Curing of unsaturated polyester resins

Organic peroxides are used extensively for the curing of unsaturated polyester resins and the polymerization of monomers having vinyl unsaturation. The —O—O— bond is split into free radicals which can initiate polymerization or cross-linking of various monomers or polymers. 

Diacyl peroxides are used in a broad spectmm of apphcations, including curing of unsaturated polyester resin compositions, cross-linking of elastomers, production of poly(vinyl chloride), polystyrene, and polyacrjlates, and in many nonpolymeric addition reactions. 

Aromatic diacyl peroxides such as dibenzoyl peroxide (BPO) [94-36-0] may be used with promoters to lower the usehil decomposition temperatures of the peroxides, although usually with some sacrifice to radical generation efficiency. The most widely used promoter is dimethylaniline (DMA). The BPO—DMA combination is used for hardening (curing) of unsaturated polyester resin compositions, eg, body putty in auto repair kits. Here, the aromatic amine promoter attacks the BPO to initially form W-benzoyloxydimethylanilinium benzoate (ion pair) which subsequentiy decomposes at room temperature to form a benzoate ion, a dimethylaniline radical cation, and a benzoyloxy radical that, in turn, initiates the curing reaction (33) ... 

Ketone Peroxides. These materials are mixtures of compounds with hydroperoxy groups and are composed primarily of the two stmctures shown in Table 2. Ketone peroxides are marketed as solutions in inert solvents such as dimethyl phthalate. They are primarily employed in room-temperature-initiated curing of unsaturated polyester resin compositions (usually containing styrene monomer) using transition-metal promoters such as cobalt naphthenate. Ketone peroxides contain the hydroperoxy (—OOH) group and thus are susceptible to the same ha2ards as hydroperoxides. 

Commercially available MEKP formulations are mixtures of the dihydroperoxide (1), where X = OOH R = H, R = methyl, and R = ethyl (2,2-dihydroperoxybutane [2625-67 ]) and dialkyl peroxide (2), where X = OOH, Y = OOH, R = methyl, and R = ethyl (di(2-hydroperoxy-2-butyl) peroxide [126-76-1J). These formulations are widely used as free-radical initiators in the metal-promoted cure of unsaturated polyester resins at about 20°C. 

Pucid, I. and Ranogajec, F. 1995. DC-electrical conductivity as a method for monitoring radiation curing of unsaturated polyester resins. 1. Measurement conditions and comparison with extraction analysis data. Radiat. Phys. Chem. 46 365-370. 

Storage May develop pressure vent bottle periodically Uses Polymerization initiator/catalyst/crosslinking agent for cure of unsaturated polyester resins in gel coats to eliminate or reduce porosity mfg. of acrylic resins hardener for fiberglass-reinforced plastics catalyst in food-contact crosslinked polyesters Regulatory FDA 21 CFR 177.2420... 

Uses Initiator for cure of unsaturated polyester resins... 

Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating vapors Uses Crosslinking agent, initiator for cure of unsaturated polyester resins Trade Name Synonyms Aztec MIKP-LA-M1 t[Aztec Peroxides] Trigonox HM 4tAkzo Nobel http //www.akzonobei.com]... 

Methyl ethyl ketone peroxide (MEKPO) is the typical sort of highly reactive chemical. It is used as a catalyst for the room temperature curing of unsaturated polyester resins and an initiator for polymerization reactions. It is manufactured in the oxidation process of methyl ethyl ketone (MEK) with hydrogen peroxide (H2O2) (Liaw et al., 2(XX)). 

Lee C L, Hirose Y, Nakatsuka T 1975 [The inhibitory effect of Taxus mairei S.Y. Hu heartwood extractives on the curing of unsaturated polyester resin.] Mokuzai Gakkaishi 21 249-256... 

Free-radical initiated copolymerization can be accomplished either by conventional initiation with organic peroxides or hydroperoxides or phytochemically by using a photoinitiator in UV light. A detailed discussion of UV cured systems is outside the scope of this section therefore, only conventional initiation Is discussed here. The conventional curing of unsaturated polyester resins can proceed either by... 

There can be many reasons for deficient curing. There is considerable experience with radical curing of unsaturated polyester resins. 

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