PCTA copolyester

PCTA Copolyester. Poly(l,4-cyclohexanedimethylene terephthalic acid) (PCTA) copolyester is a polymer of cyclohexanedimethanol and terephthalic acid, with another acid substituted for a portion of the terephthalic acid otherwise required. It has the following formula ... 

PCTA likewise refers to an acid-modified PCT copolyester. Isophthalic acid (IPA), or alternatively the dimethyl ester of IPA, is the most commonly used modifying dibasic acid to prepare PCTA copolyesters. PCTA thus refers to PCT compositions modified with up to 50 mol% IPA. The PCTA structure is as follows ... 

Figure 7.10 Transparent toy kaleidoscopes molded from Eastman Durastar 1010 PCTA copolyester. Photograph provided by courtesy of Eastman Chemical Company...

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

When the terephthalic units of PCT are partially replaced by isophthalic ones, another commercial aromatic copolyester family is obtained (PCTA) (Figure 6.11). These copolyesters are usually obtained by polycondensation of DMT and DMI mixtures with 1,4-CHDM (11,52). The incorporation of small amounts of isophthalic units (5-10 %) in PCT reduces both its melting temperature and enthalpy which makes it more easily processable. Increasing amounts of isophthalate units in PCTA copolyesters gave place also to a decrease in the glass transition temperature. When the content in such units comes over 35%, the copolyesters are amorphous (11). These copolyesters are though, transparent and resistant to hydrolysis and chemical attack, and have been termed as easy dry copolyesters (1). 

CHDA CHDM DMCD EG IPA N NDA PCT PCTA PCTG PET PETG TMCD TPA cis/trans-1,4-cyclohexanedicarboxylic acid cis/trans-1,4-cyclohexanedimethanol dimethyl cis/trans-1,4-cyclohexanedicarboxylate ethylene glycol isophthalic acid dimethyl 2,6-naphthalenedicarboxylate 2,6-naphthalenedicarboxylic acid poly(1,4-cyclohexylenedimethylene terephthalate) dibasic-acid-modified PCT copolyester glycol-modified PCT copolyester poly(ethylene terephthalate) CHDM-modified PET copolyester c .S / ra .v-2,2,4,4-tetramethyl-l,3-cyclobutancdiol terephthalic acid... 

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. 

PCTA CHDM-PTA copolyester PE-MD polyethylene-medium density (also... 

A closely related family of copolyesters is PCTN these are obtained in a similar manner as PCTA but using dimethyl 2,6-naph-thalenedicarboxylate in place of DMI (Figure 6.11). These copolyesters have been prepared also by polycondensation using the bis(hydroxyethyl) derivatives and the optimal conditions for this synthesis have Ijeen reported (53). 

Figure 6.11 Chemical structure of PCTA and PCTN copolyesters.

The behavior of PCTN copolyesters is however very dissimilar to that of PCTA. An increase in naphthalate units entails an increase in T, and displays an eutectic behavior with the minimum at 40 %mol of such units, approximately. A study made on the crystallization of these copolyesters revealed that they are isodimorphic (54). 

For copolyesters with CHDM as the unique diol, the replacement of the diacid unit provokes similar effects. In some cases, as for example PCTN copolyesters there is an eutectic point at 40 % of naphthalate units. In the case of PCTA, the copolyesters is amorphous for contents in isophthalate units above 40% (52,54). 

The first blends studied on polyesters based on 1,4-CHDM were made of the amorphous copolyester of terepthalic and isophthalic acids and 1,4-CHDM (PCTA) and polycarbonate of bisphenol A (126). The single displayed for the whole range of compositions was taken as demonstrative of full miscibility, which is explained as due to the positive physical interactions between the polyester and the polycarbonate. PCTA is also miscible with a copolycarbonate of bisphenol A and l,l-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclo hexanone (TMC) for all compositions except for those involving a polycarbonate entirely made of TMC (127). 

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