Biochar-based toughening composite material for PLA (polylactic acid) and preparation method of biochar-based toughening composite material

Abstract

The invention relates to the technical field of material preparation, in particular to a biochar-based toughening composite material for PLA (polylactic acid) and a preparation method of the biochar-based toughening composite material. The composite material is prepared from biochar and a methyl methacrylate polymer, the mass ratio of the biochar to the methyl methacrylate polymer is 2: 5. According to the invention, the characteristic of good compatibility of MMA and biodegradable resin is utilized, and the problem of incompatibility of biochar and biodegradable resin is effectively solved through a method of constructing a soft phase (MMA unit) on the surface of a hard phase (biochar); the biochar-based toughening composite material prepared by the invention can effectively improve the mechanical property and thermal stability of biodegradable resin, expands the application field of the biodegradable resin, improves the durability of the biodegradable resin, and enhances the application competitiveness of the biodegradable resin with petroleum-based materials.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to a biochar-based toughened composite material for PLA and a preparation method thereof. Background Art

[0002] Biodegradable plastics are widely used in packaging, medicine and automotive engineering due to their good environmental friendliness and biocompatibility. However, their brittleness, low stability and high cost limit their application in a wider range of fields.

[0003] As a renewable resource, biochar is low-cost and widely available. It can be used to modify biodegradable resins, making them have high mechanical properties, improving thermal properties, preparing environmentally friendly materials, and accelerating biodegradation of materials. However, the poor dispersibility of biochar in biodegradable resins, obvious interface defects, and reduced thermal stability of materials have greatly limited the application of biochar in the preparation of environmentally friendly materials. Summary of the invention

[0004] In order to improve the poor dispersibility and interface defect problems of biochar in biodegradable resin, the present invention provides a biochar-based toughened composite material for PLA and a preparation method thereof, with biochar as a hard phase and methyl methacrylate polymer (MMA unit) as a soft phase, for improving the mechanics, thermal stability and crystallinity of biodegradable resin. The biochar-based toughened composite material prepared by the method can regulate the mechanics, thermal stability and crystallinity of biodegradable resin by adjusting the biochar preparation temperature and the biochar particle size, and can be applied to 3D printing.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] On one hand, the present invention provides a biochar-based toughened composite material for PLA, wherein the composite material consists of biochar and methyl methacrylate polymer; the mass ratio of the biochar to the methyl methacrylate polymer is 2:5.

[0007] In the above technical solution, further, the biochar includes one or a combination of multiple types of Pinus sylvestris charcoal, rice husk charcoal, fallen leaf charcoal, and straw charcoal.

[0008] In the above technical solution, further, the preparation temperature of the biochar is 350-750°C.

[0009] Another aspect of the present invention provides a method for preparing the biochar-based toughened composite material for PLA, the method comprising the following steps:

[0010] (1) preparing biochar into biochar powder by ball milling;

[0011] (2) dispersing biochar powder into a reaction solvent;

[0012] (3) Adding a catalyst to a uniformly dispersed biochar solution in a nitrogen atmosphere, and continuously heating and stirring until the temperature reaches a preset temperature, then adding methyl methacrylate monomer in a dropwise manner for reaction, washing, centrifuging, and drying to obtain the biochar-based toughened composite material.

[0013] In the above technical solution, further, in step (1), the ball milling uses a planetary ball mill, the ball milling speed is 200-350r / min, and the ball milling time is 0.1-2.5h, and more preferably, the ball milling speed is 300r / min, and the ball milling time is 2.5h;

[0014] The particle size of the biochar powder is 0.5 μm-70 μm.

[0015] In the above technical solution, further, in step (2), the reaction solvent is a mixed solution of one or more of methanol, ethanol and deionized water, and more preferably, the reaction solvent is ethanol:deionized water = 75wt%:25wt%.

[0016] In the above technical solution, further, in step (3), the catalyst is one of azobisisobutyronitrile (AIBN) and sodium dodecyl sulfate (SDS), and more preferably, the catalyst is azobisisobutyronitrile; the amount of catalyst added accounts for 0.1%-1% of the mass of methyl methacrylate monomer.

[0017] In the above technical solution, further, in step (3), the stirring speed is 370r / min and the stirring temperature is 80-90°C.

[0018] In the above technical solution, further, in step (3), the preset temperature is 60-100° C., and the reaction time is 2-10 h.

[0019] In the above technical solution, further, in step (3), the dropping speed of the methyl methacrylate monomer is 0.1-10 mL / min.

[0020] The washing solution is a combination of one or more of methanol, ethanol and deionized water. More preferably, the washing solution is ethanol: deionized water = 70wt%: 30wt%;

[0021] The centrifugal speed is 3000-4200r / min;

[0022] The drying temperature is 40-70° C., and the drying time is 4-12 hours.

[0023] The present invention utilizes the good compatibility of MMA and biodegradable resins, and effectively solves the problem of incompatibility between biochar and biodegradable resins by constructing a soft phase (MMA unit) on the surface of a hard phase (biochar). The prepared biochar-based reinforced material effectively improves the mechanical properties, thermal stability and crystallization ability of the biodegradable resin. Through the above method, while reducing the cost of reinforcing biodegradable resins, it reduces the disposal problem of waste materials and reduces dependence on fossil fuels, which is in line with the principle of sustainable development.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] (1) The biochar-based toughened composite material prepared by the present invention can effectively improve the mechanical properties and thermal stability of biodegradable resins, expand the application field of biodegradable resins, improve their durability, and enhance their application competitiveness with petroleum-based materials.

[0026] (2) The biochar-based toughened composite material prepared by the present invention reduces the preparation cost of environmentally friendly materials. The raw materials of biochar are usually agricultural waste or wood waste, and its production cost is relatively low. Compared with some expensive synthetic materials, biochar can effectively reduce production costs. The cost of MMA is relatively stable and widely used. By rationally mixing MMA, the cost can be controlled while improving the performance of the resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The cross-sectional structures of the PLA strips prepared in Comparative Example 1 and Example 1, a is Comparative Example 1, and b is Example 1;

[0028] Figure 2 The tensile strength and flexural strength test results of the PLA strips prepared under different CP addition conditions in Example 1, a is the tensile strength, and b is the flexural strength;

[0029] Figure 3 The crystallization of PLA strips prepared under different CP addition conditions in Example 1;

[0030] Figure 4 The tensile strength and flexural strength test results of PLA specimens prepared at different biochar preparation temperatures in Examples 1-3, a is the tensile strength, b is the flexural strength;

[0031] Figure 5 The tensile strength and bending strength test results of the PLA strips prepared in Example 1, Example 4 and Example 5, a is the tensile strength, and b is the bending strength;

[0032] Figure 6The tensile strength and flexural strength of the PLA strips prepared in Example 6 and Example 7, a is the tensile strength, and b is the flexural strength. DETAILED DESCRIPTION

[0033] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. In order to better illustrate the purpose of the present invention and the advantages of the technical solution, specific examples are used below for further explanation, but the protection scope of the present invention is not limited to the following examples.

[0034] Comparative Example 1

[0035] Pinus sylvestris charcoal (PS) was prepared by thermal cracking of Pinus sylvestris var. mongolica at 550°C in a tube furnace. The PS was dried at 60°C for 10 h, poured into a planetary ball mill, and ball-milled at 350 r / min for 30 min to obtain biochar.

[0036] Biochar and polylactic acid (PLA: Zhejiang Hisun, injection molding grade) were dissolved in dichloromethane, stirred for 3 hours, evaporated in a fume hood at 24°C for 6 hours, and then dried in an oven at 60°C for 10 hours; the dried PS-PLA composite material was placed in a grinder for 5 minutes, using intermittent grinding, grinding for 10 seconds and stopping for 5 seconds; the specimens were placed in an injection molding machine to obtain the specimens.

[0037] Example 1

[0038] (1) Pine sylvestris var. mongolica was thermally cracked at 550°C in a tube furnace to prepare pine charcoal (PS), the PS was dried at 60°C for 10 h, poured into a planetary ball mill, and ball milled at 350 r / min for 30 min;

[0039] (2) 12 g of ball-milled PS powder (7 μm) was added to the reaction solution (ethanol: deionized water = 225 g: 75 g), stirred evenly, and then sonicated for 15 min;

[0040] (3) The above solution was transferred to a 500 mL four-necked flask, stirred at a stirring speed of 200 r / min in a N2 atmosphere and heated to 75°C. After adding 3 g of AIBN, 30 g of MMA monomer was added dropwise at a dropping speed of 3 g / min. After the addition was complete, the reaction was carried out for 10 h. The product was poured into a washing solution for washing (ethanol: deionized water = 70 g: 30 g) and then centrifuged. The centrifuged product was dried at 60°C for 12 h to obtain a biochar-based toughened composite material (CP).

[0041] The CP and polylactic acid (PLA: Zhejiang Hisun, injection molding grade) obtained in Example 1 were dissolved in dichloromethane, stirred for 3 hours, evaporated in a fume hood at 24°C for 6 hours, and then placed in an oven at 60°C for drying for 10 hours; the dried CP-PLA composite material was placed in a pulverizer for 5 minutes, and intermittent pulverization was adopted, with pulverization for 10 seconds and rest for 5 seconds; and placed in an injection molding machine to obtain a specimen.

[0042] Depend on Figure 1 It can be seen that the interface defects between biochar and PLA can be effectively improved by modifying PLA with CP.

[0043] The tensile strength and flexural strength test results of the PLA strips prepared under different CP addition conditions in Example 1 are as follows: Figure 2 As shown in the figure, after adding CP, the mechanical properties of PLA are significantly improved. This improvement effect increases first and then decreases with the increase of CP addition, reaching the maximum when the addition amount is 10wt%.

[0044] Figure 3 It can be seen that the crystallinity of PLA can be effectively improved by modifying PLA with CP.

[0045] Example 2

[0046] The biochar-based toughened composite material is prepared by the same method as in Example 1, except that the pyrolysis temperature of the biochar is 550°C.

[0047] Example 3

[0048] The biochar-based toughened composite material is prepared by the same method as in Example 1, except that the pyrolysis temperature of the biochar is 750°C.

[0049] Figure 4 After adding CP synthesized by PS at different preparation temperatures, there are significant differences in the mechanical properties of PLA. The improvement effect on the mechanical properties of PLA shows a trend of first increasing and then decreasing with the increase of PS preparation temperature. When CP synthesized by PS at 550℃ is used, the improvement of the mechanical properties of PLA reaches the maximum.

[0050] Example 4

[0051] The biochar-based toughened composite material is prepared by the same method as in Example 1, except that rice husk char is prepared by pyrolysis of rice husk at 550° C. as biochar.

[0052] Example 5

[0053] The biochar-based toughened composite material is prepared by the same method as in Example 1, except that fallen leaves are pyrolyzed at 550° C. to obtain fallen leaf charcoal as the biochar.

[0054] Example 6

[0055] The biochar-based toughened composite material was prepared by the same method as in Example 1, except that the particle size of the PS powder was 0.5 μm.

[0056] Example 7

[0057] The biochar-based toughened composite material was prepared by the same method as in Example 1, except that the particle size of the PS powder was 70 μm.

[0058] In the present invention, incompatible biochar and PLA are prepared into engineering plastics having mechanical properties and thermal stability higher than those of raw materials in the presence of soft phase MMA units.

[0059] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A biochar-based toughened composite material for PLA, characterized in that: The composite material consists of biochar and methyl methacrylate polymer; the mass ratio of the biochar to the methyl methacrylate polymer is 2:

5.

2. The biochar-based toughened composite material for PLA according to claim 1, characterized in that: The biochar includes one or a combination of multiple of Pinus sylvestris charcoal, rice husk charcoal, fallen leaf charcoal and straw charcoal.

3. The biochar-based toughened composite material for PLA according to claim 2, characterized in that: The preparation temperature of the biochar is 350-750°C.

4. A method for preparing a biochar-based toughened composite material for PLA according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: (1) preparing biochar into biochar powder by ball milling; (2) dispersing biochar powder into a reaction solvent; (3) Adding a catalyst to a uniformly dispersed biochar solution in a nitrogen atmosphere, and continuously heating and stirring until the temperature reaches a preset temperature, then adding methyl methacrylate monomer in a dropwise manner for reaction, washing, centrifuging, and drying to obtain the biochar-based toughened composite material.

5. The preparation method according to claim 4, characterized in that: In step (1), the ball milling uses a planetary ball mill, the ball milling speed is 200-350 r / min, and the ball milling time is 0.1-2.5 h; The particle size of the biochar powder is 0.5-70 μm.

6. The preparation method according to claim 4, characterized in that: In step (2), the reaction solvent is a mixed solution of one or more of methanol, ethanol and deionized water.

7. The preparation method according to claim 4, characterized in that: In step (3), the catalyst is one of azobisisobutyronitrile and sodium dodecyl sulfate; the amount of catalyst added is 0.1%-1% of the mass of the methyl methacrylate monomer.

8. The preparation method according to claim 4, characterized in that: In step (3), the preset temperature is 60-100° C. and the reaction time is 2-10 h.

9. The preparation method according to claim 4, characterized in that: In step (3), the dropping speed of the methyl methacrylate monomer is 0.1-10 mL / min. The washing liquid used in the washing is a combination of one or more of methanol, ethanol and deionized water; The centrifugal speed is 3000-4200r / min; The drying temperature is 40-70° C., and the drying time is 4-12 hours.

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