Chlorinated polyethylene chlorine content

Chlorinated Polyethylene. Chlorinating polyethylene under pressure results in a polymer having a chlorine content varying from 25 to 42%. The polymer requires the incorporation of carbon black and minerals for achieving good physical properties. The polymers handle like conventional polymers and can be mixed and processed on conventional mbber equipment. 

DuPont have produced a modified chlorosulphonated polyethylene based polymer (trade name Acsium). In this modified polymer the chlorine content is reduced, but an additional pendant alkyl group is used to restrict the ability of the polymer to crystallise. The result is a polymer with a lower Tg than the conventional CSM polymer. 

Due to the chlorine content, oxygen indices are higher than those of the polyethylenes, for example 23 to 25 without fire-retardant additives, but they will act as a combustible material in the event of fire. Combustion products include hydrochloric acid and carbon monoxide, both toxic gases. 

Pure PVC is the linear homopolymer of vinyl chloride, as we can see in Figure 4.32. The industrial polymers are amorphous with a backbone identical to those of polyethylene, polypropylene and polybutene but the pendant chlorine atoms result in a polar polymer. The theoretical chlorine content is roughly 57%. 

The insertion of a certain amount of chlorine atoms into the unit cells of polyethylene and of isotactic polypropylene has been observed by PLATfe, Tran Kheu, and Shibaev (75) by chlorination of the pure homopolymers. The unit cell constants of the two pure homopolymers increase with increasing amount of bound chlorine. The amorphisation of polyethylene is reached with a chlorine content of about 50%. 

Analogous behavior was observed by Oswald and co-workers (12) for blends of chlorinated polyethylene with a high chlorine content when the difference between the Tg s of the two components was greater than 30°C. In our case the values of ATg are about 45° (E13) and 34°C (E14) in regard to the homopolymer PVC. 

Fig. H. Plots of tan 8 against temperature for blends of chlorinated polyethylene (44 % Cl) with chlorinated polyethylene (66% Cl) 1 pure CPE (66% O) 2 87.0% 3 73.5% 4 50.0% 5 25.0% and 6 11.0% of CPE (66 % Cl) in CPE (44 % O) 7 pure CPE (44% Cl). The inset shows a plot of T against weight percent of the chlorinated polyethylene with the higher chlorine content, there is no marked deviation from linearity which is the expected result for systems with no specific interaction...

Fig. 17. The miscibility of chlorinated polyethylenes with others having a different chlorine content, (—) miscible (+) immiscible. Group C includes mixtures of rubbery polymers with glassy polymers and group D is generally mixtures of rubbery polymers with the largest differences in chlorine content. These two groups give the largest (unfavourable) equation-of-state contributions to the fiee energy of mixing...

Fig. 18. A plot of the minimum of the cloud point curve against chlorine content for blends of chlorinated polyethylene with ethylene-vinyl acetate copolymers having A (40 % vinyl acetate), B (45 % vinyl acetate). It is seen that the higher concentrations of interacting groups, CHCl or C=0, give a larger temperature range of miscibility...

When polyethylene is chlorinated, chlorine replaces hydrogen at random. The softening point of this chlorinated product depends on the chlorine content. It is found that small amounts of chlorine (10 to 50 wt% Cl) lowers the softening point while large amounts ( 70%) raise the softening point. Rationalize this observation on the basis of intermolecular forces. 

Aliphatic chlorine flame retardants are represented by chloroparaffins, with chlorine content between 40 and 70%. They typically have a poor thermal resistance, as their dechlorination often starts at 180°C (356°F) hence, their application is restricted by polyethylenes and PVC. 

Chlorinated polyethylene (CPE) flexibilizes and toughens PVC more by a miscibility mechanism especially when the chlorine content is above 42% [Donbe and Walsh, 1979]. However, partial miscibility occurring at chlorine levels of 36% leads to higher toughening effects. CPE offers also weatherability advantage, which is the major reason for its commercial use. 

To manufacture chlorinated rubber (CR) natural or synthetic rubber such as polyethylene, polypropylene or polyisoprene is degraded to low molecular mass compounds by mastication or addition of radical formers and dissolved in carbon tetrachloride (CTC). Chlorine contents are typically 64-68 wt%. Chlorine gas is introduced into this solution and reacts with the raw material to form CR. The solution is then introduced into boiling water. The CR is precipitated, and the solvent vaporizes. The CR is separated from water, rinsed, dried and ground to form a white powder which is the saleable product. After removal of the water, chlorine, hydrochloric acid and other impurities the solvent is reused. 

Chlorinated Polyethylene and Polypropylene. Totally chlorinated polyethylene and polypropylene have a chlorine content of 64 68%. Their properties largely correspond to those of chlorinated rubber (see Section 2.3). Chlorinated polypropylenes can be used for chemical-resistant and weather-resistant coatings. These binders are important in adhesion priming coats and heat-sealing lacquers for polypropylene foils. 

In the absence of oxygen, the chlorination of polyethylene, with or without a catalyst, can be controlled to provide products with varying chlorine content. The chlorination process is statistically random so that chlorination of polyethylene to the same chlorine content as poly(vinyl chloride) (60%) gives a product that is chemically different from PVC yet fiilly compatible with it. This random chlorination of polyethylene destroys its crystallinity. At a degree of chlorination corresponding to the loss of all its crystallinity, the chlorinated product becomes soluble at room temperature. The p-bromination of polyethylene follows a similar course to yield a rubberlike polymer at 55% bromine content. 

Chlorinated polyethylene (CPEy PEC). With a chlorine content to 25 to 40%, its most important applications are in PVC as an impact modifier and in technical rubber goods. Trade names Dow CPE (USA), Hostalit Z (FRG), Hostapren (FRG). 

Solid grades with high chlorine content are used in thermoplastics such as low-density polyethylene (LDPE) in cable jacketing in combination with Sl>203. 

Chlorosulfonated polyethylene is a saturated chlorohydrocarbon rubber produced from CI2, SO2, and a number of polyethylenes, and contains about 20 to 40% chlorine and 1 to 2% sulftir as sulfonyl chloride. Sulfonyl chloride groups are the curing or cross-linking sites.2 CSM properties are largely based on initial polyethylene (PE) and percent chlorine. A free-radical-based PE with 28% chlorine and 1.24% S has a dynamic shear modulus range from 1000 to 300,000 Ib/in (7 MPa to 2.1 GPa). StiflEhess differs for free-radical-based PE and linear PE, with chlorine content at about 30%, CI2 free-radical-based PE stiffness decreases to minimum value, and at about 35%, CI2 content linear PE stiffness decreases to minimum value. When the CI2 content is increased more than 30 and 35%, respectively, the stiffness (modulus) increases.23... 

PMMA/PVC blends provide heat resistance and chemical and flammability resistance into materials for injection moulding and extrusion applications. The major applications of these blends are interior panelling, trim and seat backs in mass transit vehicles. Commercially available PMMA is miscible with PVC [28, 31]. However, its phase behaviour is considered to be only partially miscible [29]. Chlorinated polyethylene blends with PVC have been used as impact modifiers and as secondary plasticisers [32], Chlorine contents of 42% and 30% by weight lead to miscible and immiscible properties, respectively. Impact modification will generally require phase separation, and plasticisation will require miscibility. 

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