[strella6black]

PET is the most widely used polyester. It finds major uses in the textile and packaging industries. PET Fibers (Mylar, Dacron, and Terylene) have excellent crease and wear resistance and low moisture absorption, and cloth made from PET exhibts good wrinkle resistance. As a thermoplastic, PET is mainly used for the production of films (BOPET) and blow-molded bottles for carbonated soft drinks. Other uses of (filled) PET include handles and housings for appliances (cookers, toasters, shower heads, industrial pump housings etc.) In engineering applications, PET is often reinforced with glass fibers or compounded with silicates, graphite and other fillers to improve strength and rigidity. The glass reinforced grades are rated for continuous use temperatures up to 410 - 430 K. here

[dtvan]

Major manufacturers of unfilled and filled semi-aromatic polyesters are SABIC, DuPont, Invista, BASF and Celanese. The most important resins are PET and PBT. A large number of commercial grades are available. Many are reinforced with up to 50 percent glass. Other important semi-aromatic polesters are polytrimethylene terephthalate (PTT) and polyethylene naphthalate (PEN).
Major manufacturers of aromatic polyesters are Kuraray ( Vectran ® ), Celanese ( Vectra ® ), and DuPont ( Zenite LCP ® ). here

[andyc]

Another important polyester is polyethylene naphthalate (PEN). Compared with PET, it has lower oxygen permeability, improved hydrolytic stability, higher tensile strength and service temperature, and reduced elongation and shrinkage due to the higher Tg (120°C vs 75°C). PEN usually surpasses PET in top end demanding applications and is often a good and less expensive alternative to polyimides.

[jstn]

Fully aromatic polyesters are produced on a very small scale. They are rather expensive and find some applications in the aerospace industry, as well as in some other industries as high performance arylate fibers for very demanding applications. Their performance competes with that of aramide fibers. Some applications include cut resistant gloves, chain saw chaps, high pressure inflatables, abrasion-resistant fabrics, and chemically resistant gaskets.

[jtimon]

Polyesters are one of the most important classes of thermoplastic polymers. They can be formed from the reaction of a diacid or acid anhydride and a diol with the elimination of water, or by ring-opening polymerization of cyclic (di-)esters. According to the composition of their main chain, polyesters are classified as aliphatic, semi-aromatic and aromatic (see table below). Aromatic reactants improve the hardness, rigidity, and heat resistance, whereas aliphatic acids and diols increase the flexibility, lower the melting or softening point and improve the processability.
Common aliphatic diols are ethylene glycol, 1,4-butanediol, and 1,3-propanediol. They are often reacted with aromatic diacids, such as terephthalic acid, phthalic acid, phthalic anhydride and naphthalene dicarboxylic acid. Glycerol and unsaturated acids (anhydrides) like maleic anhydride, are sometimes added to crosslink the polyesters. In the case of unsaturated acids (anhydrides), crosslinking is achieved in a subsequent free radical chain polymerization. Double bonds in the backbone of the polyesters also improve the resistance to softening and deformation at elevated temperatures.

[Vasili Sviridov]

Roy J. Crawford , James L. Throne , in Rotational Molding Technology , 2002

[throughput]

Low exothermic heat is used for thick laminates to minimize the heat given off during cure, an important consideration for parts with extremely thick sections. more

[w8ks6]

Unsaturated polyester resin (UPE) * was one of the earliest liquid polymers to be rotationally molded. 22 ** Like PVC, polyester is a 19th century polymer. In 1847, Berzelius reacted tartaric acid with glycerol to produce a sticky resin. Lorenzo reacted ethylene glycol with succinic acid in 1863 to produce a second polyester. Today, polyester is prepared by reacting diethylene glycol, HO–CH₂–CH₂–OH, and an unsaturated aliphatic acid such as maleic acid, HOOC–CH=CH–COOH. The still-unsaturated polyester resin is then dissolved in an unsaturated, reactive solvent such as styrene or α-methyl styrene. The resin viscosity is adjusted by the extent of polymerization of the polyester, the nature of the ingredients used to produce the polyester, and by the amount of reactive solvent. The resin is crosslinked by adding a free-radical catalyst such as methyl ethyl ketone peroxide (MEKP). Polyester resin reactions are typically very slow, with gelation taking many minutes. The reaction exotherm is developed mainly after the polyester resin has gelled into an intractable structure. Polyester resins have great affinity for fillers and reinforcements, with filler loading as high as 70% (wt) possible. Fillers include calcium carbonate and talc inorganics and wood flour organics. Reinforcements include cotton lintels and fiberglass. Furthermore, polyester resins can be painted and stained, and have excellent weather resistance. As a result, thermosetting polyester resins have found extensive use in furniture and construction. In rotational molding, the polyester resins must be heated to initiate reaction in reasonable times. As discussed below, care must be taken to ensure that the resin fully coats the mold surface prior to gelation. Otherwise the gelling resin remaining in the pool will wipe the resin from the mold surface. The difficulty in balancing the heating and reaction aspects of rotationally molding catalyzed unsaturated polyester resin has limited its applications despite its exceptional price/performance ratio.

[Netsniper]

* Impact at cold temperatures is likely to cause strand cracking or breakage

[Stobrawa]

* Made from resin that is not compliant with FDA regulations for food contact, unless otherwise specified (product number dependent / specific). more

[UndeadCircus]

* Polypropylene products produced for some filtration applications are made from resin that complies with FDA regulations for food contact. The regulation compliance is product number dependent / specific.

[srf21c]

The effects of comonomer composition on the curing kinetics of unsaturated polyester (UP) resins at 40°C were studied by differential scanning calorimetry (DSC) and infrared spectroscopy (IR) over the entire conversion range. Two commercial UP resins, including UP2821 and UP536B, which on the average contained 6.82 and 4.16 unsaturated CC bonds per polyester molecule, respectively, by 1 H-NMR analysis, were used. Experimental results showed that for UP536B reactions initiated by BPO (benzoyl peroxide)/DMA (N,N-dimethyl aniline) amine accelerated system, at higher molar ratio of styrene to polyester CC bonds, the DSC rate profile at 40°C exhibited a shoulder after the peak, which could be caused by the grafting reaction of styrene on CC bonds of the polyester chain inside the microgel particles. In contrast, for UP2821 resin, no shoulder was observed presumably because UP2821 reaction systems would lead to a higher crosslinking density during the cure, and styrene molecule could not readily diffuse into the microgel structure at the later stage of the reaction for the reaction shoulder to appear. A microgel-based reaction mechanism was thus proposed due to the experimental results. © 1992 John Wiley & Sons, Inc. more

[robmon]

[alkor]

[JasonStarr]

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