Partially Halogenated Polymers

The recent studies of partially halogenated polymers described in the previous sections were undertaken to obtain GI POFs with sufficiently low attenuation at specific light source wavelengths at a relatively low cost. These polymers can be categorized as intermediate materials between PMMA and CYTOP on the basis of their performance and material cost, both of which meet the current demand. 

Hence, it is apparent that certain inorganic tin compounds are very effective flame retardants and smoke suppressants for halogenated polymer formulations. Since these additives are generally non-toxic, their potential use as partial or total replacements for existing commercial flame retardants, such as antimony trioxide, is thought to merit serious consideration. 

Halogenated polyolefins form another class of polymers. Some of the polymers from this class have important practical applications. Among these are poly(vinyl chloride), poly(vinylidene chloride), and polytetrafluoroethylene. Several unusual polymers such as poly(vinyl bromide) also are included in this class. Most halogenated polymers are obtained by the polymerization of a halogenated monomer. However, chemical modification (e.g. chlorination) of a preexistent polymer also can be applied to obtain partially halogenated materials. 

PVP is a nonionic water-soluble polymer that interacts with water-soluble dyes to form water-soluble complexes with less fabric substantivity than the free dye. Additionally, PVP inhibits soil redeposition and is particularly effective with synthetic fibers and synthetic cotton blends. The polymer comprises hydrophilic, dipolar imido groups in conjunction with hydrophobic, apolar methylene and methine groups. The combination of dipolar and amphiphilic character make PVP soluble in water and organic solvents such as alcohols and partially halogenated alkanes, and will complex a variety of polarizable and acidic compounds. PVP is particularly effective with blue dyes and not as effective with acid red dyes. 

The polymer has very high tensile strength, an Underwriter s Laboratories (UL) temperature index of 170°C, flame resistance, and low smoke emission. The polymer is resistant to alcohols, acids, and hydrocarbon solvent but will dissolve in partially halogenated solvents. Both glass- and carbon fiber-reinforced grades are available. 

All polymers presented in this section have a common molecular structure, which induces a semicrystalline morphology. They are different from other vinyl polymers whose mechanical properties are similar to those of their amorphous state. The partial crystallinity of these halogenated polymers has to be considered with their glass transition temperature, which is lower than the ambient temperature for most of them. Moreover, they have at least one halogen atom in each monomer unit and hence they are flame-resistant. 

Liquids and polymer surfaces can include three types of hydrogen-bonding molecules (a) proton acceptors (electron donors or bases) such as esters, ketones, ethers or aromatics including polymers such as PMMA, polystyrene, copoly(ethylene vinyl acetate), polycarbonate (b) proton donors (electron acceptors or acids) such as partially halogenated molecules, including polymers such as PVC, chlorinated polyethylenes or polypropylenes, poly(vinylidene fluoride) and copoly(ethylene acrylic acid) and (c) both proton acceptors and proton donors such as amides, amines and alcohols, including polyamides, polyimides and poly(vinyl alcohol). 

Grades of polyisobutylene, butyl mbber, halogenated butyl mbber, and partially cross-linked isobutylene—isopiene—divinylbenzene terpolymer have been developed to meet specific processing and property needs. Recently, two new polyisobutylene-based elastomers have been developed. One is now available commercially as Exxon SB Butyl Polymers (32) and the other is under market development as Exxon bromo XP-50. 

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