Carbon dioxide permeability polymer composition

Most acrylonitrile-butadiene styrene terpolymer (ABS) is produced as a graft of SAN onto a butadiene polymer backbone. This graft copolymer may be blended with more SAN or acrylonitrile elastomer (NBR) to improve its properties. ABS is more ductile than SAN. The Tt and the heat deflection temperature of ABS vary with the composition, and ABS may have one set of values for the PBD domains and another set for the SAN matrix. The permeabilities of ABS to oxygen, nitrogen, and carbon dioxide are much less than those of hope. 

Polymers. In combination with various metal salts, sorbitol is used as a stabilizer against beat and light in poly(vinyl chloride) (qv) resins and, with a phenolic antioxidant, as a stabilizer in uncured styrene—butadiene mbber (qv) compositions and in polyolefins (see He AT STABILIZERS Olefin polymers Rubber compounding). Heat-sealable films are prepared from a dispersion of sorbitol and starch in water (255). Incorporation of sorbitol in collagen films gready restricts their permeability to carbon dioxide (256). 

In Section I we introduce the gas-polymer-matrix model for gas sorption and transport in polymers (10, LI), which is based on the experimental evidence that even permanent gases interact with the polymeric chains, resulting in changes in the solubility and diffusion coefficients. Just as the dynamic properties of the matrix depend on gas-polymer-matrix composition, the matrix model predicts that the solubility and diffusion coefficients depend on gas concentration in the polymer. We present a mathematical description of the sorption and transport of gases in polymers (10, 11) that is based on the thermodynamic analysis of solubility (12), on the statistical mechanical model of diffusion (13), and on the theory of corresponding states (14). In Section II we use the matrix model to analyze the sorption, permeability and time-lag data for carbon dioxide in polycarbonate, and compare this analysis with the dual-mode model analysis (15). In Section III we comment on the physical implication of the gas-polymer-matrix model. 

Selected applications for polymers, polymer blends, and composites are shown in Tables 13.11,13.12, and 13.13, respectively. In Table 13.9, poly(ethyl-ene terephthalate) (PET) used for soft drink containers incorporates a bit of comonomer to reduce crystallinity just to the incipient point, rendering it optically clear for esthetic purposes. Most important, PET has an exceedingly low permeability to carbon dioxide (see Section 4.4), allowing for a relatively long shelf life of the sodas. The crystalline homopolymer makes the fiber widely known as polyester. 

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