Page 151 - Handbook of Plastics Technologies

THERMOSETS

THERMOSETS 3.21

TABLE 3.16 Unsaturated Polyester Markets
Market %
Building and construction 26

Corrosion-resistant equipment 20
Shipbuilding and marine 17
Automotive and railroad 13
Consumer products in general 8
Appliances and business machines 6
Electrical 4
Aircraft and aerospace 2

Other 4
Total 100

TABLE 3.17 Polyester Typical Recipe

Material Mols Pounds/pound of resin
Propylene glycol 2.7 0.2564

Maleic anhydride 1.0 0.1225
Phthalic anhydride 1.5 0.2774

Styrene 0.4000
Hydroquinone 0.0001

duce a viscous liquid (50 to 6000 cP), stabilized by hydroquinone. In the second stage, it is
“catalyzed” by organic peroxide ± activators, combined with glass fiber reinforcement,
shaped by a variety of mechanical processes, and cross-linked to produce the finished
product.
In greater detail, during the first-stage reaction, cis-maleic ester isomerizes into trans-
fumaric ester, which luckily is 40× more reactive in the second-stage cross-linking. Propy-
lene glycol may be replaced by neopentyl glycol, trimethylpentane diol, propoxylated or
hydrogenated bisphenol A to increase water and chemical resistance. Maleic/phthalic ratio
may be increased to increase cure rate, hardness, and heat deflection temperature. Phthalic
anhydride may be replaced by isophthalic acid to improve toughness, heat deflection tem-
perature, and water and chemical resistance; or by tetrabromo- or tetrachloro-phthalic an-
hydride or chlorendic acid to increase flame retardance. And styrene may be replaced by
vinyl toluene or diallyl phthalate to reduce volatility; or by triallyl cyanurate or isocyanu-
rate to increase heat deflection temperature.

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