Due to the poor thermal stability of PVC, corresponding stabilizers must be added to repair the defects of the PVC chain, and at the same time absorb the HCL produced by PVC dechlorination in time. At the same time, due to the processing characteristics of high viscosity and large shear of PVC, it is necessary to add corresponding lubricants such as polyethylene wax lubricants when adding stabilizers.
Polyethylene wax, namely PE wax, low molecular weight polyethylene, is directly polymerized from ethylene. The products synthesized by different synthesis processes and catalytic systems are different in molecular weight, molecular weight distribution and molecular chain structure, and the performance of the corresponding products is different. There will also be significant differences. PE wax is usually white powder, the average molecular weight is generally 1500-5000, and the melting point is 100-120 degrees. It has excellent external lubrication effect in PVC processing, and can effectively improve the fluidity, output, dispersion, surface brightness and mold release of PVC processing. Due to its large molecular weight and high melting point, its high temperature stability is very good, and it shows a strong external lubrication effect under high temperature and high shear conditions.
Polyethylene wax products can effectively improve the thermal stability of PVC and the fluidity of the processing process, increase the extrusion efficiency of PVC products, improve the surface gloss of products, and effectively reduce the precipitation of PVC products during processing.
At present, the PE waxes on the domestic market are mostly divided into several types:
1. Ethylene is homopolymerized into PE wax. The PE wax produced by this method has good external lubricity, high gloss, narrow molecular weight distribution and very stable quality. The representative products are the A-C series of Honeywell.
2. The by-product of the ethylene polymerization process, commonly known as the second brand wax, is the PE wax obtained through the purification process. Due to certain fluctuations, due to the characteristics of the refining process, there will inevitably be more low-melting components in the product.
3. PVC thermally stable medium and low molecular weight polyethylene cracking product, commonly known as cracking wax, the cracking process is simple and easy to operate, but the molecular weight distribution of the product fluctuates to a certain extent with the production process, the quality is relatively good, and there will still be a small part of low molecular weight. melting point components.
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