Plastics chemical nature

Depending on the chemical nature of the slurry to be filtered, materials of constmction include wood, plastics, earthenware, steel, lead-lined steel, and brick-lined cast iron. 

The use of flame retardants came about because of concern over the flammabiUty of synthetic polymers (plastics). A simple method of assessing the potential contribution of polymers to a fire is to examine the heats of combustion, which for common polymers vary by only about a factor of two (1). Heats of combustion correlate with the chemical nature of a polymer whether the polymer is synthetic or natural. Concern over flammabiUty should arise via a proper risk assessment which takes into account not only the flammabiUty of the material, but also the environment in which it is used. 

Bags of various constmctions are used in the storage and transportation of dry chemicals. The choice of which type of bag to use should be based on the needs of the product for adequate protection and the requirements of the distribution network. To a certain degree, bags can be custom-made for a particular product indeed, almost any shipping requirement can be satisfied by one of many combinations of paper, plastic, and natural fibers incorporated in the design of bags. 

Plasticization, whether internal (by copolymerization) or external (with additives), is also extremely important for proper performance at the time of apphcation. The ease of coalescence and the wetting characteristics of the polymer emulsion particles are related to their softness and the chemical nature of the plasticizer. 

The processing behaviour of ABS plastics is largely predictable from their chemical nature, in particular their amorphous nature and the somewhat unpleasant degradation products. The main points to bear in mind are ... 

Chemical nature Isolation of casein from milk Production of casein plastics Properties of casein Applications Miscellaneous Protein Plastics Derivatives of Natural Rubber Gutta Percha and Related Materials Shellac... 

Plasticizers can be classified according to their chemical nature. The most important classes of plasticizers used in rubber adhesives are phthalates, polymeric plasticizers, and esters. The group phthalate plasticizers constitutes the biggest and most widely used plasticizers. The linear alkyl phthalates impart improved low-temperature performance and have reduced volatility. Most of the polymeric plasticizers are saturated polyesters obtained by reaction of a diol with a dicarboxylic acid. The most common diols are propanediol, 1,3- and 1,4-butanediol, and 1,6-hexanediol. Adipic, phthalic and sebacic acids are common carboxylic acids used in the manufacture of polymeric plasticizers. Some poly-hydroxybutyrates are used in rubber adhesive formulations. Both the molecular weight and the chemical nature determine the performance of the polymeric plasticizers. Increasing the molecular weight reduces the volatility of the plasticizer but reduces the plasticizing efficiency and low-temperature properties. Typical esters used as plasticizers are n-butyl acetate and cellulose acetobutyrate. 

One of the most common impurities in coastal areas which acts in a chemical manner rather than a physical one is salt water. However, with the ever-increasing spread of the chemical industries, and the stepped-up use of gasoline powered vehicles, the problem of chemical degradation are also of interest particularly in inland areas. While plastics in general are corrosion resistant, the multiplicity of chemical agents which can be in the air in industrial atmospheres, plus the chemical nature of the various plastics indicates that it cannot be assumed that all plastics are chemically resistant to all atmospheres. 

Identification of the chemical nature of a plastics sample is a problem facing processors and users of... 

Levin, B.C., A summary of the NBS litterature Reviews on the chemical nature and toxicity of the pyrolysis and combustion from seven plastics acrylonitrite-butadien-styrenes (ABS), nylons, polyesters, polyetylenes, polysterenes, poly(vinyl-chlorides) and rigid polyurethane foams, KB SIR 85-3267, 1986... 

On heating a chemical reaction took place between the rubber and sulphur which resulted in production of tough elastic rubber that retained its moulded shape. Natural rubber is plastic in nature while vulcanised rubber is elastic. This vulcanisation process led to a rapid development of rubber industry. 

During radiological decontamination efforts, caregivers should consider the chemical nature of the contaminant, the medical needs of the patient, the seriousness and extent of contamination, and the presence of wounds. Prior to implementing decontamination procedures, remove all outer clothing from the contaminated individual and place the clothing in a sealed container such as a plastic bag. Save clothing so... 

At low temperatures, the behaviour depends on the chemical nature, the plasticization and the mechanical constraints undergone. 

The mechanical properties at room temperature depend on the chemical nature and the plasticization. They are generally fair with a low to medium modulus and a low to excellent impact strength, but performances decrease when the temperature rises. 

Throughout the text we will relate polymer structure to the properties of the polymer. Polymer properties are related not only to the chemical nature of the polymer, but also to such factors as extent and distribution of crystallinity, distribution of polymer chain lengths, and nature and amount of additives, such as fillers, reinforcing agents, and plasticizers, to mention a few. These factors influence essentially all the polymeric properties to some extent including hardness, flammability, weatherability, chemical stability, biological response, comfort, flex life, moisture retention, appearance, dyeability, softening point, and electrical properties. 

Dagani, R. 2002. Electrifying plastics. Chemical Engineering News (16 October) 4—5. Dalton, A. B. et al. 2003. Super-tough carbon-nanotube fibers. Nature 423 803. 

Plasticizer analysis Is Indispensable In establishing the purity of technical plasticizers and determining the chemical nature of plasticizers in finished and semi-finished articles. When plastics are used for food packaging and similar purposes, only certain nontoxic substances are acceptable as plasticizers, and this is why health authorities take an active interest In plasticizer analysis. Requirements such as these have promoted the development of analytical methods that are as simple and as time-saving as possible. This article deals with the present art of plasticizer analysis—Its methods and problems—based on the literature as well as on the results of the author s own Investigations. 

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