Lubricants influence the behaviour of PVC compounds under the heat and shear experienced in processing machinery. They are essentially divided into 2 categories, viz. (i) Internal lubricants which reduce the inert-particle and inter-molecular friction, and (ii) External lubricants that reduce the friction effects at, and adhesion to the walls of processing machinery. An internal lubricant is highly compatible and the external lubricant on the other hand has a very poor compatibility with PVC resin. The transition between internal and external lubricating effect is fluid as most of the internal lubricants have certain external lubrication effect and vice versa. Lubricants having both the effects are called as “combined lubricants”.
Internal lubricants reduce the frictional forces occurring between the PVC particles and PVC molecule chains, thus reducing the melt viscosity. They are polar and thus are highly compatible with PVC. They help achieve excellent transparency even at high dosages and do not tend to exudate which helps in optimizing welding gluing and printing properties of the final product. External lubricants on the other hand are non-polar in nature such as paraffin and polyethylene waxes. The external lubrication effect is largely determined by the length of the hydrocarbon chain, its branching and its functional group. Due to poor compatibility with PVC, they come onto the surface of the compounded mass thereby reducing friction and adhesion between the hot PVC composition and the working surfaces of processing machinery and moulds. This makes movement of the composition through the machinery easier, and prevents deposition of the PVC composition on the hot metal surfaces; which in turns help in smooth processing of the PVC composition and reduces the chances of degradation.
External lubricants reduce the adhesion between PVC and metal surfaces. They are mostly non-polar such as paraffin and polyethylene waxes. The external lubrication effect is largely determined by the length of the hydrocarbon chain, its branching and its functional group. At high dosages they can lead to cloudiness and exudation.
Baerlocher lubricants range is sold under trade name Baerolub.
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