Polymer selection, chemical protective

Selection of polymers used in the manufacture of chemical protective clothing (CPC) is a complex task. It involves evaluating breakthrough times and permeation rates in conjunction with such task requirements as tactility and resistance to cuts and abrasion. But, it involves a more basic problem — that of deciding which polymer(s), in the absence of test data, might be most likely to resist permeation by a specific chemical. These decisions are faced not only by users of CPC (e.g., industrial hygienists), but also by poljnner chemists and CPC manufacturers. 

Chemical class searches can be helpful when making selections of materials for use with chemicals which have not been tested for permeation. By extrapolating the information provided by the program for a chemical class, one can (with caution) often select materials that will have better protective qualities than those material selected without this information. However, the uncertainties illustrated from the data in Table I are inherent in any polymer selections made this way. 

No chemical protective suit material resists permeation by all chemicals. These materials are likely to be vulnerable to one or more classes of chemicals. To detect these vulnerabilities, work was started in the 1980s to define a standard battery of test chemicals. The original proposals were based on solubility parameters, which attempts to characterize solvent and polymer interactions. While this provided some insight, eventually a list of 21 chemicals was selected, which represents multiple chemical classes that are generally the smallest molecules in their class, are readily available, and reasonably easy to handle in a laboratory. These chemicals were chosen to give a wide range... 

Nevertheless, professional industrial hygienists are called upon routinely to select protective clothing that will provide an adequate, if not absolute, level of protection, even when permeation data are not available for a specific chemical/polymer combination. Their task is formidable. It is also a task that can be performed more easily with the assistance of an expert system. 

The selective alkylation of a chemically distinct phenohc site on a perfluorinated aromatic has been achieved following a polymer assisted solution phase protection of an alternative o-hydroxybenzoic acid unit as the dioxin-4-one (19) (Scheme 2.45) [66]. A diverse set of 22 different alkyl and benzyl bromides were then attached to the free phenol using cesium fluoride as the base, followed by treatment with Amberlyst 15 and Amberlyst A-21 as the work-up. Subsequent hydrolysis of the dioxin-4-one group with NaOH proceeded smoothly and was quenched... 

The polymer materials not only act as supports for the dye and other necessary additives in the sensing phase, providing protective covering for the transduction element polymers also play various roles in chemical sensors. They provide a compatible environment for the indicator molecules, maintaining or improving the appropriate photophysical features (compared to those observed in homogeneous solution) on which the sensing principle is based. In many cases they collect and concentrate the analyte molecules on sensor surfaces. In addition, the polymer can play an important role in the sensitivity and selectivity of an optical sensor, and its interactions with indicator and analyte molecules influence the analytical performance of the device. 

In the near future, the use of multifunctional polymer-based materials with separation/selective transport capabilities is also to be expected in the design of production systems with integrated environmental protection or inthe combination of chemical reactions and separation by attaching a catalytic functionality to the respective material [1]. Thus, those multifunctional materials should contribute materially to the development of clean energy and/or energy saving and therefore sustainable production technologies. In connection with these perspectives, there is considerable interest in new/modified polymer-based materials with tailored transport/catalytic properties. Also, many sensor applications are based on controlled permeation. 

Vinyl lacquers are used mainly where a high degree of chemical resistance is required these lacquers are based on vinyl chlorides and vinyl acetates. Acrylic lacquers are based on methyl methacrylate and methyl acrylate polymers and copolymers. Other esters of acrylic and methacrylic acid also may be used to make nonconvertible film formers. Judicious selection of these acrylic acid or methacrylic acid esters allows one to produce film formers with specifically designed properties such as hardness, flexibility, gloss, durability, heat, and chemical resistance. Acrylic lacquers, however, are not noted for their water resistance. The principal uses of acrylic-type lacquers are fluorescent and metallic paints, car refinish applications, clear lacquers and sealers for metals, and protective coatings for aircraft components and for vacuum-deposited metals, as well as uses in pigmented coatings for cabinets and appliances. 

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