Polymer, chemical physics stearates

Most of physical and chemical properties of regular butyl and halobutyl are similar. Nevertheless, dehydrohalogenation, more sensitive for brominated polymer, is observed at high temperature and can occur during processing. The reaction is autocatalyzed by the evolved acid and stabilization consists of trapping this acid by calcium stearate and epoxidized soybean oil, which are added in the last phase of production process. 

Zinc and Calcium Stearate Synergism. With the Brabender plasti-corder, it is possible to follow the viscosity variations of a polymer because of physical or chemical modifications. The shape of the typical plasto-grams for PVC plasticized and stabilized with calcium stearate (Ca-(OCOR)2) (6.6 phr), zinc stearate (Zn(OCOR)2) (6.6 phr), and their mixture (3.3 phr both stearates), are shown in Figures 1, 2, and 3, respectively (-----). Because of degradation, the first peak corresponds to... 

Analogous cycles are observed in the polyacetal-steel and polyolefin-steel friction pairs. Physical-chemical processes can exert a favorable effect on the metal-polymer friction pair as well. For instance, metal-containing compounds of copper stearate and oleate types are formed in the contact zone as a result of tribochemical reactions when CFD copolymer rubs against copper. These compounds retard thermally destruction processes in CFD, serving as wear inhibitors (WI) for this system. 

Polymers contain various elements, metallic and nonmetallic. Some elements are a constituent part of the monomers, such as nitrogen in acrylonitrile or chlorine in poly(vinyl chloride), while other elements occur as impurities or are part of some additives (e.g., zinc stearate). Their concentrations range from a (tg per kg level to several percent. Analysis of the element content is especially important for manufacturing process control. Elements can be determined after chemical or physical destruction of polymer, or directly by nondestructive methods. 

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