Thermoplastic polyester composite properties

Table 15.2 Selected properties of 30% glass-fiber-reinforced (GFR) thermoplastic polyester composites [15-17]...

Polyesters are known to be produced by many bacteria as intracellular reserve materials for use as a food source during periods of environmental stress. They have received a great deal of attention since the 1970s because they are biodegradable, can be processed as plastic materials, are produced from renewable resources, and can be produced by many bacteria in a range of compositions. The thermoplastic polymers have properties that vary from soft elastomers to rigid brittie plastics in accordance with the stmcture of the pendent side-chain of the polyester. The general stmcture of this class of compounds is shown by (3), where R = CH3, n = >100, and m = 0-8. 

Polyester polyols, 25 464 468 Polyester resin(s), 11 302 coating resins, 7 104-106 cyclopentadiene and dicyclopentadiene applications, 8 230 flammability of, 20 115-116 properties in powder coating, 7 43t standard test methods for, 20 11 It unreinforced, 10 187t weathering of, 20 116 Polyester resin-based powder coatings, organic titanium compounds in, 25 125 Polyester resin composites, 26 762-763 Polyester resin formulations ingredients of, 20 96t unsaturated, 15 511-512 Polyesters, 10 185-189, 497 12 655-656. See also Thermoplastic polyesters Unsaturated polyesters acid resistance of, 20 7-8 antioxidant applications, 3 121 aromatic ionic, 23 722 based on 1,4-cyclohexanedimethanol, 12 674-675... 

The surface energy of fibers is closely related to the hydrophilicity of the fiber [6]. Some investigations are concerned with methods to decrease the hydrophilicity. The modification of wood-cellulose fibers with stearic acid [10] hydrophobizes those fibers and improves their dispersion in polypropylene. As can be observed in jute reinforced polyester composites, treatment with polyvinylacetate increases the mechanical properties [10] and moisture repel-lence [60]. Several similar investigations on biobased composites based on thermoplastic and thermoset matrices have been reported by several authors [61-63]. Some of the major findings based on the authors own experimental investigations are discussed in the following sections. 

Reinforced plastics are composites in which a resin is combined with a reinforcing agent to improve one or more properties of the resin matrix. The resin may be either thermosetting or thermoplastic. Typical thermosetting resins used in RPs include unsaturated polyester, epoxy, phenolic, melamine, silicone, alkyd, and diallyl phthalate. In the field of reinforced thermoplastics (RTFs), virtually every type of thermoplastic material can be, and has been, reinforced and commercially molded. The more popular grades include nylon, polystyrene, polycarbonate, polyporpylene, polyethylene, acetal, PVC, ABS, styrene-acrylonitrile, polysulfone, polyphenylene sulfide, and thermoplastic polyesters. 

Yet another limitation associated with the use of lignocellulosic fillers is the fact that the processing temperature of composites must be restricted to just above 200°C (although higher temperatures can be used for short periods of time), because of their susceptibility to degradation and/or the possibility of volatile emissions that could affect the composite properties. This limits the types of thermoplastics that can be used to polymers like polyethylene, PP, poly-vinyl chloride and polystyrene, which constitute, however, about 70 per cent of all industrial thermoplastics. Nevertheless, technical thermoplastics like polyamides, polyesters and polycarbonates, which are usually processed at temperatures higher than 250°C, cannot be envisaged as matrices for these types of conposite. 

About 10 years ago Wiley-VCH published in two volumes (totally 1400 pages) the Handbook of Thermoplastic Polyesters, which covered the synthesis, structure and properties, blends and composites of the commercially available to that time thermoplastic polyesters, as well as their recycling opportunities. But, practically, nothing about the biodegradable polyesters has been mentioned in this book. 

Several recent patents concern thermoplastic polyesters for electrical goods. DuPont has disclosed a moulding composition for PBT, to which is added a reinforcement and a mixture of melamine pyrophosphate with an aromatic phosphate oligomer. The physical properties are reported to be good (EP 903370). 

Fakirov S, Evstatiev M and Friedrich K (2000) Nanostructured polymer composites from polyester blends Structure-properties relationship, in Handbook of thermoplastic polyesters (Ed. Fakirov S) Wiley-VCH, Weinheim, Germany, pp. 1093-1129. 

S. Fakirov, M. Evstatiev and K. Friedrich, Nanostructured polymer composites from polymer blends morphology and mechanical properties, in Handbook of Thermoplastic Polyesters Homopolymers, Copolymers, Blends, and Composites (ed. S. Fakirov), Wiley-VCH Verlag GmbH, Weinheim, Germany, Ch. 23, pp. 1093-1132, 2002. 

Automotive and electrical/electronics industries are the largest markets for engineering polymers which include Crastin PBT polyesters, Hytrel thermoplastic polyester elastomers, Rynite PET, high-temperature Thermx PCT (polycyclohexylene dimethyl terephthalate), Tribon composites and Tynex filaments, Vespel polyimide parts and shapes, Zenite liquid crystal polymers and Zytel PA resins. In July 2005, DuPont launched the DuPont Vespel SP-202 composition whose properties include the prevention of static charge build-up. Other products include Delrin acetal resins, engineering thermoplastic vulcanisates. Minion mineral reinforced PA resins and Teflon PTFE fluoropolymer resins. 

T. F. Gray, Jr., Properties of a New Glass-Fiber Reinforced Thermoplastic Polyester , 26tA Annual Technical Conference, Reinforced Plastics/Composites Division, Society of the Plastics Industry, Inc., Washington, DC, 1971. 

---