CHEMICAL COMPOUNDS polyvinyl chloride

High-purity grades of trichloroethylene are used as a feedstock in the synthesis of the refrigerant hydrofluorocarbon 134a. In this process, the trichloroethylene molecule is destroyed to form the new fluorinated compound. It also is used in the production of such chlorinated end products as polychlorinated aliphatics and flame-retardant chemicals. In polyvinyl chloride (PVC) manufacture, trichloroethylene is used as a molecular weight control agent. 

A vast number of polymer compounds are available commercially. Generally they are known by their polymer type in full or abbreviated (e.g., acrylic, polyvinyl chloride or PVC, high density polyethylene or HDPE), and frequently by a manufacturer s trade name. There is little standardisation into classes based on chemical composition or physical performance, as there is for metals. In reality, a particular chemical composition does not fully define the physical properties, while each class of performance properties can be met by a range of competing polymer types. The current trend is towards further diversification polymer compounds are increasingly being tailored to a particular application. Only in industries where recycling is an issue is there pressure for a more limited number of polymers, which can be identified and separated at the end of product life. 

Before the mechanism of vinyl polymerization was understood, the question of the structure of vinyl polymers was of considerable interest. Staudinger had written these polymers as having a head-to-tail arrangement of recurring units, but he had not really furnished evidence of the structure. As Carothers once said, Staudinger had assigned the structure by pronouncement. He was as usual correct, and chemical evidence was developed to establish such structures. For example, when monovinyl methyl ketone polymerized, it could produce by head-to-head, tail-to-tail reaction a 1,4-diketone. By head-to-tail polymerization it would give a 1,5-diketone. These two types have different reactions. The study of the polymer proper showed that the polymer was a 1,5-diketone. In the case of polyvinyl chloride, a head-to-head, tail-to-tail polymerization would lead to a 1,2-dihalide compound, and a head-to-tail polymerization would lead to a 1,3-dihalide. 

The products of the chlor-alkali process are all useful. Sodium hydroxide is used to make soaps and detergents. It is widely used as a base in many other industrial chemical reactions, as well. The hydrogen produced by the chlor-alkali process is used as a fuel. Chlorine has many uses besides water treatment. For example, chlorine is used as a bleach in the pulp and paper industry. Chlorine is also used in the manufacture of chlorinated organic compounds, such as the common plastic polyvinyl chloride (PVC). 

Chemical/Physical. Pyrolysis of di-n-butyl phthalate in the presence of polyvinyl chloride at 600 °C gave the following compounds indene, methylindene, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, biphenyl, dimethylnaphthalene, acenaphthene, fluorene, methylace-naphthene, methylfluorene, and six unidentified compounds (Bove and Dalven, 1984). 

Chemical/Physical. In a laboratory experiment, it was observed that the leaching of a vinyl chloride monomer from a polyvinyl chloride pipe into water reacted with chlorine to form chloroacetaldehyde, chloroacetic acid, and other unidentified compounds (Ando and Sayato, 1984). 

Polyvinyl chloride is processed into a number of forms by including additives. Additives are used to vary the properties of PVC so that it can be made soft and flexible or hard and rigid. Additives are also used to inhibit decomposition as a result of exposure to sunlight, ozone, and chemicals. Plasticizers are the primary additive included in PVC materials. Di(2-ethylhexyl) phthalate (DEHP) and a host of other phthalates are the most common plasticizers. Plasticizers impart flexibility, thermal stability, strength, and resilience to PVC compounds. PVCs without plasticizers are classified as UPVC the letters stand for unplasticized polyvinyl chloride. UPVC is rigid and used for conduit, containers, gutters, and floor tiles. Other common PVC additives are biocides, lubricants, and pigments. 

Chlorine gas is produced by the electrolysis of brine (sodium chloride) in Castner-Kellner cells (first operated in 1886), the main purpose of which is the production of sodium hydroxide solution. Williams (1972, p98) reports that the extent to which the Castner-Kellner process was worked in Britain depended on the ability to dispose of the chlorine. In this light the production of chlorinated organic compounds can be seen as a response to the need to use chlorine. The argument that we need to produce chlorinated organic compounds to use up chlorine was indeed put to me by manufacturers of polyvinyl chloride (PVC) at a DETR-organized seminar on the lifecycle assessment of PVC in July 2001 PVC is the only product made in sufficient quantities to use up all the chlorine produced by other processes. This suggests that if a particular use of a chemical is stopped, because there is a better (less hazardous) way of achieving that purpose, it will have knock-on effects on the availability of chemicals that are co-produced... 

Among the emerging pollutants of industrial origin, Bisphenol A [2,2 bis(4-hydroxydiphenyl)pro-pane] (BPA) has special relevance since it was one of the first chemicals discovered to mimic estrogens as endocrine disrupters.147 This compound was first reported by Dianin in 1891.1411 BPA is produced in large quantities worldwide, mainly for the preparation of polycarbonates, epoxy resins, and unsaturated polyester-styrene resins.149 The final products are used in many ways, such as coatings on cans, powder paints, additives in thermal paper, in dental composite fillings, and even as antioxidants in plasticizers or polymerization inhibitors in polyvinyl chloride (PVC). To a minor extent, BPA is also used as precursor for flame retardants such as tetrabromobisphenol A or tetrabromobisphenol-S-bis(2,3-dibromopropyl) ether.150 This substance can enter the environment... 

Sodium hydroxide has many different uses in the chemical industry. Considerable amounts are used in the manufacture of paper and to make sodium hypochlorite for use in disinfectants and bleaches. Chlorine is also used to produce vinyl chloride, the starting material for the manufacture of polyvinyl chloride (PVC), and in water purification. Hydrochloric acid may be prepared by the direct reaction of chlorine and hydrogen gas or by the reaction of sodium chloride and sulfuric acid. It is used as a chlorinating agent for metals and organic compounds. 

Polyvinyl chloride (PVC) A thermoplastic material composed of polymers of vinyl chloride a colorless solid with outstanding resistance to water, alcohols, and concentrated acids and alkalis. It is obtainable in the form of granules, solutions, lattices, and pastes. Compounded with plasticizers it yields a flexible material superior to rubber in ageing properties. It is widely used for cable and wire coverings, in chemical plants, and in the manufacture of protective garments. 

Veith, G.D., Macek, K.J., Petrocelli, S.R., Carroll, J. (1980) An evaluation of using partition coefficients and water solubility to estimate bioconcentration factors for organic chemicals in fish. In Aquatic Toxicology, pp. 116-129. ASTM STP 707, Eaton, J.G., Parrish, P.R., Hendricks, A.C., Eds., pp.116-129. Am. Soc. for Testing and Materials, Philadelphia, Pennsylvania. Verhoek, P.H., Marshall, A.L. (1939) Vapor pressures and accommodation coefficients of four non-volatile compounds. The vapor pressure of tri-ra-cresyl phosphate over polyvinyl chloride plastics. J. Am. Chem. Soc. 61, 2737-2742. 

Ludovice, Jaffe, and Yoon have used the same approach to characterize the inter- and intramolecular energy surface of polyvinyl chloride (PVC) model compounds.2-Chloropropane and 1,3-dichloropropane were studied, and a classical force field was fitted to their quantum chemically derived energy surfaces. The ultimate goals were to obtain a new force field for molecular mechanics and stochastic dynamics simulations and to analyze the atomic level morphology of this particular polymer. 

With the war years, polyvinyl chloride (PVC) resins came under study, and plasticized PVC compounds, based on these resins, became available as calendered sheet lining materials-the material of choice for stainless steel pickling and for chrome plating and other exposure employing mixtures of chemicals including such strong oxidants as nitric and chromic acid which rapidly attack natural rubber. (A higher temperature limit modification now seldom seen is PVDC, for which the continuous temperature limit is said to be 170°-180°F.)... 

This substance has extensive lipid solubility and is absorbed immediately by the skin. Additionally, DMM is able to penetrate many materials including plastic and rubber compounds such as latex, polyvinyl chloride, and neoprene in a matter of seconds. In permeability tests, a Silver Shield glove of a flexible, plastic-laminate, offered skin protection from DMM for 4h. This chemically resistant glove, when worn under an outer glove that is resistant to abrasion and tears, may provide limited protection for direct handling of DMM. 

Plastic pipes are polymeric in nature (e.g., polyvinyl chloride). Within the pipe are traces of the monomers used in the manufacture of the pipe (e.g., vinyl chloride). In addition, there are a variety of other chemicals added during the manufacture of the pipe as lubricants to facilitate their manufacture or stabilizers to prevent the breakdown of the pipe. In Europe, lead has been used as the stabilizer for pipes, whereas various organic tin compounds have been utilized in the United States. Lead is widely recognized as being toxic. Inorganic tin has a very limited toxicity, but this is not the form of tin that is used. Some of the organic tin compounds are potent nervous system toxins (e.g., trimethyl or triethyl tin), while others appear to adversely affect the immune system (dioctyl tin). The forms of tin used in polyvinyl chloride pipe, however, are primarily monomethyl and dimethyl tin, which are much less active as neurotoxins than the trimethyl tin. There will be some extraction of all these chemicals from the pipe when it is first put into service. However, the concentrations that are found in the water decrease sharply with continued use of the pipe. This is only partially due to the depletion of the chemical from the pipe because continuous water flow will form an impermeable barrier (e.g., calcium carbonate) on the interior of the pipe that minimizes leaching from its surface. 

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