A molybdenum disulfide micro-nano composite modified polylactic acid composite material and a preparation method thereof

Abstract

A molybdenum disulfide micro-nano composite modified polylactic acid composite material and its preparation method, which relate to the fields of molybdenum disulfide lubricating materials and polylactic acid modification. Micron molybdenum disulfide particles are heat-treated at high temperature under a protective atmosphere, and after cooling, they are soaked in an activation solution to obtain surface-activated micron molybdenum disulfide particles; molybdate and sulfide are reacted in an acidic solution, and the generated precipitate is deposited on the surface of the activated micron molybdenum disulfide particles. After filtration, washing, drying, and calcination under a protective atmosphere, a molybdenum disulfide micro-nano composite is formed; then the above micro-nano composite is added to polylactic acid, and after melt blending and molding, a molybdenum disulfide micro-nano composite modified polylactic acid composite material is obtained. This composite material has excellent anti-friction performance, has good application prospects in the field of self-lubricating materials, and also has potential application value in fields such as medical antibacterial packaging materials.

Description

Technical Field

[0001] The present invention relates to the field of molybdenum disulfide lubricating materials and polylactic acid modification, and specifically relates to a molybdenum disulfide micro-nano composite modified polylactic acid composite material and a preparation method thereof. Background Art

[0002] Polylactic acid is a polyester polymerized from lactic acid. Its raw materials mainly come from lactic acid produced by the fermentation of starch-containing crops. It is a polymer material synthesized from natural resources, with non-toxic, biodegradable, good compatibility and absorbability. Replacing chemically synthesized plastic materials with polylactic acid has important significance in environmental protection and resource and energy conservation. Polylactic acid is generally a linear molecule with a relatively small and wide molecular weight distribution, relatively low strength and poor toughness. Usually, plasticization modification is required. However, with the decrease in hardness, the anti-friction performance of the plasticized modified polylactic acid still needs to be further improved.

[0003] Molybdenum disulfide has a layered structure, and it is easy to slip between layers. Therefore, it has excellent lubrication performance and is a commonly used solid lubricant, which can be used for the lubrication modification of polymers. Research shows that the performance of molybdenum disulfide is closely related to the size of its constituent particles. Molybdenum disulfide of different scales can exhibit different performances under different working conditions. In particular, molybdenum disulfide of different sizes may also show a synergistic lubrication effect. For example, larger molybdenum disulfide particles can isolate the friction pair and weaken the frictional shear by means of the slip between its own layers; while small molybdenum disulfide particles can enter the wear area to fill the grooves. In particular, nano-scale molybdenum disulfide can be lubricated by peeling and transferring to the surface of the friction pair. Molybdenum disulfide particles of different scales can act on the friction surface simultaneously because they have different lubrication mechanisms, thus showing a lubrication synergistic effect.

[0004] In view of this, the present invention attempts to modify molybdenum disulfide and compound it with polylactic acid to achieve the purpose of improving the friction performance of polylactic acid. Summary of the Invention

[0005] In order to solve the friction performance defects existing in the existing polylactic acid materials, the present invention provides a molybdenum disulfide micro-nano composite modified polylactic acid composite material and a preparation method thereof. By chemically depositing nano-scale molybdenum disulfide on the surface of larger micron-scale molybdenum disulfide particles, and then using the product for the filling modification of polylactic acid, this method can ensure that molybdenum disulfide particles of different sizes can be uniformly mixed, and better play their synergistic effect in polylactic acid.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A molybdenum disulfide micro-nano composite modified polylactic acid composite material, which is composed of polylactic acid and a molybdenum disulfide micro-nano composite. The molybdenum disulfide micro-nano composite is composed of molybdenum disulfide particles at the micron scale with nano-scale molybdenum disulfide particles deposited on their surfaces.

[0007] The present invention also provides a method for preparing a molybdenum disulfide micro-nano composite modified polylactic acid composite material, and the steps are as follows:

[0008] 1) Heat the molybdenum disulfide particles at the micron scale under a protective atmosphere at high temperature, and after cooling, soak them in an activation solution to obtain surface-activated molybdenum disulfide particles at the micron scale.

[0009] 2) React molybdate and sulfide in an acidic solution, and deposit the generated precipitate on the surface of the activated molybdenum disulfide particles at the micron scale. After filtration, washing, drying, and calcination under a protective atmosphere, a molybdenum disulfide micro-nano composite is formed.

[0010] 3) Add the molybdenum disulfide micro-nano composite to polylactic acid, and after melt blending and molding, a molybdenum disulfide micro-nano composite modified polylactic acid composite material is obtained.

[0011] As a preferred technical solution of the present invention, in the preparation method:

[0012] In step 1), the molybdenum disulfide particles at the micron scale are heat-treated under a rare gas or nitrogen atmosphere, the treatment temperature is 300 - 1000 °C, and the treatment time is 0.5 - 24 h. After heat treatment and cooling, soak them in hydrogen peroxide or an alkali solution for 0.5 - 24 h to obtain surface-activated molybdenum disulfide particles at the micron scale. The alkali solution is one or a combination of ammonia water, hydroxides of alkali metals or alkaline earth metals, and carbonates of alkali metals.

[0013] In step 2), dissolve molybdate and sulfide in water simultaneously, then add the activated molybdenum disulfide particles at the micron scale. Under stirring and at a temperature of 0 - 95 °C, add acid until the pH value is less than 3, and the precipitate generated by the reaction of molybdate and sulfide deposits on the surface of the activated molybdenum disulfide particles at the micron scale. The molybdate is sodium molybdate or ammonium molybdate, the sulfide is sodium sulfide or thioacetamide, the molar ratio of molybdate to sulfide is 1:1 - 10, the mass ratio of molybdate to the activated molybdenum disulfide at the micron scale is 1:0.1 - 10, and the mass ratio of molybdate to water is 1:10 - 2000. After the reaction is completed, filter, wash, dry, and then calcine under a rare gas or nitrogen atmosphere at 400 - 1000 °C for 0.2 - 12 h to form a molybdenum disulfide micro-nano composite.

[0014] In step 3), molybdenum disulfide micro-nano composite is added to polylactic acid and melt-blended and molded to prepare a modified polylactic acid composite material. The mass ratio of molybdenum disulfide micro-nano composite to polylactic acid is 1:4 to 1000.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] In the present invention, the surface of micron molybdenum disulfide is activated by heat treatment and immersion in an activation solution. Then, using sulfide and molybdate as reactants, molybdenum disulfide nanoparticles are deposited on the surface of the activated micron molybdenum disulfide particles, enabling uniform mixing of the two and fully exerting their synergistic lubrication effect. The prepared molybdenum disulfide micro-nano composite modified polylactic acid composite material has excellent anti-friction performance, good application prospects in the field of self-lubricating materials, and also has potential application value in fields such as medical antibacterial packaging materials. Description of the Drawings

[0017] Figure 1 are the X-ray diffraction patterns (a) of the raw material micron molybdenum disulfide particles and the molybdenum disulfide micro-nano composite prepared in the present invention, the scanning electron microscope photograph (b) of the raw material micron molybdenum disulfide particles, and the scanning electron microscope photograph (c) of the molybdenum disulfide micro-nano composite prepared in the present invention.

[0018] Figure 2 is the wear resistance (width of the wear scar after friction) of the molybdenum disulfide micro-nano composite filled and modified polylactic acid composite material prepared in the present invention compared with that of pure polylactic acid. Detailed Embodiments

[0019] Example 1

[0020] Micron molybdenum disulfide is heat-treated at 400 °C for 2 h under nitrogen conditions, and then activated by soaking in hydrogen peroxide for 12 h. 0.67 g of sodium molybdate dihydrate and 1.27 g of thioacetamide are simultaneously dissolved in 50 g of water, and then 0.8 g of the above-activated molybdenum disulfide micron particles are added. Under stirring and at 90 °C, hydrochloric acid is added until the pH value is less than 0.5. The precipitate generated by the reaction of sodium molybdate and thioacetamide is deposited on the surface of the activated micron molybdenum disulfide particles. After the precipitate is filtered, washed, and dried, it is calcined in a nitrogen atmosphere at 480 °C for 1 h, and then cooled to obtain molybdenum disulfide micro-nano composite. Take 0.4 g of the above molybdenum disulfide micro-nano composite and add it to 40 g of polylactic acid, and obtain the molybdenum disulfide micro-nano composite modified polylactic acid composite material by melt-blending and molding.

[0021] Figure 1The X-ray diffraction patterns (a) of the raw material micron molybdenum disulfide particles and the molybdenum disulfide micro-nano composite prepared in the present invention, the scanning electron microscope photograph (b) of the raw material micron molybdenum disulfide particles, and the scanning electron microscope photograph (c) of the molybdenum disulfide micro-nano composite prepared in the present invention. According to the molybdenum disulfide standard PDF card 37-1492, Figure 1 (a) All the main diffraction peaks can be indexed to molybdenum disulfide, indicating that the prepared micro-nano composite is molybdenum disulfide and there are no obvious impurities; combined with Figure 1 (b) and 1(c), it can be seen that molybdenum disulfide nanoparticles are deposited on the surface of the molybdenum disulfide micron particles in the present invention, proving that the obtained is a micro-nano composite.

[0022] Figure 2 It is the comparison of the wear scar width after friction of the micro-nano composite modified polylactic acid (mass ratio 1:100) and the unmodified polylactic acid. As can be seen from the figure, the wear scar width of the polylactic acid filled with the micro-nano composite can be reduced by about 55%.

[0023] Example 2

[0024] The micron molybdenum disulfide is heat-treated at 600 °C for 3 h under nitrogen conditions, and then activated by soaking in sodium hydroxide solution for 5 h. 1 g of sodium molybdate dihydrate and 5.4 g of sodium sulfide nonahydrate are simultaneously dissolved in 100 g of water, and then 5 g of the above-activated molybdenum disulfide micron particles are added. Under stirring and at 85 °C, hydrochloric acid is added until the pH value is less than 2. The precipitate generated by the reaction of sodium molybdate and sodium sulfide is deposited on the surface of the activated molybdenum disulfide micron particles. After the precipitate is filtered, washed, and dried, it is calcined in a nitrogen atmosphere at 680 °C for 2 h, and the molybdenum disulfide micro-nano composite is obtained after cooling. The X-ray diffraction pattern and scanning electron microscope photograph of the prepared molybdenum disulfide micro-nano composite are basically similar to those of Example 1.

[0025] Take 1 g of the above molybdenum disulfide micro-nano composite and add it to 50 g of polylactic acid, and a molybdenum disulfide micro-nano composite modified polylactic acid composite material is obtained by melt blending and molding. The wear resistance of this composite material is basically similar to that of Example 1.

[0026] Example 3

[0027] Micron-sized molybdenum disulfide is heat-treated at 500 °C for 4 h under argon atmosphere, and then activated by soaking in ammonia water for 10 h. 2 g of sodium molybdate dihydrate and 5 g of thioacetamide are simultaneously dissolved in 200 g of water, and then 10 g of the above-activated micron-sized molybdenum disulfide particles are added. Under stirring at 80 °C, hydrochloric acid is added until the pH value is less than 1. The precipitate generated from the reaction of sodium molybdate and thioacetamide deposits on the surface of the activated micron-sized molybdenum disulfide particles. After filtration, washing, and drying, the precipitate is calcined in an argon atmosphere at 580 °C for 0.5 h, and after cooling, a molybdenum disulfide micro-nano composite is obtained. The X-ray diffraction pattern and scanning electron microscope photograph of the prepared molybdenum disulfide micro-nano composite are basically similar to those of Example 1.

[0028] Take 1.5 g of the above molybdenum disulfide micro-nano composite and add it to 50 g of polylactic acid, and a molybdenum disulfide micro-nano composite modified polylactic acid composite material is obtained by melt blending and molding. The wear resistance of this composite material is basically similar to that of Example 1.

[0029] Example 4

[0030] Micron-sized molybdenum disulfide is heat-treated at 350 °C for 4 h under nitrogen atmosphere, and then activated by soaking in sodium carbonate solution for 10 h. 1 g of ammonium molybdate and 1.5 g of thioacetamide are simultaneously dissolved in 100 g of water, and then 2 g of the above-activated micron-sized molybdenum disulfide particles are added. Under stirring at 82 °C, hydrochloric acid is added until the pH value is less than 1. The precipitate generated from the reaction of ammonium molybdate and thioacetamide deposits on the surface of the activated micron-sized molybdenum disulfide particles. After filtration, washing, and drying, the precipitate is calcined in an argon atmosphere at 480 °C for 0.5 h, and after cooling, a molybdenum disulfide micro-nano composite is obtained. The X-ray diffraction pattern and scanning electron microscope photograph of the prepared molybdenum disulfide micro-nano composite are basically similar to those of Example 1.

[0031] Take 2 g of the above molybdenum disulfide micro-nano composite and add it to 50 g of polylactic acid, and a molybdenum disulfide micro-nano composite modified polylactic acid composite material is obtained by melt blending and molding. The wear resistance of this composite material is basically similar to that of Example 1.

[0032] The above content is only an example and explanation of the concept of the present invention. Those skilled in the art of this technology can make various modifications, supplements, or use similar methods to replace the specific embodiments described, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should fall within the protection scope of the present invention.

Claims

1. Preparation method of molybdenum disulfide micro-nano composite modified polylactic acid composite material, characterized in that, the steps are as follows: 1) Heat-treat micron molybdenum disulfide particles under rare gas or nitrogen atmosphere, the treatment temperature is 300~1000 °C, and the treatment time is 0.5~24 h; after heat-treatment, cool and then soak in hydrogen peroxide or alkali solution for 0.5~24 h to obtain surface-activated micron molybdenum disulfide particles, and the alkali solution is one or a combination of more of ammonia water, hydroxides of alkali metals or alkaline earth metals, and carbonates of alkali metals; 2) Dissolve molybdate and sulfide in water at the same time, then add the activated molybdenum disulfide micron particles, and add acid to a pH value less than 3 under stirring and at a temperature of 0~95 °C. The precipitate generated by the reaction of molybdate and sulfide deposits on the surface of the activated micron molybdenum disulfide particles; after the reaction, filter, wash, dry, and then calcine at 400~1000 °C for 0.2~12 h under rare gas or nitrogen atmosphere to generate molybdenum disulfide micro-nano composite; the molybdate is sodium molybdate or ammonium molybdate, the sulfide is sodium sulfide or thioacetamide, the molar ratio of molybdate to sulfide is 1∶1~10, and the mass ratio of molybdate to activated micron molybdenum disulfide is 1∶0.1~10; 3) Add the molybdenum disulfide micro-nano composite to polylactic acid according to the mass ratio of molybdenum disulfide micro-nano composite to polylactic acid of 1∶4~1000, and obtain the molybdenum disulfide micro-nano composite modified polylactic acid composite material after melt blending and molding. It is composed of polylactic acid and molybdenum disulfide micro-nano composite, and the molybdenum disulfide micro-nano composite is composed of nano-scale molybdenum disulfide particles deposited on the surface of micron-scale molybdenum disulfide particles.

2. Molybdenum disulfide micro-nano composite modified polylactic acid composite material prepared by the method according to claim 1, characterized in that, it is composed of polylactic acid and molybdenum disulfide micro-nano composite, and the molybdenum disulfide micro-nano composite is composed of nano-scale molybdenum disulfide particles deposited on the surface of micron-scale molybdenum disulfide particles.

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