Unsaturated polyester resins polymerization

Initiation of unsaturated polyester resin polymerization by electron beam, r radiation,and UV... 

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. 

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. 

Styrene [100-42-5] (phenylethene, viaylben2ene, phenylethylene, styrol, cinnamene), CgH5CH=CH2, is the simplest and by far the most important member of a series of aromatic monomers. Also known commercially as styrene monomer (SM), styrene is produced in large quantities for polymerization. It is a versatile monomer extensively used for the manufacture of plastics, including crystalline polystyrene, mbber-modifted impact polystyrene, expandable polystyrene, acrylonitrile—butadiene—styrene copolymer (ABS), styrene—acrylonitrile resins (SAN), styrene—butadiene latex, styrene—butadiene mbber (qv) (SBR), and unsaturated polyester resins (see Acrylonithile polya rs Styrene plastics). 

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. 

Maleic anhydride is important as a chemical hecause it polymerizes with other monomers while retaining the double bond, as in unsaturated polyester resins. These resins, which represent the largest end use of maleic anhydride, are employed primarily in fiber-reinforced plastics for the construction, marine, and transportation industries. Maleic anhydride can also modify drying oils such as linseed and sunflower. 

An unsaturated polyester resin consists of a linear polyester whose chain contains double bonds and an unsaturated monomer such as styrene that copolymerizes with the polyester to provide a cross-linked product. The most common unsaturated polyester is made by step growth polymerization of propylene glycol with phthalic and maleic anhydrides. Subsequent treatment with styrene and a peroxide catalyst leads to a solid, infusible thermoset. 

Parker, E. E. and J. R. Peffer, Unsaturated Polyester Resins, Chap. 3 in Polymerization Processes, C. E. Schildknecht, ed. (with I. Skeist), Wiley-Interscience, New York, 1977. 

In the manufacture of unsaturated polyester resins the polyester is synthesized and then diluted with a vinyl reactive monomer such as styrene (see POLYESTERS, UNSATURATED). A portion of the dibasic acid of the polyester is maleic or some other vinyl reactive diacid that can be polymerized with the styrene to yield a highly cross-linked, high performance polymer system. Other esters made with propylene glycol, dipropylene glycol, and tripropylene glycol are used as emulsifiers in foods, as plasticizers in polymer systems, and as part of acrylate resin systems. 

Dialkylperoxides are used as high temperature catalysts for suspension and bulk polymerization as well as hardeners for unsaturated polyester resins and for cross-linking polymers because of their good thermal stability. While the liquid di-tert-butylperoxide is relatively volatile at application temperatures, dicumylperoxide is much less volatile and has the disadvantage of forming decomposition products with intense odors (acetophenone)(Chapter 13). 

Fig. 12-. Schematic representation of the produclion of an unsaturated polyester resin and subsequent cross-linking by polymerizing the styrene in a mixture of this monomer with the polyester.

The efficiencies of benzoin derivatives in promoting the light induced hardening of styrene-containing unsaturated polyester resins have been found to vary considerably (7), benzoin alkyl ethers and a-alkylated benzoins being more reactive than benzoin itself. However, as photoinitiators for the polymerization of bulk methyl methacrylate, benzoin and benzoin methyl ether exhibit comparable efficiencies (20), and this is also indicated for polymerisation of methyl acrylate in tert-butanol (21). The relative photoinitiating efficiencies of benzoin derivatives may be influenced by several factors, some of which will depend on the nature of the monomer system and the environment in which the polymerizations are carried out. 

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. 

The materials employed for making hollow microspheres include inorganic materials such as glass and silica, and polymeric materials such as epoxy resin, unsaturated polyester resin, silicone resin, phenolics, polyvinyl alcohol, polyvinyl chloride, polyjM-opylene and polystyrene, among others, commercial jx oducts available are glass, silica, phenolics, epoxy resin, silicones, etc. Table 36 shows low-density hollow spheres. Table 37 shows physical properties of glass microspheres, and Table 38 shows comparison of some fillers on the physical properties of resulting foams (10). 

Use Catalyst for vinyl polymerizations and for curing unsaturated polyester resins, blowing agent for plastics. 

The greatest use of MAN is in the formation of unsaturated polyester resins. The polymeric resin is formed from the reaction between MAN, ethylene glycol, and a vinyl monomer. The production of MAN is carried out in most of the existing processes by a selective oxidation of n-butane over a vanadium-phosphorus oxide (VPO) catalyst. The main selective and nonselective reactions that occur are... 

Similar plots can be obtained from kinetic data of unsaturated polyester resins (24, 25). This behavior is independent of the identity of the nitrogen substituents of the amine or the monomer. Previous publications from this laboratory have pointed out that the a+ value of the amine ring substituent yielding maximum reactivity, i.e., minimum polymerization (or cure) time, occurs at approximately -0.2 in the cases examined (26-29). The optimum value is anticipated to be fairly insensitive to the type of monomer and experimental conditions. 

Figure 4. Effect of dose rate on polymerization temperature of Norsodyne styrene-unsaturated polyester resin.

Polymeric compounds are specific sealing materials intended to line or impregnate conducting hardware as well as electric radio circuits for electric insulation. They are based on epoxy and unsaturated polyester resins, liquid organosilicon rubbers and monomers (initial products for S3mthesizing pol3Tnethacrylates and polyurethanes). Compounds based on thermoplastic materials (tar, rosin, cerezin) in the form of solid or wax-like masses, heated for transformation into the liquid state, are confined to this application. 

Between 1930 and the onset of World War II (WWII) in 1939, several polymer families were invented and commercially developed through bulk processes. The most important ones include low density polyethylene (LDPE), poly(methyl methacrylate) (PMMA), polyurethanes (PU), poly(tetra-fluoro ethylene) (PTFE), polyamides (PAs), and polyesters (PEs). The last three are attributed to Dupont s scientists Roy Plunkett and Wallace Carothers, respectively. During WWll, bulk polymerization was still instrumental in the development and commercialization of new families of PEs such as polyethylene terephthalate (PET) developed by ICI and Dupont and unsaturated polyester resins (UPRs) [1, 6-8]. 

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