Polyester Thermoset

Thermoplastic polyesters achieved some commercial success during the mid-1980s however, these were eventually replaced by nylon coating powders in functional coatings and thermosetting polyester powders in decorative appHcations because of lack of any unique characteristics or price advantages (see Polyesters, thermoplastic). 

The thermoplastic or thermoset nature of the resin in the colorant—resin matrix is also important. For thermoplastics, the polymerisation reaction is completed, the materials are processed at or close to their melting points, and scrap may be reground and remolded, eg, polyethylene, propjiene, poly(vinyl chloride), acetal resins (qv), acryhcs, ABS, nylons, ceUulosics, and polystyrene (see Olefin polymers Vinyl polymers Acrylic ester polymers Polyamides Cellulose ESTERS Styrene polymers). In the case of thermoset resins, the chemical reaction is only partially complete when the colorants are added and is concluded when the resin is molded. The result is a nonmeltable cross-linked resin that caimot be reworked, eg, epoxy resins (qv), urea—formaldehyde, melamine—formaldehyde, phenoHcs, and thermoset polyesters (qv) (see Amino resins and plastics Phenolic resins). 

Practical methods for synthesis and elucidation of the optimum physical forms were developed at Du Pont (13). The violets fill the void in the color gamut when the inorganics are inadequate. The quinacridones may be used in most resins except polymers such as nylon-6,6, polystyrene, and ABS. They are stable up to 275°C and show excellent weatherabiUty. One use is to shade phthalocyanines to match Indanthrone Blue. In carpeting, the quinacridones are recommended for polypropylene, acrylonitrile, polyester, and nylon-6 filaments. Predispersions in plastici2ers ate used in thermoset polyesters, urethanes, and epoxy resins (14). 

Special grades of styrenic block copolymers are usehil modifiers for sheet mol ding compounds (SMC) based on thermoset polyesters. They improve surface appearance, impact resistance, and hot strength. 

Uses. There are about forty to fifty organic peroxides commercially available in more than seventy formulations designed for specific applications which include (1) initiators for vinyl monomer polymerizations, and copolymerizations of monomers such as vinyl chloride, ethylene, styrene, vinyl acetate, acrylics, fluoroolefms and buta-dienestyrene (2) curing agents for thermoset polyesters, styrenated alkyds and oils, silicone rubbers and poly allyl diglycol carbonates ... 

Thermosetting Polyester Resins 2.1.2.3.1 Unsaturated Polyester Resins... 

Thermoplastic resins, self-reinforced, 26 Thermoplastics, preparation of, 257-258 Thermoplastic step-growth polymers, 3 Thermosetting polyester resins, 29-31 Thermosetting resins, 3-4, 19 Thermotropic compounds, 49 THF. See Tetrahydrofuran (THF) Thiobisphenol S (TBPS), 364 Thionyl chloride, 80 activation of, 111 3,3 -linked polymers, 480 Tin-amine coordination complex, 234 Tin compounds, 86, 232-233... 

A plastics material of particular application in electrical components. It consists of a thermosetting polyester resin, mineral fillers, fibrous reinforcement and a hquid crosslinking medium such as diallyl phthalate. Down-Stroking Press... 

The typical resin systems include thermoset polyesters, vinyl esters, epoxies, polymi-dies, bismaleimide, and phenolics. Thermoplastics are also finding their way into filament winding. Wet thermoset filament winding requires a resin with viscosity in the range of 1000-3000 cpoise. Resin components are chosen on the basis of pot life, winding temperature, viscosity, gel time, and cure time. 

Ethylbenzene has been shown to migrate at levels of < 6-34 pg/kg Ifom samples of thermoset polyester (containing up to 25 mg/kg ethylbenzene) into pork during cooking (Gramshaw Vandenburg, 1995). 

Composite In polymer technology a combination of a polymeric matrix and a reinforcing fiber with properties that the component materials do not have. The most common matrix resins are unsaturated thermosetting polyesters and epoxies, and reinforcing fibers are glass, carbon, and aramid fibers. The reinforcing fibers may be continuous or discontinuous. Some matrix resins are thermoplastics. 

A wide variety of thermosetting polyester (alkyd) resins can be made by similar procedures. The following polybasic acids and anhydrides and poly-hydric alcohols are among the other popular ingredients in alkyd formulations ... 

Historically, PEB has been used as an additive flame retardant for thermoset polyester and thermoplastic resins during the 1970s and 1980s. In 1977, the production of PEB was 45-450 metric tons [60]. The production of PEB declined to 5-225 metric tons in 1986, and in 1988, there was no ongoing or intended production or processing of this substance [60]. Information on the current manufacturers or processors of PEB is not publicly available in addition, information on the amount of PEB currently produced (if any) is confidential. However, PEB is listed as a low-production-volume chemical manufactured by Albemarle in France according to the European... 

Thermoset resins covers an extremely wide range, including phenol formaldehyde polymers, aminopolymers, PUs, epoxies, and thermoset polyesters, which include the alkyd and unsaturated vinyl ester resins. Of special interest at the present time are those that comprise the resin component of liber-reinforced composites that are finding increasing use in commercial and defense sectors, where fire resistance is of paramount importance. Typical resins used are those listed in Table 2.4 along with typical, respective LOI values in descending order of increased inherent fire resistance. 

Gramshaw, J.W., and Vandenburg, H.J., 1995. Compositional analysis of thermoset polyester and migration of ethylbenzene and styrene from thermosct polyester into pork during cooking. Food Add. and Contam. 12, 2, 223-234. 

Injection molding can be used with some thermosets in addition to thermoplastics, as long as the process can be controlled such that the crosslinking or curing takes place in the mold and not in the extruder barrel. It has been used effectively, for example, with thermosetting polyester resins. Scrap runners or defective parts must be discarded, however, as they cannot be remelted. 

TABLE 15.20 Topical Properties of Glass-Fiber-Reinforced Thermoset Polyesters... 

Different foundry casting techniques are used. Included are plastic-based binders mixed with sand. Various types of molds and cores are produced that include no-bake or cold-box, hot-box, shell, and oven-cured. Usual binders are phenolic, furan, and thermoset polyester. There is the foundry shell casting, also called dry-mix casting. It is a type of process used in the foundry industry, in which a mixture of sand and plastic (phenolic, thermoset polyester, etc.) is placed on to a preheated metal pattern (producing half a mold) causing the plastic to flow and build a thin shell over the pattern. Liquid plastic pre-coated sand is also used. After a short cure time at high temperature, the mold is stripped from its pattern and combined with a similar half produced by the same technique. Finished mold is then ready to receive the molten metal. Blowing a liquid plastic/sand mix in a core-box also produces shell molds. 

A further difficulty with the basic materials is that they do not lend themselves readily to simple concepts and to simple comparisons. The matrix components are essentially the same plastics as those used for conventional reinforced plastic laminates. Epoxy plastics are more widely used than others, although phenolics and silicones give structures with higher temperature properties. Thermoset polyesters are used for many commercial structures in which cost is a problem and high temperatures do not prevail. 

To cite a practical example, 20% by mass of 12/mi diameter glass fibre coated with silver (70 nm thick) mixed in a thermosetting polyester resin gave a composite conductivity of 2.5 x 104fi-lm 1. From Equation (8.37) the calculated value is 5.3 x 104fl-lm-1, which compares reasonably well with the experiment, if one takes into account that some disintegration of the fibre is inevitable in the mixing process. 

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... 

Thermoset plastics have also been pyrolysed with a view to obtain chemicals for recycling into the petrochemical industry. Pyrolysis of a polyester/styrene copolymer resin composite produced a wax which consisted of 96 wt% of phthalic anhydride and an oil composed of 26 wt% styrene. The phthalic anhydride is used as a modifying agent in polyester resin manufacture and can also be used as a cross-linking agent for epoxy resins. Phthalic anhydride is a characteristic early degradation product of unsaturated thermoset polyesters derived from orf/io-phthalic acid [56, 57]. Kaminsky et al. [9] investigated the pyrolysis of polyester at 768°C in a fiuidized-bed reactor and reported 18.1 wt% conversion to benzene. 

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