Polyfvinyl chloride applications

Whilst such stabilisers have found use in many chlorine-containing polymers their main application has been with polyfvinyl chloride). These additives will be considered in Chapter 12. 

A plasticizer is a material that enhances the processibiIity or flexibility of the polymer with which it is mixed. The plasticizer may be a liquid or solid or another polymer. For example, rigid polyfvinyl chloride) is a hard solid material used to make credit cards, pipe, house siding, and other articles. Mixing with about 50-100 parts by weight of phthalate ester plasticizers converts the polymer into leathery products useful for the manufacture of upholstery, electrical insulation, and other items. Plasticizers in surface coatings enhance the flow and leveling properties of the material during application and reduce the brittleness of the dried film. 

TG-DTA-MS has obvious synthetic polymer applications. TA-MS has been appHed to study the thermal behavior of homopolymers, copolymers, polymeric blends, composites, residual monomers, solvents, additives, and toxic degradation products. In the latter context, FICl evolution from heated polyfvinyl chloride) materials is readily quantified by TA-MS and such data are of major significance in the design of fire-resistant polymeric materials. Pyrotechnic materials have been studied by TA-MS. A complex sequence of thermal events relates to the decomposition of these materials involving interactions between the nitrocellulose, perchlorate, and metal components with periodic release of carbon dioxide and oxygen. Only by EGA is it possible to rationalize the thermal behavior of such materials. TA-FTIR has also been applied extensively to study the thermal characteristics of synthetic polymers... 

The shape of the average specimen is such that only rarely can it be directly placed into the diffractometer for analysis, so that special care has to be taken to achieve the random distribution of the crystallites to have meaningful peak intensities. The problems arising in sample preparation are (1) Particle size. The powdered sample must consist of particles smaller than 5 pm. Collection and separation of particles of these dimensions can be effected by sieving, sedimentation, or elutriation. (2) Surface flatness. Special precautions are needed to make the surface smooth and flat, with its plane including the diffractometer axis. If required, common binders, for instance, collodion, paraffin wax, or silicone grease, are applicable. (3) Preferred orientation. When it is necessary to ensure that the particles do not show preferred orientation, mix crushed glass or other amorphous medium with the powder or coat the plane surface of the sample carrier with a film of adhesive that dries at a moderate rate and then dust a layer of powder on the adhesive, polyfvinyl chloride), after it has become tacky. 

Poly(vinyl chloride) has a good resistance to hydrocarbons but some plasticisers, particularly the less polar ones such as dibutyl sebacate, are extracted by materials such as iso-octane. The polymer is also resistant to most aqueous solutions, including those of alkalis and dilute mineral acids. Below the second order transition temperature, polyfvinyl chloride) compounds are reasonably good electrical insulators over a wide range of frequencies but above the second order transition temperature their value as an insulator is limited to low-frequency applications. The more plasticiser present, the lower the volume resistivity. 

The use of a soluble metal-chelating agent such as tetrasodium ethylenediamine tetraacetate effectively stabilizes an anaerobic formulation against small amounts of metal contamination [173]. The wide variety of appUcations of anaerobic adhesives and sealants is made possible by the modifications which make the viscosity appropriate to the application. An application which requires penetration into close fitting parts should have very low viscosity while a product used with large, loose fitting parts should have a high viscosity. Polymethacrylates, cellulose esters, butadiene-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyfvinyl chloride), copolymers of vinyl chloride and vinyl acetate, polyfvinyl acetate), cellulose ethers, polyesters, polyurethanes, and other thermoplastic resins have been used to control the flow characteristics of anaerobic sealants [174]. 

Bromine and chlorine add rapidly to alkenes to yield 1,2-dihalides, a process called halogenation. For example, more than 18 million tons 1,2-dichloroethane (ethylene dichloride) is synthesized worldwide each year, much of it by addition of GI2 to ethylene. The product is used both as a solvent and as starting material for the manufacture of polyfvinyl chloride), PVG. Fluorine is too reactive and difficult to control for most laboratory applications, and iodine does not react with most alkenes. 

Masadome, T., T. Imato, N. Ishibashi, Surfactant-selective electrode ba.sed on plasticized polyfvinyl chloride) membrane and its application. Anal. ScL, 1987,3,121-124. 

---