Polyester, aliphatic thermoplastic

Phthalazinone, 355 synthesis of, 356 Phthalic anhydride, 101 Phthalic anhydride-glycerol reaction, 19 Physical properties. See also Barrier properties Dielectric properties Mechanical properties Molecular weight Optical properties Structure-property relationships Thermal properties of aliphatic polyesters, 40-44 of aromatic-aliphatic polyesters, 44-47 of aromatic polyesters, 47-53 of aromatic polymers, 273-274 of epoxy-phenol networks, 413-416 molecular weight and, 3 of PBT, PEN, and PTT, 44-46 of polyester-ether thermoplastic elastomers, 54 of polyesters, 32-60 of polyimides, 273-287 of polymers, 3... 

Polyesters A broad class of polymers usually made by condensation of a diol with dicarboxylic acid or anhydride. Polyesters consist of chains with repeating carbonyloxy group and can be aliphatic or aromatic. There are thermosetting polyesters, such as alkyd resins and unsaturated polyesters, and thermoplastic polyesters such as PET. The properties, processing methods, and applications of polyesters vary widely. Also called Polyester Resins. 

Chem. Descrip. Sat., aliphatic, linear, hydroxyl-terminated polyester diol Uses Polyester for thermoplastic elastomers, laminating adhesives, hot melt and sol n. coatings, and one-shot and prepolymer castables Features PUs exhibit hydrolysis resistance, heat aging and weathering, strong, resilient elastomers, thermoplastic processability, and low temp, properties melts at mod. temps. 

Uses Lt. stabilizer for PP, ABS, PS, nylon, LDPE, LLDPE, HOPE, acrylics, PC, thermoplastic polyester, SAN, thermoplastic elastomers, surf, coatings, suitable for thin films, fibers, or molded parts Features Esp. effective in polyolefins for outstanding heat and processing stability use with UV-Chek AM-340 Properties Lt. amber micro-pastille very sol. in aromatic hydrocarbons, ketones, esters, some alcohols very low sol. in aliphatic hydrocarbons and water misc. with methylene, methylene chloride m.w. > 2400 sp.gr. 1.03 bulk dens. 5.8 Ib/gal soften, pt. 100 C min. 

Aliphatic thermoplastic polyesters represent a class of materials that is attracting a considerable amount of attention because they are i) biodegradable and biocompatible and ii) increasingly accessible from the exploitation of diols and dicarboxylic acids derived from renewable resources. If long methylene chains are present in the monomers, the ensuing products resemble polyethylene (PE) in strnctnre and, hence, in most properties, have the added advantage of biodegradability. 

The molecular structure of polylactic acid (PLA) is schematically presented in Fig. 2.2. PLA, linear aliphatic thermoplastic polyester, is prepared from lactic acid. Lactic acid (2-hydroxy propionic acid) is one of the simplest chiral molecitles and exists as two stereo isomers, L- and D-lactic acid (Fig. 2.3). 

Lactic acid is a linear, aliphatic thermoplastic polyester with a rigidity and clarity similar to polystyrene and poly(ethylene terephthalate) (PET Martin and Averous, 2001). It is a hydroxycarboxylic acid having a chiral center on its second carbon. Because of the presence of fxmctional groups in a 3-carbon molecule, a lot of chemical reactivity can be incorporated. The carboxylic acid group is mildly acidic, and the stereochemistry of the second carbon is very important in the PLA chemistry (Garlotta, 2001 Gupta and Kumar, 2007). The major characteristics of lactic acid are presented in Table 14.2. Lactic acid comprises two optical isomers of lactic acid L (+)-lactic acid and D(-)-lactic acid. 

For an aliphatic polyester, poly(pivalolactone) has a rather high of 245°C and for such a an unexpectedly low of -10°C. It is also claimed to have good hydrolysis resistance for a polyester and this appears to be one of the reasons for its manufacture on an experimental scale by Shell with a view for use as both a fibre and as a thermoplastics moulding material. 

Polycarbonates. Linear thermoplastic polyesters of carbonic acid with aliphatic or aromatic di-hvdroxv compds. A general structure presentation is as follows (Ref 4) ... 

Aromatic-aliphatic polyesters, in which either R1 or R2 is aromatic, are generally high-melting (150-270°C) semicrystalline materials that find applications as engineering thermoplastics, films, or fibers. 

This class of polyesters consists of four major commercial polymers and their copolymers, namely PET, PTT, PBT, and PEN (see Table 2.1). They compete for engineering thermoplastics, films, and fibers markets with other semicrystalline polymers, such as aliphatic polyamides, and for some other applications with amorphous engineering plastics such as polycarbonate. The syntheses of PET and PBT, detailed in numerous reviews and books,2-5 are described in Sections 23.2.2 and 2.3.2.1. 

PET, PTT, and PBT have similar molecular structure and general properties and find similar applications as engineering thermoplastic polymers in fibers, films, and solid-state molding resins. PEN is significantly superior in terms of thermal and mechanical resistance and barrier properties. The thermal properties of aromatic-aliphatic polyesters are summarized in Table 2.6 and are discussed above (Section 2.2.1.1). 

Aliphatic polyesters occupy a key position in the field of polymer science because they exhibit the remarkable properties of biodegradability and biocompatibihty, which opens up a wide range of applications as environmentally friendly thermoplastics and biomaterials. Three different mechanisms of polymerization can be implemented to synthesize aliphatic polyesters (1) the ring-opening polymerization (ROP) of cyclic ketene acetals, (2) the step-growth polymerization of lactones, and (3) the ROP of lactones (Fig. 1). 

Another interesting example of lactones are the p-hydroxyalkanoates, whose ROP affords poly(p-hydroxyalkanoate)s (PHAs), a class of aliphatic polyesters naturally produced by bacteria (Fig. 3) [12, 13]. Poly(3-(R)-hydroxybutyrate) (PHB) is a typical example. PHB is a stiff thermoplastic material with relatively poor impact strength, but the incorporation of other monomers can improve the mechanical properties. 

Crystalline polymers exhibit the following basic properties They are opaque as long as the size of the crystallites or spherulites, respectively, lies above the wavelength of light. Their solubility is restricted to few organic solvents at elevated temperature. The following crystalline polymers have attained technical importance as thermoplastic materials polyethylene, polypropylene, aliphatic polyamides, aliphatic/aromatic polyamides, aliphatic/aromatic polyesters, poly-oxymethylene, polytetrafluoroethylene, poly(phenylene sulfide), poly(arylene ether ketone)s. 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aliphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly (glyc olide), or poly (lac tide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on p oly (butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottle resin. 

Thermoplastic copolyester elastomers are generally block copolymers produced from short-chain aliphatic diols, aromatic diacids, and polyalkylene ether-diols. They are often called polyesterether or polyester elastomers. The most significant commercial product is the copolymer from butane-1,4-diol, dimethyl terephthalate, and polytetramethylene ether glycol [25190-06-1/, which produces a segmented block copolyesterether with the following structure. 

Among the polyurethane, polyester, and polyamide thermoplastic elastomers, those with polyether-based elastomer segments have better hydrolytic stability and low temperature flexibility, whereas polyester-based analogues are tougher and have the best oil resistance (43). Polycaprolactones and aliphatic polycarbonates, two special types of polyesters, are used to produce premium-grade polyurethanes (12). 

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