Polyethylene terephthalate thermal properties

K. Stoeffler, P. G. Lafleur, and J. Denault, Thermal decomposition of various alkyl onium organoclays Effect on polyethylene terephthalate nanocomposites properties. Polymer Degradation and Stability, 93 (2008), 1332-50. 

All of these intermolecular forces influence several properties of polymers. Dispersion forces contribute to the factors that result in increased viscosity as molecular weight increases. Crystalline domains arise in polyethylene because of dispersion forces. As you will learn later in the text, there are other things that influence both viscosity and crystallization, but intermolecular forces play an important role. In polar polymers, such as polymethylmethacrylate, polyethylene terephthalate and nylon 6, the presence of the polar groups influences crystallization. The polar groups increase the intensity of the interactions, thereby increasing the rate at which crystalline domains form and their thermal stability. Polar interactions increase the viscosity of such polymers compared to polymers of similar length and molecular weight that exhibit low levels of interaction. 

Tedlar is moderate in cost and has known long-term performance out-of-doors. It has excellent toughness, good weather resistance, and moderately good electrical and optical performance. Its thermal stress resistance is marginal but adequate (2-6> shrinkage at 150°C) for most needs. Its cost is higher than optimum, but can be used as a thin film, especially when coupled with less expensive polyethylene terephthalate film for better electrical properties at a lower cost. 

K.A. Tawab, S.M. Ibrahim, M.M. Magida, The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA). J. Radioanal. Nucl. Chem. 295, 1313-1319 (2013)... 

Polyethylene PET is a thennoplastic polyester made by condensing ethylene glycol terephthalate (PET) and terephthalic acid. PET is stable in a wide range of chemicals and possesses good mechanical, electrical, and thermal properties. It has one of tlie highest densities of the six primary thermoplastics. 

The thermal and mechanical properties of PBT and PET (polyethylene terephthalate) hybrids with different contents of organocl are listed in Table 2. 

Engineering thermoplastic resins (ETP) are those whose set of properties (mechanical, thermal, chemical) allows them to be used in engineering applications. They are more expensive than commodity thermoplastics and generally include polyamides (PA), polycarbonate (PC), linear polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyphenylene ether (PPE) and polyoxymethylene (POM). Specialty resins show more specialized performance, often in terms of a continuous service temperature of 200°C or more and are significantly more expensive than engineering resins. This family include fluoropolymers, liquid crystal polymers (LCP), polyphenylene sulfide (PPS), aromatic polyamides (PARA), polysulfones (P ), polyimides and polyetherimides. 

Polyethylene terephthalate is chosen for the polymer - its thermal properties are found in the literature [11]. The values of the diffusivity at high temperature are not known yet, and some assumptions are made from the value at room temperature [12,13] (Table 3.2). 

Koh et al. [15] investigated the mechanical and thermal properties of glass-reinforced polyethylene terephthalate and showed that the molding process used was very important in achieving optimal mechanical properties. 

Dynamic mechanical analysis has also been used to determine the mechanical and thermal properties of low-density polyethylene and ethylene-propylene-diene terpolymer containing jute filler, which had improved flexural and impact properties compared to those of the base polymer [198]. Jeong and coworkers [196] and others [195] investigated the dynamic mechanical properties of a series of polyhexamethyl-ene lerephthalale, poly(l,4-cyclohexylenedimethylene terephthalate), and random copolymers thereof in the amorphous state as a function of temperature and frequency. The effect of copolymer composition on dynamic mechanical properties was examined and the dynamic mechanical properties interpreted in terms of the cooperativity of segmental motions. 

General discussions of the effect of reinforcing agents on the thermal properties of polymers include glass fiber-reinforced polyethylene terephthalate [28], multiwalled carbon nanotube-reinforced liquid crystalline polymer [29], polysesquioxane [30, 31], polynrethane [31], epoxy resins [32], polyethylene [33], montmorillonite clay-reinforced polypropylene [34], polyethylene [35], polylactic acid [36, 37], calcium carbonate-filled low-density polyethylene [38], and barium sulfate-filled polyethylene [39]. 

Until 2003, Chen s [28], Qu s [29-31], and Hu s [32] groups independently reported nanocomposites with polymeric matrices for the first time the. In Hsueh and Chen s work, exfoUated polyimide/LDH was prepared by in situ polymerization of a mixture of aminobenzoate-modified Mg-Al LDH and polyamic acid (polyimide precursor) in N,N-dimethylactamide [28]. In other work, Chen and Qu successfully synthesized exfoliated polyethylene-g-maleic anhydride (PE-g-MA)/LDH nanocomposites by refluxing in a nonpolar xylene solution of PE-g-MA [29,30]. Then, Li et al. prepared polyfmethyl methacrylate) (PMMA)/MgAl LDH by exfoliation/adsorption with acetone as cosolvent [32]. Since then, polymer/LDH nanocomposites have attracted extensive interest. The wide variety of polymers used for nanocomposite preparation include polyethylene (PE) [29, 30, 33 9], polystyrene (PS) [48, 50-58], poly(propylene carbonate) [59], poly(3-hydroxybutyrate) [60-62], poly(vinyl chloride) [63], syndiotactic polystyrene [64], polyurethane [65], poly[(3-hydroxybutyrate)-co-(3-hydroxyvalerate)] [66], polypropylene (PP) [48, 67-70], nylon 6 [9,71,72], ethylene vinyl acetate copolymer (EVA) [73-77], poly(L-lactide) [78], poly(ethylene terephthalate) [79, 80], poly(caprolactone) [81], poly(p-dioxanone) [82], poly(vinyl alcohol) [83], PMMA [32,47, 48, 57, 84-93], poly(2-hydroxyethyl methacrylate) [94], poly(styrene-co-methyl methacrylate) [95], polyimide [28], and epoxy [96-98]. These nanocomposites often exhibit enhanced mechanical, thermal, optical, and electrical properties and flame retardancy. Among them, the thermal properties and flame retardancy are the most interesting and will be discussed in the following sections. 

Chen C., Wang L. and Huang Y. (2008), Morphology and thermal properties of electrospun fatty acids/polyethylene terephthalate composite fibers as novel form-stable phase change materials. Solar Energy Materials Solar Cells, 92 pp. 1382-1387. 

Hydrolysis in polyethylene terephthalate at temperatures of 100 to 120 °C and a relative humidity of 100% takes place approx. 10,000 times faster than thermal degradation, and 5,000 times faster than oxidation in air in the same temperature range. Just 0.01 wt.-% content of effectively acting water at elevated temperatures (100 C) causes a noticeable decrease in molecular mass and viscosity as well as in mechanical properties because of hydrolytic cleavage. This is important in particular for the manufacturing of PET with high molecular masses by solid-phase condensation [774]. 

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