-4 g of long-chain fatty acid and 0.2-0.4 g of stannous oxalate are added to the basic palm fiber, stirred uniformly, then reacted at 80-90°C for 4-8 h, then 1-2 g of nano-titanium dioxide is added, stirred again for 30-60 min, then cooled to room temperature, and finally washed and dried to obtain the modified palm fiber.

[0024] Preferably, in the step S3, the nano-titanium dioxide is first modified by vinyltriethoxysilane, and the long-chain fatty acid is unsaturated long-chain fatty acid DPA-FITC.

[0025] Although the palm fiber can load the nano-titanium dioxide through the pores, pure physical adsorption loading may still cause the nano-titanium dioxide to detach and agglomerate, thereby affecting the ultraviolet resistance performance of the PHA plant fiber composite material.

[0026] When the nano-titanium dioxide is first modified by vinyltriethoxysilane, the double bonds in the vinyltriethoxysilane recombine with the double bonds in the unsaturated long-chain fatty acid, thereby facilitating the nano-titanium dioxide to be connected to the matrix of the PHA plant fiber composite material, further reducing the possibility of the nano-titanium dioxide detaching, effectively improving the dispersibility of the nano-titanium dioxide in the PHA plant fiber composite material, and indirectly improving the ultraviolet resistance performance of the PHA plant fiber composite material.

[0027] Preferably, the mass ratio of the vinyltriethoxysilane to the nano-titanium dioxide is 1: (1:3).

[0028] When the vinyltriethoxysilane and the nano-titanium dioxide are in the above mass ratio, the prepared PHA plant fiber composite material will have more excellent ultraviolet resistance performance.

[0029] Preferably, the step S3 is:

[0030] 2-4g long-chain fatty acid and 0.2-0.4g stannous oxalate are added to the alkaline palm fiber, stirred uniformly, and then reacted at 80-90℃ for 4-8h, after which the nano-titanium dioxide modified by vinyl triethoxysilane is added, the nano-titanium dioxide is added in an amount of 1-3g, 0.2-0.4g azobisisobutyronitrile is added at the same time, and mixed and stirred at 70-90℃ for 1-2h, after which 0.2-0.4g triethylamine is added for neutralization, cooled to room temperature, and finally washed and dried to obtain the modified palm fiber.

[0031] In a second aspect, the application provides a preparation method of a high-strength and high-toughness PHA plant fiber composite material, which adopts the following technical scheme:

[0032] A preparation method of a high-strength and high-toughness PHA plant fiber composite material, comprising the following steps:

[0033] Step one, first dry the polyhydroxyalkanoate powder at a temperature of 70-80℃, and control the water content of the polyhydroxyalkanoate to be less than 30PPM;

[0034] Step two, mix the polyhydroxyalkanoate powder, the modified palm fiber and the lubricant, and then transfer them to a twin-screw extruder for melt extrusion and drying to obtain the high-strength and high-toughness PHA plant fiber composite material;

[0035] The parameters of the twin-screw extruder are as follows: the melt temperature is 180-190℃, and the screw rotation speed is 200-400r / min.

[0036] In summary, the application has the following beneficial effects:

[0037] 1. The cellulose of palm fiber is relatively long, so it has excellent strength and toughness, but there are a large number of hydroxyl groups on the surface of palm fiber, and the palm fiber also has a high degree of intramolecular hydrogen bond, which makes the interface wettability and adhesion between palm fiber and PHA very poor;

[0038] After modification by long-chain fatty acid, the carboxyl group in the long-chain fatty acid reacts with the hydroxyl group on the surface of the palm fiber under the action of the catalyst to form ester, which can connect the long-chain fatty acid to the surface of the palm fiber and obtain excellent compatibility with polyhydroxyalkanoate, reduce the interface, and promote the PHA plant fiber composite material to obtain more excellent strength and toughness.

[0039] 2、When the PHA plant fiber composite material is exposed to strong ultraviolet light, the ultraviolet light will excite the chemical bonds in the PHA to form free radicals, causing the PHA molecular chain to break, and further causing the PHA plant fiber composite material to be oxidatively degraded, but this degradation causes the PHA plant fiber composite material to be easily degraded unnecessarily during actual use, resulting in a shorter service life of the PHA plant fiber composite material;

[0040] The nano-titanium dioxide can absorb and reflect ultraviolet light, and at the same time eliminate the generation of free radicals. Meanwhile, the palm fiber surface contains a large number of pores, which can effectively load the nano-titanium dioxide, thereby effectively improving the ultraviolet resistance performance of the PHA plant fiber composite material.

[0041] 3、Although the palm fiber can load the nano-titanium dioxide through the pores, the physical adsorption loading may still cause the nano-titanium dioxide to separate and agglomerate, thereby affecting the ultraviolet resistance performance of the PHA plant fiber composite material;

[0042] When the nano-titanium dioxide is first modified by vinyl triethoxysilane, the double bonds in the vinyl triethoxysilane and the double bonds in the unsaturated long-chain fatty acid recombine, thereby enabling the nano-titanium dioxide bond to be connected to the matrix of the PHA plant fiber composite material, further reducing the possibility of the nano-titanium dioxide separating, effectively improving the dispersibility of the nano-titanium dioxide in the PHA plant fiber composite material, and indirectly improving the ultraviolet resistance performance of the PHA plant fiber composite material. DETAILED DESCRIPTION

[0043] The present application will be further described in detail below in combination with Examples 1-8 and Comparative Example 1.

[0044] Raw materials

[0045] Polyhydroxyalkanoate Lanbai; palm fiber Conventional commercially available; lubricant Calcium stearate CAS: 1592-23-0; unsaturated long-chain fatty acid DPA-FITC Xinweichuang; potassium hydroxide CAS: 1310-58-3;

[0046] Stannous oxalate CAS: 814-94-8; nano-titanium dioxide CAS: 13463-67-7; vinyl triethoxysilane CAS: 78-08-0; long-chain saturated fatty acid-stearic acid CAS: 57-11-4.

[0047] Example 1

[0048] A high-strength and high-toughness PHA plant fiber composite material, comprising the following amounts of raw materials: 70 g of polyhydroxyalkanoate, 25 g of modified palm fiber, and 3 g of lubricant, the modified palm fiber being long-chain fatty acid modified palm fiber.

[0049] The preparation method of the modified palm fiber comprises the following steps:

[0050] S1, first, the palm long fiber 4 is washed with deionized water, dried at a temperature of 50°C and cut, and the length of the palm fiber is 8mm;

[0051] S2, 8g of palm fiber is soaked in 90ml of deionized water, then 2ml of 25wt% potassium hydroxide solution is added, stirring is continued for 3h, and then the palm fiber is dried to obtain the alkaline palm fiber;

[0052] S3, 3g of unsaturated long-chain fatty acid DPA-FITC and 0.3g of stannous oxalate are added to the alkaline palm fiber, stirred uniformly, then reacted at 90°C for 6h, then cooled to room temperature, and finally washed and dried to obtain the modified palm fiber.

[0053] The preparation method of the high-strength and high-toughness PHA plant fiber composite material comprises the following steps:

[0054] Step one, first, the polyhydroxyalkanoate powder is dried at a temperature of 70-80°C, and the water content of the polyhydroxyalkanoate is controlled to be less than 30PPM;

[0055] Step two, the polyhydroxyalkanoate powder, the modified palm fiber and the lubricant are mixed, then transferred to a twin-screw extruder for melt extrusion and drying to obtain the high-strength and high-toughness PHA plant fiber composite material;

[0056] Wherein, the parameters of the twin-screw extruder are as follows: the melting temperature is 190°C, and the screw rotation speed is 400r / min.

[0057] Example 2-3

[0058] The difference from example 1 is that the addition amount of each component in the modified palm fiber is different, as shown in Table 1.

[0059] Table 1 Addition amount table of each component in the modified palm fiber in example 1 and example 2-3

[0060] Example 1 Example 2 Example 3 Palm fibres 8g 6g 10g 25 wt% potassium hydroxide solution 2ml 3ml 1ml Unsaturated long chain fatty acid 3g 2g 4g

[0061] Example 4

[0062] The difference from example 1 is that in S3, nano titanium dioxide is also added;

[0063] The steps of S3 are:

[0064] To the alkaline palm fiber, 3g of unsaturated long-chain fatty acid DPA-FITC and 0.3g of stannous oxalate are added, stirred uniformly, then reacted at 90°C for 6h, then 1.5g of nano titanium dioxide is added, stirred again for 45min, then cooled to room temperature, and finally washed and dried to obtain modified palm fiber.

[0065] The difference from Example 4 is that the nano titanium dioxide is first modified by vinyl triethoxysilane;

[0066] The steps of S3 are:

[0067] To the alkaline palm fiber, 3g of unsaturated long-chain fatty acid DPA-FITC and 0.3g of stannous oxalate are added, stirred uniformly, then reacted at 90°C for 6h, then 1.5g of nano titanium dioxide is added, stirred again for 45min, then cooled to room temperature, and finally washed and dried to obtain modified palm fiber.

[0068] The difference from Example 5 is that the mass ratio of vinyl triethoxysilane to nano titanium dioxide is different, as shown in Table 2.

[0069] Examples 5-7

[0070] Table 2 Mass ratio of vinyl triethoxysilane to nano titanium dioxide in Examples 5-7

[0071] Example 5 Example 6 Example 7 Vinyltriethoxysilane 1 1 1 Nano titanium dioxide 2 1 3

[0072] Example 8

[0073] The difference from Example 1 is that the unsaturated long-chain fatty acid DPA-FITC is replaced by saturated long-chain fatty acid-stearic acid.

[0074] Comparative Example 1

[0075] A PHA plant fiber composite material includes the following mass of raw materials: 70g of polyhydroxyalkanoate and 3g of lubricant.

[0076] The preparation method of the PHA plant fiber composite material includes the following steps:

[0077] Step one, first dry the polyhydroxyalkanoate powder at a temperature of 70-80°C, control the water content of the polyhydroxyalkanoate to be less than 30PPM;

[0078] Step two, mixing the polyhydroxyalkanoate powder and lubricant, then transferring to a twin-screw extruder for melt extrusion and drying to obtain a high-strength and high-toughness PHA plant fiber composite material;

[0079] The parameters of the twin-screw extruder are as follows: melting temperature 190℃, screw rotation speed 400r / min.

[0080] Performance test

[0081] I. Tensile strength test

[0082] Three samples were taken from each of Examples 1-3 and Comparative Example 1, and then the tensile strength of the samples was tested according to GB / T1040-2024 "Plastics - Determination of tensile properties", and the average value was taken, and the test data are shown in Table 3.

[0083] Table 3 Tensile strength of Examples 1-3 and Comparative Example 1

[0084] Tensile strength / MPa Tensile strength / MPa Example 1 79 Example 3 76 Example 2 74 Comparative Example 1 54

[0085] II. Anti-ultraviolet performance test

[0086] Six samples were taken from each of Example 1 and Examples 4-8, and then the tensile strength of three of them was tested according to GB / T1040-2024 "Plastics - Determination of tensile properties", and the average value was taken, and recorded as the original tensile strength;

[0087] Then, the remaining three samples were treated with ultraviolet light according to the fluorescent ultraviolet light exposure test method of GB / T 14522-2008 "Artificial weathering test methods of plastics, coatings, and rubber materials for mechanical industry products - Fluorescent ultraviolet lamps", with an irradiation intensity of 0.68W / m2×nm, continuous light for 700h, blackboard temperature of 63℃, no spraying condition, and finally the tensile strength of the three samples after aging was tested again according to GB / T1040-2024 "Plastics - Determination of tensile properties", and the average value was taken, and recorded as the aged tensile strength;

[0088] Finally, the anti-ultraviolet rate was calculated, anti-ultraviolet rate = aged tensile strength / original tensile strength × 100%, and the test data are shown in Table 4.

[0089] Table 4 Anti-ultraviolet performance of Example 1 and Examples 4-8 / %

[0090] UV resistance UV resistance Example 1 53.7% Example 6 90.1% Example 4 85.6% Example 7 91.3% Example 5 93.9% Example 8 88.5%

[0091] It can be seen from the reference example 1 and the comparative example 1 and in combination with Table 3 that the tensile strength of the example 1 is significantly improved compared with the comparative example 1, thus indicating that after the surface of the palm fiber is modified by the unsaturated long-chain fatty acid DPA-FITC, the mechanical property of the PHA plant fiber composite prepared will be significantly improved.

[0092] The reason is that the cellulose of the palm fiber is relatively long, thus the palm fiber has excellent strength and toughness, but there are a large number of hydroxyl groups on the surface of the palm fiber, and the palm fiber also has a high degree of intramolecular hydrogen bond, which makes the interface wettability and adhesion between the palm fiber and the PHA very poor.

[0093] After the modification of the long-chain fatty acid, the carboxyl group in the long-chain fatty acid reacts with the hydroxyl group on the surface of the palm fiber under the action of the catalyst to form esterification, which consumes the hydroxyl group and connects the long-chain fatty acid to the surface of the palm fiber to form ester, thus obtaining excellent compatibility with the polyhydroxyalkanoate, reducing the interface, and promoting the PHA plant fiber composite to obtain more excellent strength and toughness.

[0094] It can be seen from the reference example 1-3 and in combination with Table 3 that the tensile strength of the examples 2-3 is slightly decreased compared with the example 1, thus indicating that when the components in the modified palm fiber are added in the amount of the example 1, the PHA plant fiber composite prepared will have more excellent mechanical property.

[0095] It can be seen from the reference example 1 and the example 4 and in combination with Table 4 that the ultraviolet resistance of the example 4 is significantly improved compared with the example 1, thus indicating that the addition of the nano titanium dioxide can effectively improve the ultraviolet resistance of the PHA plant composite.

[0096] The reason is that when the PHA plant fiber composite is exposed to strong ultraviolet light, the ultraviolet light will excite the chemical bond in the PHA to form free radicals, thus causing the PHA molecular chain to break, and further causing the PHA plant fiber composite to be oxidatively degraded, but this degradation causes the PHA plant fiber composite to be easily degraded unnecessarily in the actual use process, thus causing the service life of the PHA plant fiber composite to be short.

[0097] The nano titanium dioxide can absorb and reflect ultraviolet light, and can also eliminate the generation of free radicals, and the surface of the palm fiber contains a large number of pores, which can effectively load the nano titanium dioxide, thus effectively improving the ultraviolet resistance of the PHA plant fiber composite.

[0098] It can be seen from the reference to the embodiment 4 and the embodiment 5 and in combination with the table 4 that the anti-ultraviolet rate of the embodiment 5 is further improved compared with the embodiment 4, thereby indicating that the operation of modifying the nano-titanium dioxide by the vinyl triethoxysilane can further improve the anti-ultraviolet performance of the PHA plant composite material.

[0099] The reason is that although the palm fiber can load the nano-titanium dioxide through the hole, the pure physical adsorption loading can still cause the nano-titanium dioxide to be separated and aggregated, thereby affecting the anti-ultraviolet performance of the PHA plant fiber composite material.

[0100] When the nano-titanium dioxide is first modified by the vinyl triethoxysilane, the double bond in the vinyl triethoxysilane recombines with the double bond in the unsaturated long-chain fatty acid, thereby promoting the nano-titanium dioxide to be connected to the matrix of the PHA plant fiber composite material, further reducing the possibility of the nano-titanium dioxide being separated, effectively improving the dispersibility of the nano-titanium dioxide in the PHA plant fiber composite material, and indirectly improving the anti-ultraviolet performance of the PHA plant fiber composite material.

[0101] It can be seen from the reference to the embodiment 5-7 and in combination with the table 4 that the anti-ultraviolet rates of the embodiments 6-7 are slightly decreased compared with the embodiment 5, thereby indicating that when the mass ratio of the vinyl triethoxysilane to the nano-titanium dioxide is the mass ratio of the embodiment 5, the PHA plant composite material prepared will have more excellent anti-ultraviolet performance.

[0102] It can be seen from the reference to the embodiment 5 and the embodiment 8 and in combination with the table 4 that the anti-ultraviolet rate of the embodiment 8 is obviously decreased compared with the embodiment 5, thereby indicating that compared with the unsaturated long-chain fatty acid, the selection of the saturated long-chain fatty acid will cause the dispersibility of the nano-titanium dioxide and the PHA plant fiber composite material to be obviously decreased, the reason is that the long chain of the saturated long-chain fatty acid no longer has a double bond, the nano-titanium dioxide is only connected to the palm fiber through the silane coupling effect of the vinyl triethoxysilane, the connection effect is relatively insufficient, the nano-titanium dioxide is relatively more likely to be separated and the dispersibility is relatively more insufficient, and finally the anti-ultraviolet performance of the PHA plant fiber composite material is slightly decreased.

[0103] The specific embodiment is only an explanation of the present application, which is not a limitation of the present application, and those skilled in the art can make modifications to the present embodiment without creative contribution after reading the present specification, but as long as the present application is within the scope of the claims, it is protected by the patent law.

Claims

1. A high-strength high-toughness PHA plant fiber composite material, characterized by, The raw materials include the following quality parts: 60-80 parts of polyhydroxyaliphatic acid ester, 20-30 parts of modified palm fiber and 2-4 parts of lubricant, wherein the modified palm fiber is palm fiber modified by long-chain fatty acid; The preparation method of the modified palm fiber comprises the following steps: S1, first, the palm long fiber is washed with deionized water for 3-5 times, dried at a temperature of 30-50 DEG C and cut, and the length of the palm fiber is 5-10 mm; S2, the palm fiber is soaked in deionized water, then potassium hydroxide solution is added, stirring is continued for 2-4 h, and then the palm fiber is dried to obtain alkaline palm fiber; S3, 2-4 g of long-chain fatty acid and 0.2-0.4 g of stannous oxalate are added to the alkaline palm fiber, stirring is uniform, then reaction is carried out at 80-90 DEG C for 4-8 h, then nano-titanium dioxide modified by vinyl triethoxysilane is added, the addition amount of nano-titanium dioxide is 1-3 g, 0.2-0.4 g of azobisisobutyronitrile is added at the same time, mixing and stirring are carried out at 70-90 DEG C for 1-2 h, then 0.2-0.4 g of triethylamine is added for neutralization, cooling is carried out to room temperature, finally washing and drying are carried out to obtain modified palm fiber; The nano-titanium dioxide is first modified by vinyl triethoxysilane, and the long-chain fatty acid is unsaturated long-chain fatty acid DPA-FITC.

2. The high strength high toughness PHA plant fiber composite material according to claim 1, characterized in that, The preparation method of the modified palm fiber comprises the following steps: S1, first, the palm long fiber is washed with deionized water for 3-5 times, dried at a temperature of 30-50 DEG C and cut, and the length of the palm fiber is 5-10 mm; S2, 6-10 g of palm fiber is soaked in 80-90 ml of deionized water, then 1-3 ml of 25 wt% potassium hydroxide solution is added, stirring is continued for 2-4 h, and then the palm fiber is dried to obtain alkaline palm fiber; S3, 2-4 g of long-chain fatty acid and 0.2-0.4 g of stannous oxalate are added to the alkaline palm fiber, stirring is uniform, then reaction is carried out at 80-90 DEG C for 4-8 h, then nano-titanium dioxide modified by vinyl triethoxysilane is added, the addition amount of nano-titanium dioxide is 1-3 g, 0.2-0.4 g of azobisisobutyronitrile is added at the same time, mixing and stirring are carried out at 70-90 DEG C for 1-2 h, then 0.2-0.4 g of triethylamine is added for neutralization, cooling is carried out to room temperature, finally washing and drying are carried out to obtain modified palm fiber; The nano-titanium dioxide is first modified by vinyl triethoxysilane, and the long-chain fatty acid is unsaturated long-chain fatty acid DPA-FITC.

3. The high strength high toughness PHA plant fiber composite material according to claim 1, characterized in that The mass ratio of the vinyl triethoxysilane to the nano-titanium dioxide is 1: (1:3).

4. A method for preparing the high-strength and high-toughness PHA plant fiber composite material according to any one of claims 1 to 3, characterized by, The preparation method comprises the following steps: Step one, first, the polyhydroxyaliphatic acid ester powder is dried at a temperature of 70-80 DEG C, and the water content of the polyhydroxyaliphatic acid ester is controlled to be less than 30 PPM; Step two, the polyhydroxyaliphatic acid ester powder, the modified palm fiber and the lubricant are mixed, then transferred to a double-screw extruder for melt extrusion and drying to obtain a high-strength and high-toughness PHA plant fiber composite material; The parameters of the double-screw extruder are as follows: the melting temperature is 180-190 DEG C, and the screw rotation speed is 200-400 r / min.