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Influence of stereochemistry on the thermal properties of partially cycloaliphatic polyamides

par Vanhaecht, Bert;Rimez, Bart ;Willem, Rudolph ;Biesemans, Monique;Koning, Cor
Référence Journal of polymer science. Part A, Polymer chemistry, 40, 12, page (1962-1971)
Publication Publié, 2002-06

Article révisé par les pairs

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Résumé :

The effects of the partial substitution of 1,4-disubstituted cyclohexane monomers for linear aliphatic monomers in polyamides are discussed. More specifically, the relation between the stereochemistry of the cycloaliphatic residues and the thermal properties [melting temperature (Tm) and crystallization temperature (Tcr)] was investigated. For this purpose, two different types of copolyamides were synthesized: in polyamides 12.6, the adipic acid residues were partially replaced by cis/trans-1,4-cyclohexanedicarboxylic acid (1,4-CHDA), whereas in polyamides 4.14, the 1,4-diaminobutane residues were partially substituted with cis/trans-1,4-diaminocyclohexane (1,4-DACH). For both Systems, increasing the degree of substitution of cycloaliphatic residues for linear aliphatic residues resulted in a rise of both Tm and Tcr. This points to the isomorphous crystallization of the linear and cycloaliphatic residues. In contrast to the use of 1,4-DACH as a comonomer, 1,4-CHDA residues showed isomerization upon thermal treatment of the polyamides. This isomerization of the cyclohexane residues influenced the thermal properties of the copolyamides. The use of a nonisomerizing cis-trans mixture of 1,4-DACH exhibited the large influence of the stereochemistry of the cycloaliphatic residues on the Tm of the copolyamides. For both the 1,4-CHDA- and 1,4-DACH-based copolyamides, differential scanning calorimetry analysis revealed that recrystallization occurs during melting. This exothermal effect becomes less pronounced with an increasing content of rigid cycloaliphatic residues. © 2002 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym. Chem.