PVC (polyvinyl chloride) is found in cling film, plastic shoes, leather products, films, cables, and plastic bags. As one of the top five general-purpose plastics, PVC has high strength, non-flammability, climate change resistance, and excellent geometric stability. pvc pipes, moreover, occupy the leading position in the market share of plastic pipes by virtue of their light weight, corrosion resistance, high pressure strength, and safety and convenience. Driven by the new infrastructure, PVC products continue to see peak development in the fields of water supply and drainage, agriculture, power and communication.
How to complete the high-quality progression of PVC products? In addition to raw materials, processing equipment, and processing technology, wax, a lubricant with good genes, is an important element!
PVC materials with heat-sensitive characteristics are processed and plasticized with 80% of the heat required from the frictional shear heat between the raw material and the screw, and it is these hot spots that cause PVC to be prone to the risk of degradation. How to control the friction between the screw/sleeve and the PVC to delay plasticization and achieve good external lubrication? How to increase the friction between PVC particles to promote plasticization and thus improve internal lubrication? Which wax can be added to achieve excellent balance of internal and external lubrication?
Saturated hydrocarbons can be divided into non-polar hydrocarbons (such as polyethylene wax and polypropylene wax) and polar hydrocarbons (such as chlorinated paraffin, oxidized polyethylene, etc.) according to their polarity. Saturated hydrocarbons can be divided according to molecular weight size; liquid paraffin wax (C16-C21), solid paraffin wax (C26-C32) microcrystalline paraffin wax (C32-C70) and low molecular weight polyethylene (molecular weight 1000-10000), etc., mainly used for PVC non-toxic external lubricants:.
(1) Liquid paraffin wax: commonly known as white oil, colorless and transparent liquid, can be used as transparent external lubricant of PVC, the dosage is about 0.5, the dosage will seriously affect the coloring.
(2) solid paraffin wax, also known as natural paraffin wax, white solid, can be used as pvc external lubricant, the amount of 0.1-1.0, the amount of too much will affect the transparency.
(3) Microcrystalline paraffin wax, also known as high melting point paraffin wax, white or light yellow solid in appearance, known as microcrystalline paraffin wax because of microcrystalline. It has better lubrication effect and thermal stability than other paraffin waxes. The dosage in PVC is small, generally 0.1-0.3 parts.
(4) low molecular weight polyethylene, also known as polyethylene wax, the appearance of white or light yellow solid powder, poor transparency, can be used for PVC extrusion and calendering process outside the lubricant, the amount is generally 0.5 copies.
(5) oxidized polyethylene wax, the partial oxidation product of polyethylene wax, the appearance of white powder. Excellent internal and external lubrication, good transparency, the amount of 0.2 – 1.0 copies.
(6) chlorinated paraffin wax, good compatibility with PVC, poor transparency, good effect with other lubricants, dosage of 0.5 parts or less is appropriate.
The n-alkane structure of Fischer-Tropsch wax is up to 97%, and the melting point is up to 110℃, with excellent thermal stability and light resistance. Tianshi Fischer-Tropsch wax has superb external lubricating effect. The narrow molecular weight distribution and thus lower precipitation risk and higher surface finish of the product greatly meet even the need for high speed and high throughput extrusion external lubrication such as pipes and sheets. Longer machine clean-up cycles during use result in better processing efficiency.
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