PET copolymers

Poly(ethylene oxide)—Poly(ethylene terephthalate) Copolymers. The poly(ethylene oxide)-poly(ethylene terephthalate) (PEO/PET) copolymers were first described in 1954 (40). This group of polymers was developed in an attempt to simultaneously reduce the crystallinity of PET, and increase its hydrophilicity to improve dyeabiHty. PEO/PET copolymers with increased PEO contents produce surfaces that approach zero interfacial energy between the implant and the adjacent biological tissue. The coUagenous capsule formed around the implant is thinner as the PEO contents increase. The stmcture of a PEO/PET copolymer is shown below ... 

A family of PEO/PET copolymers has been synthesized and the characterized stmctures found to be close to those expected in theory (41). A wide degradation envelope has been achieved by adjusting the PEO-to-PET ratio. Mechanical properties prove useful for medical appHcations, and the 60/40 PEO/PET composition is reported as optimal. 

Reed AM and Gilding DK. Biodegradable polymers for use in surgery-poly(ethylene oxide) poly (ethylene terephthalate) (PEO/PET)copolymers 2. in vitro degradation [J]. Polymer, 1981, 22,499-504. Van Blitterswijk CA, Brink JVD, Eeenders H, et al. The effect of PEG ratio on degradation, calcification and bone bonding of PEO/PBT copolymer (Polyactive). Cell Mater, 1993, 3(1), 23-36. 

PET COPOLYMERS WITH INCREASED MODULUS AND THERMAL PROPERTIES... 

Table 6.1 Thermal properties of PET copolymers containing 10mol% of various x, 4/-bibenzoic acids as comonomers...

Another PET copolymer system that was recently demonstrated to be sufficiently stable to standard synthesis conditions, yet photochemically reactive, is that of PET-/ -phenylene bisacrylic acid (PBA) (Figure 6.9) [74], Upon UV irradiation, PET copolymers containing up to 15mol% of PBA were shown to irreversibly undergo [2 + 2] cycloaddition reactions to produce lightly crosslinked, amorphous materials. 

It was previously mentioned was that a large number of minor copolymers of PET have been developed over the past 50 years, with the intent of modifying textile fiber properties and processability [2, 3], Of broader interest is that some of these textile modifications, such as PET copolymers with metal salts of 5-sulfoisophthalic acid (SIPA), have their own rich chemistries when the extent of polymer modification is increased beyond textile levels. An example of such a modification is that changing the counterions associated with SIPA can significantly effect the kinetics of polyester transesterification reactions (the... 

Figure 12.13 Structure of a PET copolymer with adipic acid, used for deep-dye fibers...

To understand the nature of the microstructures that are present in these systems it is important to start by examining the role of the synthetic route in preparing these copolyesters. In the case of the PHBA/PET copolyester, this system presents a degree of complexity which is unusual. In the mid seventies, Jackson and Kuhfus reported that this system was random, but they did not comment on the possibility of compositional variations [2]. Fortunately, because of the modest solubility of this system, most of the confusion has recently been eliminated through detailed NMR studies [9]. Thus, it has been shown that the 60/40 PHBA/PET copolymers originally available from Tennessee Eastman actually consisted of two distinct compositions, namely 44/56 and 62/38 PHBA/PET (see Fig. 11). Furthermore, the soluble PET rich fraction ( 20%) was shown to be blocky while the insoluble PHBA rich fraction (80%) was more random (see Fig. 12). These observations can be explained from a... 

Recently [58], polyesters have been prepared from dimethylterephtalate, ethylene glycol and the diester CH302C—RF—O —RF—C02CH3. The copolycondensation by transesterification was studied and the authors investigated the morphology, the thermal and surface properties of these obtained polyesters. We can notice that the PET/copolymer (PET —PFPE) blend thus obtained contains up to 35% in weight of PFPE but 7% only are bond with the prepared PET. 

Barrier over-wrapping film for food PET copolymer Office Media... 

Among the many different classes of thermotropic polymers, only a limited number of polyesters based on aromatic ester type mesogenic units have been studied by rheological methods, beginning with the publication by Jackson and Kuhfuss of their work on the p-oxybenzoate modified polyethylene terephthalate, PET, copolymers. They prepared a series of copolyesters of p-hydroxybenzoic acid, HBA, and PET and measured the apparent melt viscosity of the copolymers as a function of their composition by use of a capillary rheometer. On inclusion of low levels of HBA into PET, the melt viscosity increased because of partial replacement of the more... 

Jerman and Baird recently conducted rheological studies on the same copolymers using an Instron capillary rheometer. They also measured die swell and entrance pressures. They observed that the viscosity of the 60 mole % HBA/PET copolymer was two orders of magnitude lower than that of PET when compared at the same temperature of 285 °C, which is similar to the results reported earlier by Jackson and Kuhfuss Die swell of the copolymers was highly temperature dependent. In general,... 

Type-2 copolyesters were synthesized by melt polycondensation of 4-acetoxybenzoic acid (HBA) and 6-acetoxy-2-naphthoic acid (HNA) (Calundann, 1979). While the 4-acetoxybenzoic acid tends to form P(HBA) blocks in certain cases such as in the copolymers of HBA/BP/TA/IA discussed in the previous section, and in HBA/PET copolymers to be discussed in the next section, a random distribution is readily achieved in HBA/HNA copolymers because the two monomers have about the same reactivity toward copolymerization. As shown in Figure 5.3, the 2,6-naphthalene... 

Special models have been developed for the crystallization of these and related stiff-chain aromatic copolymersThe basic crystal was suggested to be of the condis crystal type with rotational disorder based on conformational mobility, proven by mechanical and dielectric relaxation The morphology of the superimposed crystals was proposed to be based on a matching of order between adjacent molecules similar to cold crystallization originally proposed for the crystallization of PET-copolymers from the glassy state... 

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