Biodegradable materials are currently being touted. Due to factors such as material degradability and cost, currently biodegradable materials on the market generally choose starch, cellulose, etc. as fillers. The composite of starch and polymer materials can be made into degradable materials. Generally, starch or its derivatives are added as additives to synthetic polymers to improve the biodegradability of synthetic polymers. When the material is degraded, the porous polymer remaining due to the degradation of starch is prone to further degradation reactions such as oxidation. However, starch, cellulose and resin have poor compatibility, insufficient temperature resistance, and high cost, so they are not suitable for large-scale filling. Talcum powder, calcium carbonate, etc. are non-metallic mineral powdefrs. They have the advantages of low price, sufficient raw materials, high fineness, good whiteness, and easy color matching. At the same time, it can also improve the dimensional stability, temperature resistance and rigidity of plastic products, and improve the processing performance of plastics.
1. Talcum powder
The addition of talc to biodegradable plastics can increase the rigidity, thermal deformation temperature, dimensional stability, surface hardness, etc. of the material. At the same time, ultrafine talc can also be used as an inorganic nucleating agent for polylactic acid (PLA). Adding an appropriate amount of ultrafine talc powder can increase the crystallinity and crystallization rate of polylactic acid, and greatly improve its mechanical properties. Talc has three major roles in the modification of polylactic acid.
a. Cost reduction: The preparation method of talc-filled polylactic acid composite material provides a heat-resistant polylactic acid composite material preparation technology and method with beautiful appearance, good rigidity, short product molding cycle, light weight and low price.
b. Improve strength: The composite material prepared by melting and blending natural talcum powder is a completely biodegradable material. It has excellent mechanical properties, among which the tensile strength can reach 70MPa.
c. Improve heat resistance: Polylactic acid has better heat resistance due to its own crystallization and the promotion of crystallization of nucleating agent talc.
2. Calcium carbonate
Calcium carbonate is filled with biodegradable plastics, which can accelerate the degradation of biodegradable plastics. At the same time, calcium carbonate can be directly used as a carbon source by some inorganic nutrient microorganisms. The organic acid produced by microorganisms in the soil and the nitric acid and sulfuric acid produced by nitrifying bacteria and sulfur bacteria can further improve the solubility of calcium carbonate. The role of calcium carbonate in biodegradable plastics
a.Promote degradation: calcium carbonate particles can increase the distance between resin molecules, reduce the force of the polymer chain segment, hinder the re-crosslinking of macromolecular free radicals, promote free radical chain scission reaction caused by photodegradation, and accelerate the degradation of biodegradable plastics.
b. Easy to decompose: When buried in a humid environment, calcium carbonate can chemically dissolve, and it is directly used by some inorganic nutrient microorganisms as a carbon source.
c. Reduce viscosity and improve fluidity: The calcium carbonate after surface treatment increases the viscosity of the degraded plastic, improves the fluidity of the material, and reduces energy consumption.