Polyester resins cross-linking

Alkyds are formulated from polyester resins, cross-linking monomers, and fillers of mineral or glass. The unsaturated polyester resins used for thermosetting alkyds are the reaction products of polyfunctional organic alcohols (glycols) and dibasic organic acids. 

Poly(methyl methacrylate) and poly(vinyl acetate) precipitate from the resin solution as it cures. This mechanism offsets the contraction in volume as the polyester resin cross-links, resulting in a nonshrinking thermoset. Other polymer additives such as poly(butylene adipate) provide similar shrinkage... 

Structures present in cured polyester resin. Cross-linking via an addition copolymerisation reaction. The value of n 2-3 on average in general purpose resins... 

Thermoset polyester Polyester resins cross-linked with amino or phenolic resins May contain lower molecular weight epoxy resin Very good Pack dependent May not be suitable for very acidic and aggressive foods... 

Sloane, Boerio and Koenig, and McGraw have described the sampling and other instrumental considerations for Raman spectra of polymers (144). Other reports on Raman investigations of polymers include molecular orientation in bulk polyethylene terephthalate (145). crystallinity of ethylene-propylene rubber (146). and the structure of unsaturated polyester resins cross-linked with styrene (147). 

Indirect food additive—polyester resins, cross-linked solvents for inhibitors, accelerators, and catalysts... 

FDA. 2000e. Polyester resins, cross-linked. National Archives and Records Administration. Code of Federal Regulations. 21 CFR 177.2420, Appendix B. 

FIGURE 4.12 Curing of unsaturated polyesters, (a) Species in polyester resin ready for laminating, (b) Structures present in cured polyester resin. Cross-linking takes place via an addition copolymerization reaction. The value of n 2-3 on average in general-purpose resins. (After Brydson, J. A. 1982. Plastics Materials. Butterworth Scientific, London, UK.)... 

High molecular mass polyester resins, cross-linked with benzoguanamine and melamine resins, are particularly suitable for highly drawable. sterilization-resistant decorative stamping enamels [2.88], [2.89]. Low molecular mass polyester resins also exhibit good processability and sterilization resistance in polyurethane formulations. 

Surfacers are mainly produced from low molecular mass polyester resins cross-linked with amino resins. Blocked polyisocyanate resins may also be used for high stone chip resistance. Water-soluble polyester resins are increasingly used for water-thinnable stoving surfacers. Spray and dip paints based on polyester resins are used to coat automobile accessories (e.g., windscreen wipers, axle parts). 

Polyester resins, cross-linked butyl ben l phthalate (containing not more than 1.0 wt% of dibenzyl phthalate), dibutyl ph alate, dimethyl phdialate, triphenyl phosphate... 

Alkyds. Alkyd resins (qv) are polyesters formed by the reaction of polybasic acids, unsaturated fatty acids, and polyhydric alcohols (see Alcohols, POLYHYDRic). Modified alkyds are made when epoxy, sUicone, urethane, or vinyl resins take part in this reaction. The resins cross-link by reaction with oxygen in the air, and carboxylate salts of cobalt, chromium, manganese, zinc, or zirconium are included in the formulation to catalyze drying. 

The traditional cross-linking technologies utilized in the coatings market range from hydroxyl functional binders (acrylics or polyesters) cross-linked with melamines (IK) or isocyanates (2K) to drying oils that cure through oxidation of unsaturation in the backbone, to epoxy resins cross-linked with amino resins (amido amines, amines, etc.). 

One major use of polyesters, the alkyd coating resins, is based on random prepolymers reacted with unsaturated fatty acids. Gelation phenomena have been studied extensively and the gelation theories of Carothers, Flory, and Stock-mayer were developed with polyester random prepolymers. Only recently, Gordon (iJ, 12) has extended the gelation theory to the structopendant polyester system cross-linked by vinyl monomers. 

Vibrin [Uniroyal], TM for resin compositions of polyesters and cross-linking monomers that when catalyzed, will polymerize to infusible solid resins without evolving water or other by-products. 

Solvents used for paint removal are able to dissolve or considerably swell physically drying binders (e.g., vinyl chloride copolymers, cellulose nitrate, polyacrylates) and chemically cross-linked coatings (e.g., oil-based paints, dried alkyd resins, cross-linked polyester-melamine resins, cross-linked epoxy and isocyanate coatings) [14.237]. A combination of dichloromethane with low-boiling ketones or esters is particularly suitable. Small amounts of high-boiling solvents with a low volatility (e.g., tetrahydronaphthalene, solvent naphtha, methyl benzyl alcohol, or benzyl alcohol) are added to these mixtures to retard evaporation and increase the solvency. Modern paint removers do not contain chlorinated hydrocarbons, they are formulated on the basis of high boilers (e.g., dimethylformamide, dimethyl sulfoxide, propylene carbonate, and yV-methylpyrrolidone) in combination with alcohols and aromatics, or consist of aqueous, frequently alkaline or acidic systems. 

It can be concluded that the beverage can coating is a methyl melhacrylate/eth-ylhexyl acrylate copolymer modified polyester. The polyester is an adipic acid-modified neopentyl glycol iso-/orthophthalic acid type. The electrical appliance coating is a butylated amino resin cross-linked pentaerythritol-orlhophthalic thermosetting alkyd enamel. 

The most common resins used are vinyls, chlorinated rubber, acrylics, epoxies, urethanes, polyester, autooxidative cross-linking coatings, and water soluble 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. 

The commonly used resins in the manufacture of decorative and industrial laminates ate thermosetting materials. Thermosets ate polymers that form cross-linked networks during processing. These three-dimensional molecules ate of essentially infinite size. Theoretically, the entire cured piece could be one giant molecule. The types of thermosets commonly used in laminates ate phenoHcs, amino resins (melamines), polyesters, and epoxies. 

Polymers. AH nitro alcohols are sources of formaldehyde for cross-linking in polymers of urea, melamine, phenols, resorcinol, etc (see Amino RESINS AND PLASTICS). Nitrodiols and 2-hydroxymethyl-2-nitro-l,3-propanediol can be used as polyols to form polyester or polyurethane products (see Polyesters Urethane polymers). 2-Methyl-2-nitro-l-propanol is used in tires to promote the adhesion of mbber to tire cord (qv). Nitro alcohols are used as hardening agents in photographic processes, and 2-hydroxymethyl-2-nitro-l,3-propanediol is a cross-linking agent for starch adhesives, polyamides, urea resins, or wool, and in tanning operations (17—25). Wrinkle-resistant fabric with reduced free formaldehyde content is obtained by treatment with... 

Organic peroxides are used in the polymer industry as thermal sources of free radicals. They are used primarily to initiate the polymerisation and copolymerisation of vinyl and diene monomers, eg, ethylene, vinyl chloride, styrene, acryUc acid and esters, methacrylic acid and esters, vinyl acetate, acrylonitrile, and butadiene (see Initiators). They ate also used to cute or cross-link resins, eg, unsaturated polyester—styrene blends, thermoplastics such as polyethylene, elastomers such as ethylene—propylene copolymers and terpolymers and ethylene—vinyl acetate copolymer, and mbbets such as siUcone mbbet and styrene-butadiene mbbet. 

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