Preparation method of biochar-based PLA composite material for 3D printing

Abstract

The invention relates to the technical field of material preparation, in particular to a preparation method of a charcoal-based PLA composite material for 3D printing. Comprising the following steps: (1) dispersing biochar into an acid solution, heating at 30-80 DEG C, uniformly stirring, adding a strong oxidant, continuously keeping at 30-80 DEG C, reacting for 1-10 hours, centrifuging and drying to obtain a solid product 1; (2) adding the solid product 1 into thionyl chloride, heating and refluxing at 60-90 DEG C for 6-12 hours, evaporating the solvent to dryness, washing with dichloromethane, centrifuging and drying to obtain a solid product 2; (3) adding the solid product 2 into ethylene glycol, heating and refluxing at 140 DEG C for 24 hours, filtering, washing and drying to obtain a solid product 3; and (4) adding PMMA, the solid product 3 and PLA into a wire extruding machine to prepare the composite material. The strength and the toughness of the prepared composite material are enhanced, and the thermal stability and the crystallization property are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular, to a method for preparing a biochar-based PLA composite material for 3D printing. Background Art

[0002] Biochar is widely available and inexpensive. It is a carbon-based material formed by the pyrolysis of biomass (such as wood and agricultural waste) under anaerobic conditions, and has a porous structure and a high surface area. Biochar has great application potential in the field of modified polymer materials. Polylactic acid (PLA), as a bio-based, degradable plastic, has the advantages of being environmentally friendly and renewable. However, PLA's mechanical properties (such as toughness, tensile strength), thermal stability, and processing properties are insufficient, and the decrease in thermal stability after 3D printing limits its wide application. In order to overcome these shortcomings, in recent years, researchers have tried to modify it by adding different fillers. Among them, biochar, as a green and sustainable filler, has attracted widespread attention. However, the poor dispersibility of biochar in PLA, poor interfacial compatibility with PLA, and poor interfacial adhesion have seriously limited the application of biochar in green materials such as PLA. Summary of the invention

[0003] In order to solve the problems of incompatibility, poor interface and weak dispersion ability between biochar and PLA matrix. The present invention provides a method for preparing a biochar-based PLA composite material for 3D printing. The surface of biochar is modified by ethylene glycol to improve the mechanical, thermal stability and crystallinity of PLA. The biochar-based composite material prepared by the method can regulate the mechanical, thermal stability and crystallinity of PLA by adjusting the preparation temperature and surface polarity of biochar.

[0004] In order to achieve the above object, the technical solution of the present invention is as follows:

[0005] The present invention provides a method for preparing a biochar-based PLA composite material for 3D printing, the method comprising the following steps:

[0006] (1) Dispersing biochar into an acid solution, heating at 30-80° C. and stirring evenly, adding a strong oxidant, and continuing to keep the mixed solution at 30-80° C. for reaction for 1-10 hours, centrifuging, and drying to obtain a solid product 1;

[0007] (2) adding the solid product 1 to thionyl chloride, heating under reflux at 60-90° C. for 6-12 h, evaporating the solvent, washing with dichloromethane, centrifuging, and drying to obtain a solid product 2;

[0008] (3) adding the solid product 2 to ethylene glycol, heating under reflux at 140° C. for 24 h, filtering, washing, and drying to obtain a solid product 3;

[0009] (4) PMMA, solid product 3 and PLA are added into an extruder to prepare the biochar-based PLA composite material.

[0010] In the above step (1), the strong oxidant is added in batches for safety considerations.

[0011] Preferably, in step (1), the biochar comprises one or a combination of Pinus sylvestris charcoal, rice husk charcoal, fallen leaf charcoal, and straw charcoal;

[0012] The biochar is prepared by pyrolyzing biomass at 300-850°C.

[0013] Preferably, in step (1), the acid solution is a combination of one or more of an acetic acid aqueous solution, a hydrochloric acid aqueous solution, a sulfuric acid aqueous solution, and a nitric acid aqueous solution; and the pH of the acid solution is 1-5.

[0014] Preferably, in step (1), the strong oxidant is H 2 O 2 .

[0015] Preferably, in step (1), in step (1), the drying temperature is 40-80°C.

[0016] Preferably, in step (2), the mass ratio of the solid product 1 to thionyl chloride is 1:(10-12).

[0017] Preferably, in step (2), the drying temperature is 50-70°C.

[0018] Preferably, in step (3), the mass ratio of ethylene glycol to solid product 2 is (2-10):1.

[0019] Preferably, in step (4), the extruder adopts a two-stage heating method, the melting zone temperature is 180-190°C, and the extrusion temperature is 170-185°C.

[0020] Preferably, in step (4), the mass ratio of PMMA, PLA and solid product 3 is (1-10): (80-95): (1-10).

[0021] The present invention makes full use of the characteristics of biochar surface modification and carboxylation, loads ethylene glycol on the biochar surface, utilizes the lubricity of ethylene glycol to effectively improve the dispersion ability of biochar, and can effectively improve the mechanical properties and crystallization properties of PLA. By strengthening PLA by modifying biochar with ethylene glycol, the mechanical properties, thermal stability and processing properties of PLA can be significantly improved. The interfacial compatibility between biochar and PLA is improved, so that the strength and toughness of the composite material are enhanced, the thermal stability and crystallization properties are improved, and the environmental friendliness of the material is still maintained, which is a green, sustainable and high-performance material solution.

[0022] The beneficial effects of the present invention are:

[0023] (1) The biochar-based PLA composite material prepared by the present invention, the raw material of biochar is usually agricultural waste or wood waste, and its production cost is relatively low. Compared with some expensive synthetic materials, biochar can effectively reduce the production cost.

[0024] (2) The present invention strengthens PLA by modifying biochar with ethylene glycol, which can significantly improve the mechanical properties, thermal stability and processing properties of PLA. The interfacial compatibility between biochar and PLA is improved, so that the strength and toughness of the composite material are enhanced, and the thermal stability and crystallization properties are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The mechanical properties test results of the biochar-based PLA composite material prepared in Example 1 printed into a test standard specimen;

[0026] Figure 2 The thermal stability test results of the biochar-based PLA composite material prepared in Example 1 printed into a test standard specimen, a is TG, b is DTG;

[0027] Figure 3 The activation energy test results of the biochar-based PLA composite material prepared in Example 1 printed into a test standard specimen;

[0028] Figure 4 is the XRD pattern of the biochar-based PLA composite material prepared in Example 1;

[0029] Figure 5 The mechanical properties test results of the biochar-based PLA composite material prepared in Example 2 printed into a test standard specimen;

[0030] Figure 6 The mechanical properties test results of the biochar-based PLA composite material prepared in Example 3 printed into test standard specimens. DETAILED DESCRIPTION

[0031] 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.

[0032] Example 1

[0033] (1) The pine charcoal powder (PS) prepared by slow pyrolysis (temperature of 550°C) was dispersed in an acetic acid aqueous solution (V 乙酸：V去离子水 =10:15, pH: 3-4), stirred and heated to 48°C, and H 2 O 2 , and keep adding 10 mL of H into the reactor every 10 min. 2 O 2 , added 6 times in total, kept the temperature for 4 hours, centrifuged at 3500r / min for 10 minutes, dried at 70°C for 10 hours, and obtained a solid product 1;

[0034] (2) Take the solid product 1 and put it into a three-necked flask, add thionyl chloride (SOCl 2 ), solid product 1 and SOCl 2 The mass ratio of is 1:12, reflux at 82°C for 14h, distill the solution in the reaction container to dryness at 90°C, wash the product with dichloromethane and centrifuge to remove thionyl chloride adsorbed on the surface, and dry at 60°C for 12h to obtain a solid product 2;

[0035] (3) 10 g of solid product 2 was added to 100 g of ethylene glycol, refluxed at 140° C. for 24 h, filtered while hot, washed with a large amount of water and ethanol, and dried to obtain a solid product 3;

[0036] (4) PMMA, PLA (PLA: Hisun 110) and solid product 3 in a mass ratio of 2.5:95:2.5 were dried and added to an extruder to prepare a biochar-based PLA composite material for 3D printing, wherein the temperature of the melting zone of the extruder was 190°C and the temperature of the extrusion zone was 185°C.

[0037] The biochar-based PLA composite material prepared in Example 1 was printed into a test standard specimen.

[0038] Depend on Figure 1-3 It can be seen that after 3D printing, the mechanical properties and thermal stability of the material have been significantly improved. This is because the interaction between the modified PLA molecular chains is stronger, and the ethylene glycol-modified biochar increases the entanglement of the molecular chains between PLA and PMMA, and improves the deformation resistance of the composite material molecular chains. Figure 3It can be seen that the activation energy of the modified PLA material is higher than that of pure PLA when reaching the highest degradation temperature. This shows that in order to relax the molecular chain of modified PLA, it needs to absorb more heat than pure PLA. This also shows that modified biochar can significantly improve the intermolecular interaction between PLA molecular chains and modified biochar.

[0039] Depend on Figure 4 It can be seen that after adding solid product 3, the crystallization performance of PLA is significantly improved.

[0040] Example 2

[0041] The biochar-based PLA composite material was prepared by the same method as in Example 1, except that the acid solution was a hydrochloric acid aqueous solution (V 水 :V 酸 =10:3, pH=1).

[0042] Example 3

[0043] The biochar-based PLA composite material was prepared by the same method as in Example 1, except that the acid solution was a sulfuric acid aqueous solution (V 水 :V 酸 =10:3, pH=1).

[0044] 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 method for preparing a biochar-based PLA composite material for 3D printing, characterized in that: The method comprises the following steps: (1) Dispersing biochar into an acid solution, heating at 30-80° C. and stirring evenly, adding a strong oxidant, and continuing to keep the mixed solution at 30-80° C. for reaction for 1-10 hours, centrifuging, and drying to obtain a solid product 1; (2) adding the solid product 1 to thionyl chloride, heating under reflux at 60-90° C. for 6-12 h, evaporating the solvent, washing with dichloromethane, centrifuging, and drying to obtain a solid product 2; (3) adding the solid product 2 to ethylene glycol, heating under reflux at 140° C. for 24 h, filtering, washing, and drying to obtain a solid product 3; (4) PMMA, solid product 3 and PLA are added into an extruder to prepare the biochar-based PLA composite material.

2. The preparation method according to claim 1, characterized in that: In step (1), the biochar comprises a combination of one or more of Pinus sylvestris charcoal, rice husk charcoal, fallen leaf charcoal, and straw charcoal; The biochar is prepared by pyrolyzing biomass at 300-850°C.

3. The preparation method according to claim 1, characterized in that: In step (1), the acid solution is a combination of one or more of an acetic acid aqueous solution, a hydrochloric acid aqueous solution, a sulfuric acid aqueous solution, and a nitric acid aqueous solution; and the pH of the acid solution is 1-5.

4. The preparation method according to claim 1, characterized in that: In step (1), the strong oxidant is H2O2.

5. The preparation method according to claim 1, characterized in that: In step (1), in step (1), the drying temperature is 40-80°C.

6. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of the solid product 1 to thionyl chloride is 1:(10-12).

7. The preparation method according to claim 1, characterized in that: In step (2), the drying temperature is 50-70°C.

8. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of ethylene glycol to solid product 2 is (2-10):

1.

9. The preparation method according to claim 1, characterized in that: In step (4), the extruder adopts a two-stage heating method, the melting zone temperature is 180-190°C, and the extrusion temperature is 170-185°C.

10. The preparation method according to claim 1, characterized in that: In step (4), the mass ratio of PMMA, PLA and solid product 3 is (1-10): (80-95): (1-10).

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