Unsaturated polyester crosslinking agent

Unsaturated polyesters that are terminated by carboxylic acid groups at both ends of the chain after neutralization are efficient emulsifiers for lipophilic monomers [110] and thus act as self-emulsifying crosslinking agents in the ECP of these systems. Normal emulsions of EUP and comonomers have a white, milky appearance. With an appropriate structure and molar mass of the EUP and within a certain range of EUP/comonomer ratios, however, microemulsions are... 

BPO A radical polymerization initiator for vinyl monomers besides, BPO is used as a curing agent for unsaturated polyester resins or a crosslinking agent for saturated polymers. 

Crosslinking - Reaction or formation of covalent bonds between chain-like polymer molecules or between polymer molecules and low-molecular compounds such as carbon black fillers. As a result of crosslinking, polymers such as thermosetting resins may become hard and infusible. Crosslinking is induced by heat, UV or electron-beam radiation, oxidation, etc. Crosslinking can be achieved either between polymer molecules alone as in unsaturated polyesters or with the help of multifunctional crosslinking agents such... 

Other examples of this phenomenon include residual crosslinking agents from partially cured duroplastics, formaldehyde from phenolic resin, amines in epoxy resins, and benzoyl peroxide from unsaturated polyesters. Section 5.3 in chapter Processing (Primary Forming) of Plastics into Structural Components addresses the nitrosamine in elastomers. 

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... 

NFPA Health 3, Reactivity 2 Uses Catalyst/initiator for vinyl polymehzations and for curing unsaturated polyester resins free radical generator blowing agent for plastics esp. for PVC prod, of floats, buoys polymerization catalyst for paper/paperboard in contact with aq.ffatty foods catalyst in food-contact crosslinked polyesters in food-pkg. adhesives... 

Uses Med.-temp. initiator for polymerization of vinyl monomers and the curing of styrene-unsaturated polyester resin compositions crosslinking agent for unsat. polyesters catalyst in premix polyester BMC, SMC Manuf./Distiib. Akzo Nobel http //www.akzonobel.com] Atofina http //www.atofinachemicals.com] Aztec Peroxides Norac http //www.norac.com Trade Name Synonyms Aztec TBPEH t[Aztec Peroxides] Aztec TBPEH-30-AL t[Aztec Peroxides] Esperox 28 [Crompton/Olefins Styrenics] Luperox 26 [Atofina SA http //www.atofina.com] Atofina http //www.atofinachemicals.com]] Perbutyl O t[NOF http //www.nof.co.jp]... 

Uses Polymerization catalyst, initiator, curing agent for polymerization of various ethylenically unsaturated resins and monomers crosslinking agent for polyester bleaching pharmaceuticals Manuf./Distrib. Norac http //www.norac.com Trade Name Synonyms Aztec TBPM-50-FT t[Aztec Peroxides] Aztec TBPM-50-P t[Aztec... 

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]... 

Exposure to styrene is the main occupational hygiene problem in reinforced plastics industry, where it is used as a crosslinking agent and solvent in unsaturated polyester resins. In addition, workers are exposed to acetone which is used as a clean-up solvent. Other solvents, such as methylene chloride, toluene, xylene, heptane (TLV 400 ppm, the Finnish OEL 300 ppm), methylcyclohexane (TLV and the Finnish OEL 400 ppm), and butyl acetate (TLV and the Finnish OEL 150 ppm) may also be used. Styrene is neurotoxic. Styrene is also a suspected carcinogen because it is metabolized via styrene-7,8-oxide. The TLV and the Finnish OEL of styrene is 20 ppm. Urinary mandelic acid concentration is the most common biological monitoring method for styrene. The ACGIH BEI is 800 mg/g creatinine and the FIOH BEI 3.2 mmol/1. 

Allyl esters, unsaturated polyesters, as well as some of what are known as vinyl or acrylic esters are cured by free radical addition polymerization. In the case of allyl esters, the monomers, themselves, are cross-linked. On the other hand, unsaturated polyesters are copolymerized with monomers such as styrene or methyl methacrylate. Since the unsaturated polyesters have many main-chain double bonds and the structure of a cross-linked network is fixed after quite low conversions, only a few double bonds actually react. These unconverted double bonds can then react later with atmospheric agents, and so produce poor weathering properties of the crosslinked networks. In addition, the polymerization produces many free chain ends that contribute nothing or even disadvantageously to the mechanical properties. The newly developed vinyl or acrylic esters avoid both of these problems in that the monomers capable of cross-linking only have unsaturated double bonds at the molecular ends (see also Section 26.4. S). 

A crosslinking agent is a reagent that promotes or regulates crosslinking. Some examples are peroxides that promote formation of crosslinks in unsaturated polyester resins and sulfur in the crosslinking (or vulcanization) of rubber. 

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