Principles of Their Action

Ca and Zn stearates, 45% by weight Waxes, 23.5% by weight Fatty acid amides, 19% by weight Fatty acid esters, 12% by weight 

There are many different ways of thinking about the properties, functions, and classification of lubricants [5,8-20]. For example, in the case of internal lubricants for PVC, it is usually believed that, contrary to plasticizers, lubricants solvate only the surface of PVC spherical particles or nodules produced by agglomeration of PVC chains in the course of the polymerization reaction and that behave as independent units during the melt flow of the bulk polymer [21]. Thus the lubricant acts exactly as an oil in the case of bearing lubrication and the spherical agglomerates slide directly on a lubricant layer [22]. 

With a melt polymer a melt lubricant may form either a homogeneous phase or a mixture of the two separate liquids according to their mutual miscibility. This is the reason that melt PVC and a lubricant may form a two-phase system at least, made of spherical PVC agglomerates dispersed in a liquid solution of PVC single molecules and the melt lubricant or in the melt lubricant alone if it is not miscible with PVC [16]. 

The effect of lubrication on the processibility is shown in Fig. 2.2 for three types of differently polymerized PVC the emulsion polymerized polymer (curve 1) contains emulsifiers that act as lubricants [23]. Obviously, only this type of PVC with a low molecular weight can be processed without lubricant. The type of PVC used has also a great effect on the efficiency of each lubricant, as shown in Figs. 2.3 and 2.4 [23]. 

Mutual interaction between lubricants and other additives in the plastic material (such as stabilizers, fillers, etc.) that may affect their affinity to the polymer and produce undesired effects, such as plate-out (deposition of residues from the melt on the metal surfaces of the processing equipment). 

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The principle of their action is illustrated by the apparatus shown in Fig. 8.2. is a small cistern containing a mixture of sodium hydroxide (instead of lime for experimental convenience) and sodium carbonate. This flows through a funnel into a corked reaction chamber B, entering at the... 

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