Chlorofluorocarbon plastic

Among materials suitable for gaskets are Teflon, Kel F, and other appropriate fluorocarbon or chlorofluorocarbon plastics. Most plastics become embrittled in boron trifluoride service. The use of polyvinyl chloride should be avoided. 

Production of hydrogen fluoride from reaction of Cap2 with sulfuric acid is the largest user of fluorspar and accounts for approximately 60—65% of total U.S. consumption. The principal uses of hydrogen fluoride are ia the manufacture of aluminum fluoride and synthetic cryoHte for the Hall aluminum process and fluoropolymers and chlorofluorocarbons that are used as refrigerants, solvents, aerosols (qv), and ia plastics. Because of the concern that chlorofluorocarbons cause upper atmosphere ozone depletion, these compounds are being replaced by hydrochlorofluorocarbons and hydrofluorocarbons. 

Experience with chlorofluorocarbons (CFCs), insecticides such as DDT, herbicides and fertilizers has taught us that extended stability of these products may lead to unexpected harmfiil results. An important challenge will be to develop novel products that have a limited stable life and then decompose so that they do not persist in this environment. Examples are the development of plastic packages that decompose and degrade with time and of agricultural chemicals that do not harm unintended targets and are not overly persistent. 

Chlorine is used to make plastics such as neoprene and polyvinyl chloride (vinyl). It is used to make insecticides, fireworks, explosives, and paint pigments pharmaceuticals, chloroform, and chlorofluorocarbons (ClFCs) and chlorohydfocarbons (ClHCs). 

In 1974, F. Sherwood Rowland and Mario Molina, who shared the 1995 Nobel Prize in Chemistry with Crutzen, showed that chlorine from photolyzed chlorofluorocarbons (CFCs) such as CF2C12 and CFCI3, which were used as supposedly inert refrigerants, solvents for cleaning electronic components, plastic foam blowing agents, and aerosol spray propellants, can also catalyze ozone loss. Subsequently, the chlorine monoxide molecule CIO, which is involved in the chlorine-catalyzed ozone destruction cycle, has been shown to be present in the holes in the ozone layer and to correlate inversely with... 

Chlorine can be substituted by hydrogen fluoride and boron trifluoride to yield chlorofluorocarbon compounds. This process is applied for producing 1,1-dichloro-l-fluoroethane (14), which is considered as a replacement for trichlorofluoromethane as a blowing agent for plastic foam.18... 

Chlorofluorocarbons (CFCs) are widely used in refrigeration and air conditioning, insulation, and plastic foams. Although nontoxic and nonflammable, they are believed to deplete the ozone layer in the atmosphere which shields the earth from the sun s ultraviolet radiation. While action to control the production and use of CFCs was still being debated, McDonalds s Corporation announced it would no longer use foam food containers produced with the aid of CFC in its fast food outlets. 

In 1985 large holes were discovered in the ozone layer over Antarctica, Australasia and Europe (Figure 7.12). Scientists think that these holes have partly been produced by chemicals called chlorofluorocarbons or CFCs. CFCs were developed as refrigerants in fridges back in the 1950s. They have also been used in air conditioning systems, in aerosol cans (as propellants) and in the manufacture of expanded plastics such as polystyrene. CFCs are very unreactive molecules. They escape into the atmosphere and, because of their inertness, remain without further reaction until they reach the... 

Carbon tetrachloride 4 X X Production of chlorofluorocarbon refrigerants and foamblowing agents solvents manufacture of paints and plastics metal cleaning solvent fumigants 111,351,3521, 354, 38... 

Most people are familiar with CFCs (chlorofluorocarbons) and how they eventually became doomed as an input into modern industrial products. Ironically, these compounds were initially introduced as environmentally perfect alternatives due to their nontoxic and nonbioaccumulative nature. This is one of many examples of decisions - in this case about safe materials - that have been made on large scale, only to be followed by a late awakening and significant costs to society and individual organizations. Some of the more recent examples now looming on the horizon may be even worse due to their direct impacts on humans - antibiotic-resistant strains of microbes from antibiotics in biota, hampered kidney function from cadmium in foods, and endocrine disruption from plastic additives, to mention just a few. 

Chlorofluorocarbons were complefely removed from plastic foam products for food packaging, such as egg cartons and meat trays in the early 1990s currently, HCFC-22 mixed with carbon dioxide, HFCs, supercritical fluids, pentane, or isopentane is being used as an alternative. Dow Chemical has reported that it uses HCFC-142b in its polystyrene and polyethylene fabricated foams. ... 

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