No abstract

SynopsisThe melting and crystallization behavior of Kodar, a copolyester formed from 1,4-cyclohexanedimethanol and a mixture of terephthalic and isophthalic acids, and its miscible blends with polycarbonate was examined. The results of the melting behavior are discussed in terms of crystallization-induced chemical rearrangements and the copolymeric character of Kodar and interchange reactions between components when polycarbonate is present in the blend. For various reasons, the melting behavior cannot be extrapolated to infinite crystal size using the Hoffman-Weeks approach. Crystallization kinetics follows the Avrami equation, with rates being higher when the crystallization temperatuare is approached from the glass rather than from the melt. The kinetic data are discussed in terms of modern theories. An approximate melting point depression analysis is used to estimate the interaction parameter for the blend, and the result obtained is compared to a value from another technique. INTRODUCTIONEarlier r e p o r t~l -~ have shown that the copolyester formed from 1,4-cyclohexanedimethanol and a mixture of isophthalic and terephthalic acids, known commercially as Kodar A-150, is miscible in all proportions with bisphenol A polycarbonate and have described the mechanical,2 t r a n~p o r t ,~ and chemical behavior4 of these blends. The melting and crystallization of the copolyester in these mixtures is of interest for numerous reasons but is complicated by several factors as described more fully here. Melting point depression analysis i s a potentially useful way of characterizing the thermodynamics of mixing miscible polymers5 when one is crystallizable. However, such an analysis may be obscured by variations in crystal size, which also influences the observed melting point. Stein6 has suggested that this effect can be eliminated by extrapolation of the observed melting point versus crystallization temperature to infinite crystal size using the Hoffman-Weeks a p p r~a c h .~ Recent work has shown that various chemical reactions may occur in this ~y s t e m .~ Below the melting point, Kodar apparently undergoes crystallization-induced chemical rearrangements of the type described by Lenz and co-workers≪ while in the melt state, the blend can experience interchange reactions between the components. As shown here, these factors along with perhaps accompanying physical issues frustrate attempts to incorporate the Hoffman-Weeks approach into the analysis of melting point depression for this system.It has been estimated that approximately 20% of the dibasic acid units in Kodar are isophthalic acid: which presumably will not fit into the crystal structure * Present address: Exxon Production Research, Houston, TX.Journal of Applied Polymer Science, Vol. 27,4065-4080 (1982) formed by sequences of terephthalic acid and 1,4-cyclohexanedimethanol units. Therefore, it is of interest to compare the behavior of Kodar with the related polyester, Kodel, which has no isophthalic acid units. The blends used in this work were prepa...

SynopsisBased on the single, composition-dependent glass transition criterion, poly-6-caprolactone (PCL) was found to be miscible with each of four poly(styrene-co-ally1 alcohol) (SAA) copolymers with hydroxyl contents between 1.3 and 7.7 wt %. Melting point depression of the PCL in the blends was used to evaluate the blend interaction parameter B for each miscible system. The parameter B was found to be negative and to vary with copolymer composition in a way that suggests that an optimum density of alcohol moieties in the copolymer exists for achieving maximum interaction with PCL.