Tetramethylene terephthalate

In this review the definition of orientation and orientation functions or orientation averages will be considered in detail. This will be followed by a comprehensive account of the information which can be obtained by three spectroscopic techniques, infra-red and Raman spectroscopy and broad line nuclear magnetic resonance. The use of polarized fluorescence will not be discussed here, but is the subject of a contemporary review article by the author and J. H. Nobbs 1. The present review will be completed by consideration of the information which has been obtained on the development of molecular orientation in polyethylene terephthalate and poly(tetramethylene terephthalate) where there are also clearly defined changes in the conformation of the molecule. In this paper, particular attention will be given to the characterization of biaxially oriented films. Previous reviews of this subject have been given by the author and his colleagues, but have been concerned with discussion of results for uniaxially oriented systems only2,3). 

PTT is made by the melt polycondensation of PDO with either terephthalic acid or dimethyl terephthalate. The chemical structure is shown in Figure 11.1. It is also called 3GT in the polyester industry, with G and T standing for glycol and terephthalate, respectively. The number preceding G stands for the number of methylene units in the glycol moiety. In the literature, polypropylene terephthalate) (PPT) is also frequently encountered however, this nomenclature does not distinguish whether the glycol moiety is made from a branched 1,2-propanediol or a linear 1,3-propanediol. Another abbreviation sometimes used in the literature is PTMT, which could be confused with poly(tetramethylene terephthalate),... 

Figure 12.4 Structures of polyesters with longer aliphatic chains (a) poly(tri-methylene terephthalate) (PTT) (b) poly(tetramethylene terephthalate) (PBT)...

Copoly(ether ester)s consisting of short-chain crystalline segments of PBT and amorphous poly(ether ester) of poly(tetramethylene terephthalate) exhibit a two-phase structure and can be used for the production of high-impact-strength engineering plastics. These very interesting materials with their outstanding properties understandably require stabilization to heat and UV exposure [45],... 

A Comparison of Published Structures of Poly(tetramethylene terephthalate)... 

This is illustrated by the case of poly (tetramethylene terephthalate) (4GT). Three independent determinations have been made of the crystalline structure of the cx-phase of this material. (1,2,3). The conformation angles are given in Table I (see Figure 1 for key) from which it will be seen that they all... 

Figure 9 shows the dynamic mechanical spectra of a series of poly-(tetramethylene oxide) /poly (tetramethylene terephthalate) (PTMO/ PTMT) segmented copolymers (67). These materials reveal only one Tg and one Tm analogous to semicrystalline thermoplastics. The magnitude of both transition temperatures shifts progressively higher with increasing... 

Studies have been conducted on poly (tetramethylene oxide )-poly-(tetramethylene terephthalate) -segmented copolymers that are identical in all respects except for their crystalline superstructure (66,67,68). Four types of structures—type I, II, and III spherulites (with their major optical axis at an angle of 45°, 90°, and 0° to the radial direction, respectively), and no spherulitic structure—were produced in one segmented polymer by varying the sample-preparation method. Figures 10 and 11 show the stress-strain and IR dichroism results for these samples, respec-... 

T nterest in polyether-ester block copolymers that are both thermoplastic - and elastomeric continues at a sustained pace (1-9). Most of the recent communications have dealt with the tetramethylene terephthalate/ poly(tetramethylene ether) terephthalate copolymers which are continuing to find increased use in commercial applications requiring thermoplastic elastomers with superior properties. 

Part I of this series explored the structure-property relationships of tetramethylene terephthalate/polyether terephthalate copolymers as a function of variations in the chemical structure, molecular weight, and concentration of the polyether units (10). Of the polyether monomers tested, poly (tetramethylene ether) glycol of molecular weight approximately 1000 was found to provide copolymers having the best overall combination of physical properties and ease of synthesis. 

Copolymer compositions are expressed as weight percentages of the ester units with the remainder being polyether-ester units. For instance, 40% tetramethylene terephthalate/PTME terephthalate copolymer represents a block copolymer containing 40 wt % of tetramethylene terephthalate units and by difference 60 wt % of poly(tetramethylene ether) terephthalate units. 

Polymer compositions are based on the ratios of starting monomers on the assumption of no loss of monomers during copolymerization other than the deliberate removal of the excess diol needed to drive the copolymerization to completion. The polymerization procedures are believed to result in block copolymers composed of a random distribution of components (12,13). The block structures of these copolymers are attributed to the use of PTME glycol as one of the monomers. X-ray diffraction studies of tetramethylene terephthalate/PTME terephthalate copolymers have verified the presence of crystalline tetramethylene terephthalate segments and the apparent lack of crystallinity of the PTME terephthalate segments (14). 

The concentration of crystalline ester segments in tetramethylene terephthalate/PTME terephthalate copolymers has a major effect on physical properties. Copolymers were prepared and tested which covered a range of tetramethylene terephthalate (4GT) concentrations from a low of 30% to a high of 82% (Table I). 

Table I. Tetramethylene Terephthalate/PTME Terephthalate Copolymers—Properties as a Function of Tetramethylene Terephthalate Content (36)...

The structure of the diol in alkylene terephthalate/PTME terephthalate copolymers has an important effect on the properties of these block copolymers, as evident from the results shown in Tables II, III, and IV. The 50% tetramethylene terephthalate/PTME terephthalate copolymer prepared from 1,4-butanediol (4G) which was previously noted in Table I serves as our reference copolymer for purposes of discussing the effects of changing the structure of the crystallizable ester segments. The outstanding properties of the 4G-based copolymer are ease of synthesis, a rapid rate of crystallization from the melt, a high melting point, and excellent tensile and tear strengths. 

Figure 2. Permanent set at break as a percentage of elongation at break vs. the wt % of tetramethylene terephthalate segments in tetramethylene terephthalate/PTME terephthalate copolymers (36)...

Up to this point the discussion has been concerned with alkylene terephthalate/PTME terephthalate copolymers in which the concentration of alkylene terephthalate and the chemical structure of the alkylene groups have been varied. The next section of this report is concerned with polyether-ester copolymers in which aromatic esters other than terephthalate are used in combination with PTME glycol and various diols. The objective is the same, to correlate changes in copolymer structure with changes in copolymerization results and copolymer properties. Once again the 50% tetramethylene terephthalate/PTME terephthalate copolymer (Tables I and II) with its excellent properties and relative ease of synthesis will be used as the point of reference to which the other polymers will be compared. 

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