PCTAs properties

This report provides an overview of some of the newer polyester compositions based on CHDM. The basic properties and chemistries of PCT have been described in earlier reviews [9, 13]. The CHDM-based polyesters covered in this review are PCT, PCTG, PCTA, and PETG. These compositions are described in more detail in the sections that follow. 

Table 7.3 Physical property comparison of amorphous PETG, PCTG and PCTA...

Although the scope of this review mainly covers CHDM-based polyesters modified with isophthalic acid or ethylene glycol (i.e. PCTA or PCTG, and PETG, respectively), many other copolyesters with interesting properties have been prepared with a variety of other comonomers. 

The properties of PCTA-type structures where the modifying acid is 1,4-cyclohexanedicarboxylic acid (CHDA) have also been studied [53], The incorporation of this diacid (95 % trans) as a polyester modifier maintains the toughness, but is accompanied with significant lowering of the Tg. This is contrasted to NDA modification where the Tg is enhanced but toughness is decreased. A comparison of the properties of various PCTAs versus an amorphous PCT sample, prepared by quenching, are shown in Table 7.5. 

Table 7.5 Comparison of selected properties for various PCTA copolyesters [53]...

Data on the physical and chemical properties of PCDTs and PCTAs are scarce. Due to their structural similarity to PCDFs and PCDDs they are also supposed to possess some likeness in their physical and chemical properties. Sulfur and oxygen are both Group VI elements with two outer shell electrons available for covalent bonding. Structures of thiophene and furan with benzene carbon-sulfur (Cb-S) and carbon-oxygen bond (Cb-0), in PCDTs and PCDFs respectively, suggest similar chemical behavior. The bond dissociation energies (AH) show that less energy is required to break the Cb-S bond than the Cb-0 bond [17,36,37]. 

TABLE 2.4 Comparison of Thermal and Mechanical Properties of PBT, PCX, PCTA, PET, PEG, and PCTG. ... 

Table 4. Physical Property Comparison of Amorphous PETG, PCTG, and PCTA...

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