Synthetic polymers and rubbers

Wang, C.-Y., Analysis of Synthetic Polymers and Rubbers, Anal Chem. 1997 ... 

Application Reviews, published in alternating years by Analytical Chemistry, includes a section on analysis of synthetic polymers and rubbers in which ah references to specific analytical methods, including hquid chromatography, are grouped together, e.g.. Smith, P. B., et al.. Analytical Chemistry, 1997, 69, 101R-103R. 

In 2002, the world production of polymers (not including synthetic libers and rubbers) was ca. 190 million metric tons. Of these, the combined production of poly(ethylene terephthalate), low- and high-density polyethyelene, polypropylene, poly(vinyl chloride), polystyrene, and polyurethane was 152.3 milhon metric tons [1]. These synthetic, petroleum-based polymers are used, inter alia, as engineering plastics, for packing, in the construction-, car-, truck- and food-industry. They are chemically very stable, and can be processed by injection molding, and by extrusion from the melt in a variety of forms. These attractive features, however, are associated with two main problems ... 

Way back in 1968 Dr. Silver was working for 3M on pressure-sensitive adhesives. These are glues that bond instantly to a surface but can be removed without destroying that surface. Today we are very familiar with such products peel-off stickers are everywhere. In 1968, however, they were virtually unknown. Scientists did realize that certain polymers, like natural rubber, could be peeled off under the right conditions, but they were not ideal. So Silver went to work. He investigated various synthetic polymers and eventually came up with one that was a weak adhesive and could be pulled off a surface. The difficulty was that it would not always pull off cleanly, and Silver lost interest. 

A cellular plaslic has been defined as a plastic the apparent density of which is decreased substantially by die presence of numerous cells disposed throughout its mass, in this article the terms cellular plaslic. foamed plastic, expanded plastic, and plastic foam are used interchangeably in denote all two-phase gas-solid systems in which the solid is continuous and composed of a synthetic polymer or rubber. 

With increasing frequency, the permittivity of dielectric decreases. A major factor in the selection of insulation is the ability of the insulation to resist the absorption of moisture. Moisture, of course, can greatly lower resistivity. For wire insulation, synthetic polymers and plastics essentially have replaced the use ol natural rubber. Usually, prior to coaling a wire with a plastic material, (lie wire must he treated to assure good contact and adhesion of the insulating material. Copper wire, for example, is treated with hydrogen fluoride, which creates a coating ol clipper fluoride in the... 

A recently developed one-step ammonoxidation process to acrylonitrile developed by BP Chemicals uses propane instead of propylene feed [21]. Key to the feasibility of this lower cost option was the development of the new catalyst system, which is now at the commercial demonstration stage. Almost all the acrylonitrile production goes into synthetic polymers and copolymers mostly for applications as fibers, some for plastics applications, and a small percentage to elastomer markets (the nitrile rubbers). 

The applications of TGA are extensive and diverse and include oxy-salt decompositions, natural and synthetic polymer characterization, metal oxidation and corrosion analysis, compositional analysis of coals, polymers, and rubbers, study of glass materials, foodstuffs, catalytic materials, biological materials, and a wide range of chemical processing phenomena. It has been used very successfully to study the kinetics of chemical processes however, there is much controversy surrounding this application, particularly in terms of relating TGA data to reaction kinetics models. 

The polymers which will be studied in this book are synthetic polymers and the industrial importance of such materials is well-known. However, we must recall that there also exist numerous natural polymers, and some of these have a great biological importance. Among the most common ones, we may cite natural rubber extracted from hevea latex and cellulose, with its derivatives, extracted from wood. 

Surface modification is broadly used in controlling the surface properties of fillers in rubber, synthetic polymers and other materials (see Chapter IX). The surfactant adsorption layers that make surfaces hydrophobic are used to prevent caking in hygroscopic powders (fertilizers), as anticorrosive agents and in numerous other processes. 

Bitumen modifiers can be synthetic polymers, natural rubber (latex) and some chemical additives such as sulfur and certain organo-metallic compounds. Fibres and fillers (inorganic powders) are not considered to be bitumen modifiers. Table 3.16 gives some typical bitumen modifiers, as well as significant improvements to asphalts. Polymers are the most common type of bitumen modifiers, with thermoplastic elastomers being the most popular polymer. 

An extremely wide range of materials can be used for building. These can be either natural or man-made. Natural materials include aggregates, bitumen, clays, rubber, stone, and wood man-made materials include brick, inorganic cements, glass, plaster, metals and their alloys, synthetic polymers, and wood preservatives. 

Many applications are being found for synthetic rubbers, which are synthetic polymers possessing rubber-like properties. Among those available commercially are butadiene-styrene and butadiene-acrylonitrile (called Buna rubbers), polyisoprene, and polybutadiene. Their properties may be modified considerably more than vulcanized rubbers, particularly with respect to resistance to oxidizing agents, solvents, and oils. Their adhesion to metals, however, is generally poorer. 

Hayes and Altenau [34] were the first to report the use of MS to directly characterise antioxidants and processing oil additives in synthetic rubbers. Since then, various MS techniques have been applied to the analysis of rubber and polymer additives either as extracts or on the sample surface by laser techniques as reviewed by Lattimer and Harris [35]. Lattimer reviewed the present situation regarding MS in polymer analysis [36]. Analysis of polymer extracts by MS has proved challenging. Electron impact mass spectra (EI-MS) are often difficult to interpret due to the high concentration of processing oils and the additives in the extract, and excessive fragmentation of the molecular ions. Desorption/ionisation techniques such as field desorption (ED) and fast atom bombardment (FAB) have been found to be the most effective means for analysing polymer and rubber extracts [37, 38]. 

The main engineering polymers are polyamides (nylon 6,6 and 6), polycarbonates (bisphenol A-derived), polyphenylene oxides (PS-modified), acetals, polyesters (PETP and poly butylene terephthalate) and polyfluorocar-bons (mainly PTFE). Together with the synthetic elastomers and rubber-modified thermosets they make up the bulk of added-value products. 

One reason that synthetic polymers (including rubber) are so popular as engineering materials is their chemical and biological inertness. On the down side, this characteristic is really a liability when it comes to waste disposal. Most polymers are not biodegradable and, therefore, do not biodegrade in landfills major sources of waste are from packaging. 

High cw-polyisoprene, either natural or synthetic, will remain an essential raw material for the rubber industry because of its combination of high strength and high resilience characteristics coupled with a broad-based utility. Therefore, it is important for rubber technologists to appreciate both the natural and synthetic polymers and to know how to use each to its best advantage. 

Applications. Among the P—O- and P—N-substituted polymers, the fluoroalkoxy- and aryloxy-substituted polymers have so far shown the greatest commercial promise (14—16). Both poly[bis(2,2,2-trifluoroethoxy)phosphazene] [27290-40-0] and poly(diphenoxyphosphazene) [28212-48-8] are microcrystalline, thermoplastic polymers. However, when the substituent symmetry is dismpted with a randomly placed second substituent of different length, the polymers become amorphous and serve as good elastomers. Following initial development of the fluorophosphazene elastomers by the Firestone Tire and Rubber Co., both the fluoroalkoxy (EYPEL-F) and aryloxy (EYPEL-A) elastomers were manufactured by the Ethyl Corp. in the United States from the mid-1980s until 1993 (see ELASTOLffiRS,SYNTHETic-PHOSPHAZENEs). 

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