External Lubricant
Introduction
External lubricant and molding resin compatibility is poor, so commonly used in molding machinery or mold, it and resin between the formation of a lubrication layer, easy resin flow and products demodulation, such as paraffin wax.
Product Description
The function of PVC lubricant is to improve the fluidity of resin and the demoulding of products in plastic processing to prevent defects due to adhesion in the machine or mold.Lubricant is the demoulding property of neutralized products in plastic processing to prevent defects due to adhesion in the machine or mold.Generally added to the mold plastic or coated on the cavity surface.Commonly used lubricants are fatty acids and their salts, long-chain aliphatic hydrocarbons.According to the different mechanism of lubricant action can be divided into external lubricant and internal lubricant.
Properties of PVC lubricants
(1) Calcium stearate:White powder, melting point 148-155℃, non-toxic, excellent lubricity and processing, no sulfurization pollution, used with base lead salt and lead soap, can improve the gelation speed, the dosage is generally 0.1-0.4PHR.
(2) Oxidized polyethylene waxWhite or flaxen powder or particle, although oxidized polyethylene wax contains a small number of polar groups, it is still incompatible with PVC, but lubrication efficiency is higher, can improve the lubricity between polymer and metal, improve extrusion efficiency, improve the dispersancy of colorant, give products good transparency and luster.The dosage of 0.1 0.5 PHR.
(3) Stearic acidWhite or yellowish particles, melting point 70-71℃.It is volatilized slowly at 90-100℃ and used as external lubricant in hard PVC processing. The dosage is generally 0.2-0.5PHR and has the effect of preventing chromatography scaling. However, the dosage is too large and easy to spray frost.
(4) Glycerol stearatePowder, melting point 85-87℃, excellent heat resistance and fluidity, can increase the amount of filler, and can promote plasticization.When used with waxes, the thermal stability of PVC-U can be improved.General dosage is 0.2-0.6PHR.In practice, it has been found that when two or more lubricants are used together, they have different effects than when they are used alone.In the different profile formula, most of the use of compound way
(5) Paraffin waxMelting point 57-63℃, without polar groups, is a typical external lubricant.Due to its low melting point, easy to evaporate, melt viscosity is small, only in a narrow range of lubrication, suitable for single and double screw extruder extrusion, general dosage is 0.1-0.8PHR.The transparency of this product is poor, easy to white.
(6) Polyethylene waxWhite powder has a softening point of about 100-117℃. Due to its relatively large molecular weight, high melting point and low volatility, it also shows obvious lubrication effect at higher temperature and shear rate.Suitable for extruding hard PVC with single and double screw, the usual dosage is 0.1-0.5PHR.
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