Polymer flammability toxic gases

Tetrafluoroethylene (TFE), also known as perfluoroethylene, is a colorless, flammable, toxic gas. It is the monomer used for polytetrafluoroethylene (PTFE), which is sold under the DuPont tradename of Teflon. TFE is co-polymerized with other compounds to produce a variety of Teflons. TFE is produced by heating chlorodifluoromethane (CHC1F2, Freon-22) or trifluoromethane (CldF3, Freon-23). TFE is used almost exclusively as a monomer in the production of PTFE. PTFE is a vinyl polymer, which means it is made from a monomer with carbon-carbon double bonds. PTFE is made from TFE by free radical polymerization. 

Synonyms methanal, methylene oxide, oxymethane Formula HCHO MW 30.03 CAS[50-00-0] constitutes about 50% of all aldehydes present in air released in trace quantities from pressed wood products, burning wood, and synthetic polymers and automobiles colorless gas at ambient conditions pungent suffocating odor liquefies at -19.5°C solidifies at -92°C density 1.07 (air = 1) very soluble in water, soluble in organic solvents readily polymerizes flammable, toxic, and carcinogenic (Patnaik, 1992). 

Some of the important factors to consider in the development of alternative physical blowing agents are solubility, permeability, boiling point, vapor pressure, flammability, toxicity, VOC, ODP, GWP, availability, and cost. Similarly, the key important factors to be considered in the selection of CBAs for a given polymer are decomposition temperature, gas yield, rate of gas release, environmentally acceptable decomposition products, toxicity, and dispersability in the polymer matrix. 

The presence of halogen in a polymer produces the most dramatic increase in LOI and decrease in flammability. Thus, rigid (unplasticized) PVC, with a LOI value of 42, has the lowest flammability of any common and many not so common polymers. This advantage is, however, offset by the large amount of smoke and toxic gas (hydrochloric acid) produced when PVC and other chloropolymers bum. Moreover, plasticization of PVC markedly reduces the LOI for example, the value decreases to 25 when 50 phr dioctylphthalate is used as a plasticizer. 

The family of PEN polymers exhibits a good radiation resistance and low flammability and toxic gas emission. The cyano group, because of its polarity, imparts good adhesion properties to glass fibers, therefore the polymers are suitable as a matrix for composite materials. 

Polyetheretherketones (PEEK) have excellent properties for use in advanced polymer composites, including low flammability, low smoke and toxic gas emission, and broad chemical and solvent resistance. PEEK... 

Fluoropolymers also low flammability. The fully fluorinated polymer polytetrafluoroethylene, for example, burns only in 95% oxygen under the test conditions of LOI. The burning, however, produces a highly toxic and corrosive gas hydrogen fluoride. 

In the case of a fire, the development of smoke is of equal importance to the flammability of the plastic. The important factors are density, toxicity and the corrosive effect of the smoke gases. Carbon black increases the density of the smoke gases, the main toxic elements of which are incompletely oxidised carbon, usually in the form of carbon monoxide gas. Crosslinked thermosets generally produce less smoke than most thermoplastics, rather, they tend to carbonise. The polymers that are highly resistant to heat will keep their aromatic or heterocyclic ring structure in the case of fire and carbonise into networks similar to graphite. 

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