At present, plastic products are used in all aspects of our lives, such as building materials, transportation, automobile manufacturing and so on. However, in the process of using plastic products, the toughness and strength of the products are often not well combined. It can be said that the toughening and strengthening of plastics is an important problem to be solved in the application of polymer materials.
From the perspective of materials science, high specific strength, high specific modulus, high toughness, and wear resistance in plastic applications are all related to plastic toughness and strength. Plastic strength and toughness are two particularly important but contradictory mechanical properties in structural materials.
Advantages of Calcium Carbonate Toughened Plastics
Calcium carbonate is a commonly used inorganic filler in the plastic industry. It has rich raw materials, mature technology and affordable price, and is widely used in five major plastic products. In terms of ultra-fine or nano-calcium carbonate materials, they have a very high surface area, which can significantly improve the impact resistance (toughness) of materials in polymers, and can also improve tensile strength and elongation at break. When composited with polymers, the surface effect, small size effect, quantum effect and synergistic effect of nanoparticles will greatly improve the comprehensive performance of composite materials.
Method for filling modified plastics with calcium carbonate
1. Sol-gel method
This method is carried out in a precursor system such as a highly chemically active siloxane metal compound. The precursor undergoes hydrolysis and condensation reactions to form a stable and uniform transparent gel system, and at the same time forms CaCO3 particles, and the particles are highly dispersed in the gel. in the system. With the passage of time, the gel system gradually loses its fluidity, and then the gel is dried or sintered to obtain a nanostructured composite material. The method makes CaCO3 highly dispersed in the organic matrix, fully exerts the performance advantages of the nanometer material, and the prepared composite material has excellent properties. However, due to the shrinkage stress generated in the drying process, this method is difficult to obtain large quantities of products and cannot be industrialized.
2. In situ polymerization method
This method is to uniformly mix CaCO3 into the plastic monomer in a certain proportion. When the plastic monomer is polymerized to prepare polymer plastics, CaCO3 particles can be effectively attached to the plastic monomer due to the physical or chemical reaction between the CaCO3 particles and the plastic monomer. Surface, and with the polycondensation process of the monomer, it is evenly dispersed in the plastic matrix. The composite material is prepared by the method, the reaction condition is mild, and the molding effect can be excellent without changing the characteristics of the inorganic nanoparticles. However, the current technology is still immature and cannot be used on a large scale.
3. Blending method
This method uses physical blending to mix CaCO3 particles into the polycondensed plastic matrix in the form of emulsion blending, melt blending and mechanical blending. The blending method has the advantages of simple and controllable process, simple equipment, the preparation of calcium carbonate and plastic matrix can be carried out step by step, without mutual interference, and can be produced in batches. It is also one of the most common methods for plastic modification at present. However, how to uniformly disperse calcium carbonate in the plastic matrix during the blending process is also a long-term issue.
Prospects of Inorganic Powder Toughened Plastics Technology
From a macro perspective, in the future, plastic toughening and strengthening will mainly develop towards the material composite technology route. For example, by selecting low-cost inorganic materials, through nanopowders, one-dimensional structure materials (wollastonite, calcium carbonate whiskers, short glass fibers), two-dimensional structure materials (talcum powder, mica powder, graphene) three-dimensional structure ( Barium sulfate, glass microspheres, etc. improve the comprehensive performance of materials and prepare masterbatches, which can replace nano-toughened masterbatches and glass fiber reinforced masterbatches, and have wide adaptability.
For calcium carbonate, the price is an advantage, which can effectively ensure the amount of use; the shape and machinability is another advantage, such as calcium carbonate whiskers, spherical, porous, cake-shaped, etc.; there are rich categories, including light calcium and heavy calcium If there are various powder properties, it can be compounded with a variety of minerals. In the face of ordinary powder materials and plastic products, the wide applicability of calcium carbonate is also a big advantage.