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Application Advantages of Active Ultrafine Heavy Calcium in
DateTime:2019-06-26 15:14Click:
Heavy calcium carbonate is a kind of powdery inorganic filler, which has a series of advantages such as high chemical purity, inertia, difficult chemical reaction, good thermal stability, good dispersion and so on. It has been widely used in many fields, especially in the plastic industry.   However, with the development of plastic industry, especially the wide application of polymer materials, ordinary fine heavy calcium can not meet the requirements of functional reinforcement of high-grade plastic products, while activated superfine heavy calcium can solve this problem.   After surface modification, the increment and function of superfine heavy calcium with maximum particle size (D97) of less than 10 microns were improved, and then applied to PVC products, the production cost of PVC products could be effectively reduced, and the heat resistance, dimensional stability, impact strength and processing performance could be improved.   Because of its large particle size, activated heavy calcium with ordinary fineness can roughen the surface of products when it is used in PVC, PE, PS and other plastic products, thus reducing the performance and quality of products. Therefore, in order to avoid or slow down the decline of product quality, fine or ultra-fine calcium carbonate must be used in medium and high-grade pigments on the market.   In order to make superfine heavy calcium more widely used in plastics, rubber, coatings and other industries, scientific researchers conducted a detailed comparative study. It has been proved by a lot of experiments that compared with the properties of PVC plastics filled with activated light calcium, activated superfine heavy calcium can play an incremental filling and functional reinforcing role in PVC products, and the effect of adding active heavy calcium processed with different modified materials in PVC products is also different.   Firstly, the impact strength of the composites increases gradually with the increase of the content of active superfine heavy calcium (titanate modified) filling system, reaching the maximum value when the content is 12%. Thereafter, the impact strength of the composites decreases with the increase of calcium carbonate content. For the active light calcium filling system, the impact strength of the composites decreases with the increase of its dosage. This shows that activated light calcium only plays the role of filling or reducing costs, while ultra-fine activated heavy calcium can effectively improve the impact strength of products.   Secondly, the filling effect of ultra-fine heavy calcium modified by coupling agent is better than that of hard ester acid modified ultra-fine heavy calcium, and also better than that of active light calcium. However, the effect of different coupling agents on filling effect is not obvious. This is because the surface treatment of superfine heavy calcium carbonate by hard ester acid can only improve the dispersion of calcium carbonate in polymers, while the coupling agent reacts with hydroxyl groups on the surface of calcium carbonate to form chemical bonds, coats the surface of calcium carbonate with a single molecular film of coupling agent, and chemically crosslinks with PVC polymer at the other end. Physical winding makes calcium carbonate and PVC combine well, and the product has good elasticity and impact resistance.   Thirdly, the filling effect of active superfine calcium modified by coupling agent in soft PVC products is obviously better than that of hard ester acid modified active light calcium. The tensile strength, right angle tear strength and elongation at break of products are all increased by more than 10%.   In conclusion, the effect of filling PVC soft and hard products with active superfine heavy calcium is better than that of active light calcium because of its toughening effect of rigid particles. When the superfine heavy calcium treated by coupling agent is applied to PVC profiles and other products, it can achieve incremental filling and reinforcing effect. When the filling amount reaches 15 phr, the physical and mechanical properties of the products still meet the requirements of the national standard, and some properties are higher than those of the products filled with 8 PHRs of active light calcium.
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