Peroxide initiator polyester resin

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. 

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. 

Unsaturated polyester resins prepared by condensation polymerization constitute the largest industrial use for maleic anhydride. Typically, maleic anhydride is esterified with ethylene glycol [107-21-1] and a vinyl monomer or styrene is added along with an initiator such as a peroxide to produce a three-dimensional macromolecule with rigidity, insolubiUty, and mechanical strength. 

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. 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

Unsaturated polyester resin powders can provide a colored and finished exterior molded surface or a finish ready for painting. Normally, a primer/sealer must be appHed to molded articles prior to painting. In addition to the unsaturated polyester resin, multifimctional unsaturated monomers such as triaHyl cyanurate (TAC) [101-37-1] or diaHyl phthalate (DAP) [131-17-9] suitable peroxide initiators (qv) or mixtures thereof, and mold release agents (qv) are used to formulate the coating powder (46). 

Polyesters. Unsaturated polyester resins based on DCPD, maleic anhydride, and glycols have been manufactured for many years. At least four ways of incorporating DCPD into these resins have been described (45). The resins are mixed with a cross-linking compound, usually styrene, and final polymerization is accompHshed via a free-radical initiator such as methyl ethyl ketone peroxide. 

For a complete panel replacement, the refinisher starts with a panel preprimed in the appropriate stoving primer. For spot repairs or larger repairs without replacement of metal, there will be areas which have to be rubbed through to clean metal. Any indentations then have to be filled with a stopper or spray filler, probably based on unsaturated polyester resins and styrene, with cure initiated by mixing in an organic peroxide. After sanding, remaining bare metal areas are sprayed with a two-pack etch primer. 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

Unsaturated polyester finishes of this type do not need to be stoved to effect crosslinking, but will cure at room temperature once a suitable peroxide initiator cobalt salt activator are added. The system then has a finite pot life and needs to be applied soon after mixing. Such a system is an example of a two-pack system. That is the finish is supplied in two packages to be mixed shortly before use, with obvious limitations. However, polymerisation can also be induced by ultra violet radiation or electron beam exposure when polymerisation occurs almost instantaneously. These techniques are used widely in packaging, particularly cans, for which many other unsaturated polymers, such as unsaturated acrylic resins have been devised. 

Consist of a range of chemicals which promote cross-linking can initiate cure by catalysing ( catalysts , hardeners, initiators), speed up and control cure (activators, promoters) or perform the opposite function (inhibitors) producing thermosetting compounds and specialised thermoplastics (e.g. peroxides in polyesters, or amines in epoxy formulations). The right choice of a cure system is dependent on process, process temperature, application and type of resin. 

The free-radical cure mechanism of the vinyl ester resins is well understood. In most respects, it is similar to that of the unsaturated polyester resins. To initiate the curing process, it is necessary to generate free radicals within Ike resm mass. Organic peroxides are tlie most common source of free radicals. These peroxides will decompose under the influence of elevated temperatures or chemical promoters, e.g., organometallics or tertiary amines, to form free radicals. Generation of free radicals also can be effected by ultraviolet or high-energy radiation applied directly to the resin system. The free radicals thus formed react to open the double bond... 

Polyethylene and a peroxide initiator were added to the usual BPA/DC-BMI-epoxide resin composition. The use of unsaturated polyesters from tetrabromo-phthalic anhydride, maleic anhydride and ethylene glycol as well as of other fire retardants was also described [99]. 

Aryl-substituted enolizable keto compounds initiate the copolymerization of unsaturated polyesters with styrene. Gel times of the same order as those obtained with conventional peroxide initiators can be attained exotherms, however, are considerably lower, this latter effect being of technological interest—e.g., casting resins. Since a radical mechanism has been proved, it is postulated that radicals result from keto hydroperoxides which have been formed from the aryl-substituted enols via autoxidation. Steric effects and resonance may partly account for differences in the catalytic activity of some and for the inhibiting effect of other ketones and enols. NMR spectroscopy indicates further that cis-trans isomerism may influence the catalytic effectiveness of pure enols. 

A general purpose (i.e., conventional) unsaturated polyester resin (Aropol 7030, Ashland Chemical Company) and a vinyl ester resin (XD-7608.05, Dow Chemical Company) were used for the study. Benzoyl peroxide in granular form (Cadox BPP-60 WET, Noury Chemical Corp.) was used as initiator, and a solution of 5 wt. % N,N-dimethylaniline (Aldrich Chemical Company) diluted in styrene was used as promoter. 

T. Urbahski and Bu niak [140, 141] undertook the task of a systematic study of the action of mono-, di- and trinitro derivatives of benzene and toluene (a few dozen compounds) on the polymerization of unsaturatcd polyester resin Polymal 109. The polymerization was initiated with benzoil peroxide at 12°C. 

Aztec . [Catalyst I ources] Peroxide deiivs. crosdinking agoit catalyst in polyethylene crosslinl g, styrene polymerization, polyester resins vulcanizing agent for SB NBR, EPDM, EPM, silicones initiate in polymer-izadort... 

Cadet . [Akzo] Benzoyl peroxide initiator ftH curing unsat polyester resins. 

Cadox . [Akzo] Organic peroxide compds. initiator to curing polyester resins crosslinking agent to curing silicone rubbers. 

Decanox-F. [AtochemN. Am.] Decanoyl peroxide initiator for polymerization, curing elastomers and polyester resins. 

Esperfoam . [Witco/Argus] Peroxide derivs. initiator for polymerization of ethylene, styrene, acrylates, curing of unsat. polyester resins crosslinking agent for chlorinated polyethylene. 

Laurox . [Akzo] Peroxides initiator for prod, of PVC resins, acrylates, high temp, polyester cures. 

Luperox. [Atochem N. Am.] Organic peroxide compds. initiator for poly-meiizaticHi, polymer modification, dier-moplastic crosslinking, curing elastomers, high-tenq>. cure ci polyester resins. 

Dimethylethyl 1-methyl-1-phenylethyl peroxide, tert-Butyl a,a-dimethylbenzyl peroxide EINECS 222-389-8 Luperco 801-XL Peroxide, 1,1-dimethylethyl 1-methyl-1-phenylethyl Trigonox T. Used as an initiator for high-temperature cure of polyester resins, curing elastomers, and polymer modification thermoplastic cross-linking. ElfAtnchem N. Am. 

Laurox Lauroyl peroxide Laurydoi LYP 97 LYP 97F NSC 670 Peroxide, bis(l-oxododecyl)- Peroxide, didodecanoyl Peroxyde de lauroyle. Initiator for bulk, solution, and suspension polymerization, high-temperature curing of polyester resins, and cure of acrylic syrup. White plates mp = 49 insoluble in H2O, soluble in CHCI3. Elf Atochem N. Am. 

Aztec . [C yst Resources] Peroxide derivs. ciosslinking agent, catalyst in polyethylene ctosslinking, styrene po-lymeiizatkm, polyester resins vulcanizing i ent to SB NBR, EPDM, EI silicones initiator in polymerization. 

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