Additives acetal resins

A variety of other additives may be incorporated during finishing extmsion to produce acetal resins especially formulated to enhance certain characteristics for specific appHcations. 

The electrical insulation properties of the acetal resins may be described as good but not particularly outstanding. There are available alternative materials which are better insulators and are also less expensive. There are, however, applications where impact toughness and rigidity are required in addition to good electrical insulation characteristics, and in these instances acetal resins would be considered. Table 19.3 lists some of the more important electrical characteristics of Delrin acetal resin. Data for the trioxane-based copolymer resin (e.g. Celcon) are virtually identical. 

Since acetal resins are degraded by ultra violet light, additives may be included to improve the resistance of the polymer. Carbon black is effective but as in the case of polyethylene it must be well dispersed in the polymer. The finer the particle size the better the ultra violet stability of the polymer but the poorer the heat stability. About 1.5% is generally recommended. For white compounds and those with pastel colours titanium dioxide is as good in polyacetals as most transparent ultraviolet absorbers, such as the benzophenone derivatives and other materials discussed in Chapter 7. Such ultraviolet absorbers may be used for compounds that are neither black, white nor pastel shade in colour. 

It should also be mentioned that stearic acid or graphite is some times added in small amounts as an additive to smoke compositions. These materials serve as a lubricant, which really helps reduce sensitivities (especially to friction and impact) of smoke mixes. As for pyrotechnic binders in smokes, vinyl alcohol acetate resin (VAAR) has been used in the past. The most commonly used binder system now in smokes is polyvinyl alcohol (PVA), and it is applied wet. 

Use Manufacture of acetone, acetic acid, acetates, mordant in dyeing and printing of textiles, stabilizer in resins, additive to calcium soap lubricants, food additive (as antimold agentin bakery goods, sausage casings), corrosion inhibitor. 

Chain Scission with Depropagation. Many carbon-chain polymers and other simple chains, such as acetal resins (polyethers), are produced by chain reaction polymerization, either via double bonds or by ring opening. Such polymerizations involve repeated addition of a monomer molecule to an active center, which may be a radical, an ion, or a coordination complex. 

Darvan Dispersing agents, Vanderbilt Dechlorane Plus Fire-retardant additive. Occidental D.E.H. Epoxy catalyst resins, Dow Delrin Acetal resin, DuPont Delrin ST Tough acetal homopolymer, DuPont D.E.N. Epoxy novolac resins, Dow Derakane Epoxy vinyl ester resins, Dow... 

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