PVC, chlorinated

In chlorinated PVC, the high content of chlorine imparts some favorable characteristics, but also confers other characteristics that are not as desirable, i.e., the rigidity of the molecule impedes its movement and thus it is a material which is more difficult to process, and at the same time it becomes fragile and, as PVC, tends to breakdown under the high temperature conditions required for its processing. 

Examples of lubricants for chlorinated PVC are metal stearates, montan waxes, high and low molecular weight paraffinic waxes, as well as oxidized waxes. Specific examples of external lubricants are Advalube E-2100 available from Rohm and Haas, Licolub XL 445 available from Clariant. These lubricants are used at levels ranging from 4-5.5 phr (8). 

In electrically conductive poly(oxymethylene) (POM) molding compositions special problems with the lubricant composition emerge (9). Only a few lubricants are capable of reducing abrasion when used with conductivity black incorporated into POM. It is likely that they disrupt the bonding between matrix and carbon black. This may well also be the reason for the reduction in mechanical properties. Therefore, careful selection and use of the lubricants is required. 

The electrical conductivity is maintained by the addition of a lubricant mixture composed of a lubricant with predominantly external lubricant action and of a lubricant with predominantly internal lubricant action. 

Preference to the former type has been given to a high-molecular-weight, oxidized and therefore polar polyethylene wax. This improves the tribological performance and can reduce the severity of drop down in mechanical properties. Stearyl stearate is preferably used as an internal lubricant that establishes gentle conditions for the incorporation of the carbon black. 

This chapter has so far dealt with the major fields of use of vinyl chloride polymers, namely plasticised PVC homopolymer, unplasticised PVC, including impact-modified grades, and copolymers particular based on vinyl acetate. There are, however, five particular special forms of vinyl chloride polymer which merit separate consideration, namely crystalline PVC, after-chlorinated PVC (often known as CPVC) and certain graft copolymers and two vinyl-chloride-based copolymers. 

It is interesting to note that these crystalline materials do not dissolve in tetrahydrofuran or cyclohexanone at room temperature, indicating that PVC is too weak a proton donor to overcome extensive crystallisation. Crystalline PVC has a greater tensile strength and creep resistance than conventional polymer. It is, however, brittle, and whilst most conventional impact modifiers appear ineffective, EVA polymers are said to be quite useful. Plasticised compounds may also be prepared although mixing temperatures of up to 190°C are necessary. 

The process of post-chlorinating PVC was carried out during World War II in order to obtain polymers soluble in low-cost solvents and which could therefore be used for fibres and lacquers. The derivate was generally prepared by passing chlorine through a solution of PVC in tetrachloroethane at between 50°C and 100°C. Solvents for the product included methylene dichloride, butyl acetate and acetone. These materials were of limited value because of their poor colour, poor light stability, shock brittleness and comparatively low softening point. 

In the 1960s materials became available which are said to have been obtained by chlorination at lower temperatures. In one process the reaction is carried out photochemically in aqueous dispersion in the presence of a swelling agent such as chloroform. At low temperatures and in the presence of excess chlorine the halogen adds to the carbon atom that does not already have an attached chlorine. The product is therefore effectively identical with a hypothetical copolymer of vinyl chloride and symmetrical dichloroethylene. An increase in the amount of post-chlorination increases the melt viscosity and the transition temperature. Typical commercial materials have a chlorine content of about 66-67% (c.f. 56.8% for PVC) with a Tg of about 110% (c.f. approx. 80°C for PVC). 

The main applications for CPVC arise from the fact that the material has a softening point of about 100% and very good chemical resistance. Particular interest has been shown in waste and soil systems which may pass hot water effluents. Calendered sheet may be vacuum formed for uses where hot filling techniques are employed, for example in jam packing. 

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Dry chlorine has a great affinity for absorbing moisture, and wet chlorine is extremely corrosive, attacking most common materials except HasteUoy C, titanium, and tantalum. These metals are protected from attack by the acids formed by chlorine hydrolysis because of surface oxide films on the metal. Tantalum is the preferred constmction material for service with wet and dry chlorine. Wet chlorine gas is handled under pressure using fiberglass-reinforced plastics. Rubber-lined steel is suitable for wet chlorine gas handling up to 100°C. At low pressures and low temperatures PVC, chlorinated PVC, and reinforced polyester resins are also used. Polytetrafluoroethylene (PTFE), poly(vinyhdene fluoride) (PVDE), and... 

Chlorinated PVC (CPVC) is used in higher temperature apphcations such as hot-water piping. Because of its superior creep resistance, CPVC is also used in automated fire-safety sprinkler systems. 

POLYETHYLENE AND COPOLYMERB CHLORINATED PVC (HIGH VOLTAGE) POLYSTYRENE AND COPOLYMERS POLYPROPYLENE OLEFINIC THERMOPLABTIC RUBBERS... 

Since chlorinated PVC is totally transparent in the near-UV and visible range, it will not absorb at 488 nm, the emission line of the argon ion laser that we intended to use to perform the carbonization. Therefore C-PVC films were first exposed to the UV radiation of a medium pressure mercury lamp in order to produce the strongly absorbing polyenes. This irradiation was carried out at room temperature in the absence of oxygen, thus preventing the formation of undesirable oxidation products. 

Figure 6. IR absorption spectra of chlorinated PVC before and after laser irradiation at 488 nm for 0.1 s in air...

Table I Influence of the beam focusing in the laser-graphitization of chlorinated PVC (continuous wave mode emission line at 488.1 nm of Ar+ laser)...

In the present study it has been shown for the first time that chlorinated PVC can be readily transformed into a conducting polymer by simple laser irradiation in the presence of air. The resulting material consisted essentially of carbon and proved to be able to carry electrons, without any doping procedure. By focusing the laser beam down into the micron range, it becomes thus possible... 

Chlorinated PVC (CPVC), uses of, 25 684 Chlorinated rubber, for corrosion protection, 7 201... 

Chlorinated PVC obtained above 100°C is largely used in adhesive and protective coatings and to make filter cloth for corrosive liquids. 

Poly Vinyl ACetate Poly Vinyl ALcohol PolyVinyl Butyrate Poly Vinyl Chloride PolyVinyliDene Chloride Chlorinated PVC Unplasticized PVC... 

Goethite is used in flame retardants and smoke suppressants. Both laboratory and large scale pilot tests showed that goethite is the most active smoke suppressant when polymers and plastics are burned (Carty and White, 1999 Carty et al., 1999). It reduces the amount of smoke produced during pyrolysis in air of chlorinated PVC plasticized with dioctylphthalate, by changing the decomposition pathway followed by phthalate, so that benzene, which is produced in the absence of the smoke suppressant, is not formed (Carty et al., 1999). 

VC = polyvinylchloride ABS = acrylonitrile butadiene styrene CPVC = chlorinated PVC PVF = polyvinylfluoride. 

Table 4.1 Effect of solvent used for dehydrochlorination of the polymer precursor on pore size distribution in activated carbon. Experimental conditions chlorinated PVC was treated with KOH at 20°C for 5 h thermal treatment conditions carbonization at 400°C for 30 min followed by activation with CO at 900°C for 5 min...

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