Polyethylene terephthalate transition

Figure 13.6 Resolution of multiple transitions in amorphous polyethylene terephthalate by dielectric thermal analysis, (a) e curves defining polyethylene terephthalate transitions (b) e" curves showing frequency dependency of alpha beta transitions.

Figure 9 Differential scanning calorimetric (DSC) curve showing the phase transitions observed on heating the amorphous form (glass) of polyethylene terephthalate. (Reproduced with permission from Ref. 38.)...

Much more information can be obtained from the DSC experiment than simply an observation of the transition from a solid to a liquid phase. A plot of heat flow against temperature is a true depiction of the continuity of the heat capacity at constant pressure (Cp). If the entire temperature range of a given process is known, the physical state of a material will reflect the usefulness of that material at any temperature point on the plot. For polyethylene terephthalate (see Fig. 4.9), a stepshaped transition is interpreted as a change in Cp resulting from a... 

Meesiri, W., Menczel, J., Gaur, U. and Wunderlich, B. Phase transitions in mesophase macro-molecules. III. The transitions in polyethylene terephthalate-co-oxybenzoate). J. Polymer. Sci., Polymer Phys. Ed., 20, 719 (1982)... 

Edgar, O. B., and E. Ellery Structure-property relationships in polyethylene terephthalate co-polyesters. Part. I. Melting points. Part II. Second-order transition temperatures, J. Chem. Soc. (London) 1952, 2633—2643 J. Polymer Sci. 8, 1—22 (1952). 

Blends of polybutylene terephthalate and polyethylene terephthalate are believed to be compatible in the amorphous phase as judged from (a) the existence of a single glass-transition temperature intermediate between those of the pure components and (b) the observation that the crystallization kinetics of the blend may be understood on the basis of this intermediate Tg. While trans esterification occurs in the melt, it is possible to make Tg and crystallization kinetics measurements under conditions where it is not significant. When the melted blend crystallizes, crystals of each of the components form, as judged from x-ray diffraction, IR absorption, and DSC. There is no evidence for cocrystallization. There is a slight mutual melting point depression. 

Propanediol (1,3PD) is also undergoing a transition from a small-volume specialty chemical into a commodity. The driving force is its application in poly (trimethylene terephthalate) (PTT), which is expected to partially replace polyethylene terephthalate) and polyamide because of its better performance, such as stretch recovery. The projected market volume of PTT under the trade-names CORTERRA (Shell) and Sorona 3GT (Dupont) is 1 Mt a-1 within a few years. In consequence, the production volume of 1,3PD is expected to expand from 55kta-1 in 1999 to 360 kt a-1 in the near future. 1,3PD used to be synthesized from acrolein by Degussa and from ethylene oxide by Shell (see Fig. 8.8) but a fermentative process is now joining the competition. 

Recently Moore and Petrie (5) have demonstrated that control of sample thermal history can result in transition from ductile to brittle behavior for polyethylene terephthalate. This transition in behavior was related to volume relaxation of the glassy state. 

Figure 4.1 Glass transition detection using a polyethylene terephthalate Him clamped onto the surface of a SAW device. (Reprinted with permission. See Ref. [SO]. Copyright 6 1979 Amer-lean Chemical Society.)...

Kanemitsu and Einami (1990) investigated the role of the polymer on hole transport in a series of 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-l,3-oxazole (OX) doped polymers. The polymers were a polyarylate (PA), bisphenol-A polycarbonate (PC), poly(methyl methacrylate) (PMMA), poly(styrene) PS, poly(vinyl chloride) (PVC), polyethylene terephthalate) (PET), and poly(vinyl butyral) (PVB). The glass transition temperatures of the polymers range from 322 (PVB) to 448 K (PA). The temporal features of the photocurrent transients were strongly dependent on the polymer. Figure 76 shows the results. The field was 4.0 x H)5 V/cm and the temperature 295 K. The transients were near rectangular for PS, PET, PA, and PMMA, and highly dispersive for PVC land PVB. This was attributed to the fact... 

In a previous paper (1), phase segregation by spinodal decomposition in mixtures of polyethylene terephthalate and polyhydroxybenzoic acid copolymer (PET-PHB) and polycarbonate (PC) has been investigated. It was shown that thermally induced phase segregation takes place above the Tg of PC and exhibits a lower critical solution temperature (LCST). However, the phase separated domains do not grow until the temperature exceeds 255°C. Some disclinations developed within the liquid crystal rich regions. Even in the pure PET-PHB component, four dark brushes with negative sense of disclinations form around 240°C, indicating the presence of nematic liquid crystals. Paci and coworkers (2) claimed that a smectic-nematic transition exists near 270°C in this liquid crystalline copolyester. 

Figure 10.7 DSC curves of polyethylene terephthalate)-poly(acrylonitrile-butaliene-styrene) (PET-ABS) blends (a) conventional DSC first and second heating curves with heating and cooling rate of lOKmin-1 and (b) temperature modulated DSC (TMDSC) first heating curves with /3=2Kmin 1, p = 60s and 5= 1K. Tg, glass transition temperature. (Reproduced with permission from T. Hatakeyama and F.X. Quinn, Thermal Analysis Fundamentals and Applications to Polymer Science, 2nd ed., John Wiley Sons Ltd, Chichester. 1999 John Wiley Sons Ltd.)...

The binary blends of polycarbonate with polybutylene terephthalate (PBT/PC) or polyethylene terephthalate (PET/PC) are now known to be essentially phase separated blend systems exhibiting two glass transition temperatures in each case, one for the polycarbonate-rich phase, and another for the polyester-rich phase. [Murff et ah, 1984 Huang and Wang, 1986 Wahrmund et ah, 1978]. The evaluation of the amorphous phase miscibility... 

Many crystallizable polymers can be prepared in the amorphous glassy state by rapid quenching as films. Measurements of Aglass transition temperature determined. Such results are shown for amorphous polyethylene terephthalate (PET) in Figure 13 (17). The Brillouin splittings change slope at 70°C. If both Aa>(i) and Awt can be measured, the Poisson ratio (T can be determined according to ... 

The variation of compliances with draw ratio for cold drawn polypropylene filaments examined at 20°C appeared very similar to that of high density polyethylene, with an increase in all compliances but Sii, which was insensitive to draw ratio. Ward aggregate theory was not applicable except for low draw ratios, implying that other processes intervened in addition to an orientation of pre-existing units. It was probable that even above the glass transition temperature increasing orientation led to a reduction in molecular mobility, as was known to occur in polyethylene terephthalate. ... 

Several ingenious explicit versions of, and alternatives to eqns. (3X (5) and (6) have been proposed (Refs. 4, 13-16) which need not be discussed further here. It is sufficient to remark that most of them are purely phenomenological, and apply equally well to amorphous polymers below their glass transition, Tg, e.g. polycarbonate, polymethylmethacrylate, polystyrene, and semi-crystalline polymers both below and above Tg (e.g. polypropylene, polyethylene, polyethylene terephthalate). 

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