Polymer products, chemical industry

For more than one reason clay minerals offer a challenge to colloid scientists. From a practical point of view, the wide occurrence In soils and the relevance for agriculture, fertilization and topsoil mechanical properties may be mentioned. Technical applications are encountered in the paper Industry, in ceramics, in brick production, chemical industry and for cleaning purposes ("fuller s earth"). Invariably, these applications Involve clay minerals as the adsorbents for polymers, monomers and/or ions. Double layers around clay particles enter the picture In connection with these adsorption phenomena and... 

The first commercially available acetal resin was marketed by Du Pont in 1959 under the trade name Delrin after the equivalent of ten million pounds had been spent in research or polymers of formaldehyde. The Du Pont monopoly was unusually short lived as Celcon, as acetal copolymer produced by the Celanese Corporation, became available in small quantities in 1960. This material became commercially available in 1962 and later in the same year Farbwerke Hoechst combined with Celanese to produce similar products in Germany (Hostaform). In 1963 Celanese also combined with the Dainippon Celluloid Company of Osaka, Japan and Imperial Chemical Industries to produce acetal copolymers in Japan and Britain respectively under the trade names Duracon and Alkon (later changed to Kematal). In the early 1970s Ultraform GmbH (a joint venture of BASF and Degussa) introduced a copolymer under the name Ultraform and the Japanese company Asahi Chemical a homopolymer under the name Tenal. 

Petrochemicals in general are compounds and polymers derived directly or indirectly from petroleum and used in the chemical market. Among the major petrochemical products are plastics, synthetic fibers, synthetic ruhher, detergents, and nitrogen fertilizers. Many other important chemical industries such as paints, adhesives, aerosols, insecticides, and pharmaceuticals may involve one or more petrochemical products within their manufacturing steps. 

Within the chemical industry, micro-organisms and enzymes are often used as catalysts. It is possible for a unit operation in an essentially chemical production process to be a biochemically catalysed step giving rise to a mixed chemical/biochemical production process. The products of these reactions include organic chemicals, solvents, polymers, pharmaceuticals, and purfumes. Mixed chemical/biochemical production processes are continuously innovated and optimised, mainly for economical reasons. 

Since most polymers, including elastomers, are immiscible with each other, their blends undergo phase separation with poor adhesion between the matrix and dispersed phase. The properties of such blends are often poorer than the individual components. At the same time, it is often desired to combine the process and performance characteristics of two or more polymers, to develop industrially useful products. This is accomplished by compatibilizing the blend, either by adding a third component, called compatibilizer, or by chemically or mechanically enhancing the interaction of the two-component polymers. The ultimate objective is to develop a morphology that will allow smooth stress transfer from one phase to the other and allow the product to resist failure under multiple stresses. In case of elastomer blends, compatibilization is especially useful to aid uniform distribution of fillers, curatives, and plasticizers to obtain a morphologically and mechanically sound product. Compatibilization of elastomeric blends is accomplished in two ways, mechanically and chemically. 

Whether butadiene reacts with itself to give linear polymers or 8- or 12-carbon rings is a function of the catalyst and conditions used. Development of catalysts needed to give the desired products is the job of catalyst research chemists. Although catalysis is critically important in the chemical industry and much work has been done on it in research laboratories for many years, catalyst development remains more of an art than a predictable science, and the chemists involved in this type of research use methods they have learned experimentally, not from books or in classrooms. 

Most small olefins produced in the chemical industry are used to make polymers, with a global production of the order of 100 million tons per year. Polymers are macromolecules with molecular weights of typically lO" to 10 and consist of linear or branched chains, or networks built up from small monomers such as ethylene, propylene, vinyl chloride, styrene, etc. The vast majority of polymers are made in catalytic processes. Here we concentrate on ethylene polymerization over chromium catalysts as an example [M.P. McDaniel, Adv. Catal. 33 (1985) 47]. 

Polymer products synthesized in laboratories and in industry represent a set of individual chemical compounds whose number is practically infinite. Macro-molecules of such products can differ in their degree of polymerization, tactici-ty, number of branchings and the lengths that connect their polymer chains, as well as in other characteristics which describe the configuration of the macromolecule. In the case of copolymers their macromolecules are known to also vary in composition and the character of the alternation of monomeric units of different types. As a rule, it is impossible to provide an exhaustive quantitative description of such a polymer system, i.e. to indicate concentrations of all individual compounds with a particular chemical (primary) structure. However, for many practical purposes it is often enough to define a polymer specimen only in terms of partial distributions of molecules for some of their main characteristics (such as, for instance, molecular weight or composition) avoiding completely a... 

Plastics additives now constitute a highly successful and essential sector of the chemical industry. Polymer additives are a growing sector of the specialty chemical industry. Some materials that have been sold for over 20 years are regarded today as commodity chemicals, particularly when patents covering their use have expired. Others, however, have a shorter life or have even disappeared almost without trace, e.g. when the production process cannot be made suitably economic, when unforeseen toxicity problems occur or when a new generation of additive renders them technically obsolete. 

Applications The broad industrial analytical applicability of microwave heating was mentioned before (see Section 3.4.4.2). The chemical industry requires extractions of additives (antioxidants, colorants, and slip agents) from plastic resins or vulcanised products. So far there have been relatively few publications on microwave-assisted solvent extraction from polymers (Table 3.5). As may be seen from Tables 3.27 and 3.28, most MAE work has concerned polyolefins. 

Some of the challenges facing the industrial laboratory are limited resources, cost containment, productivity, timeliness of test results, chemical safety, spent chemicals disposal, technician capability, analytical capability, disappearing skills, and reliability of test results. The present R D climate in the chemical industry is one of downsizing at corporate level (lean and mean), erosion of boundaries between basic and applied science, and polymer science and analytical chemistry as Cinderella subjects. Difficult chemical analyses are often run by insufficiently skilled workers (a managerial issue). 

The current structure of the chemical industry can be characterized by the different products starting at with oil and gas and with further refinements on the following steps with petrochemicals, basis chemicals, polymers, specialties and active ingredients as shown in fig. 26. 

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