Phase behavior of blends of poly(ethylene terephthalate) with liquid‐crystalline polymers

Abstract

Poly(ethy1ene terephthalate) (PET) was melt blended with several liquid-crystalline polymers (LCPs), both with and without Ti(OBu), catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra-A950, Rodrun LC-5000, Rodrun LC-3000, and a laboratory copolyester of sebacic acid (S), 4.4'-diacetoxybiphenyl (B), and 4-acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by diEerential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET-rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase.

Ester Exchange Reactions in Equimolar Poly(ethylene terephthalate)/Poly(phenylene sebacate) Blends

“…The formation of the mesophase, as the only ordered phase in the system, provides the enthalpy driving force for reorganization and makes the composition of the two phases become progressively more different as reactions proceed. The segregation of a highly aromatic phase within the aliphaticrich matrix, clearly resulting from compositional differentiation, has also been observed, though more slowly because of the much lower concentration of reactive functional groups, during the reactive blending of PET and preformed LCP, [27] thus confirming the above conclusion.…”

Sequence analysis and fiber properties of a blend of poly(ethylene terephthalate) and poly(ethylene terephthalate‐co‐4,4′‐bibenzoate)

“…This is different from blends of PET with Rodrun™, in which the products of transesterification can cocrystallize with PET such that the heat of fusion does not change upon reactive blending. 12 With complete randomization, the PET/ PETBB55 blend becomes random PETBB15, which does not crystallize. Blends of PET and PEN display similar behavior such that the degree of randomness is not a controlling factor to thermal properties of the blend after a certain level of transesterification has been achieved.…”

“…However, PET and LCPs are often incompatible and the rates of transesterification in melt blended samples of PET with liquid crystalline polyesters depend on the flexibility of the LCP. 12 The work described herein attempts to reinforce PET with a more compatible blend component. 13 C-NMR spectroscopy has been used to determine the relative amounts of differing monomer dyads in copolyesters 6,13 in cases in which 1 H-NMR spectroscopy is insensitive to copolymer sequence.…”

New PET-Based Liquid Crystalline Copolyesters and Their Use in Blends and Composites

“…Moreover, a slight decrease of the fusion temperature T m measured during the second heating run is determined for the p(ET)-p(ETHB) blends, but not for those with VA. On the contrary, no appreciable effect of the presence of any of the LCPs on the enthalpy changes associated with the fusion/crystallization transitions could be observed. In a previous work, [26] some of us investigated the phase behavior of blends of p(ET) with various LCPs, namely VA and other p(ET)-based copolyesters including Rodrunm LC3000 and Rodrunm LC5000 and found that none of the LCPs is miscible with p(ET), although slight interphase interactions could be shown to occur between the p(ET) matrix and all the semi-flexible LCPs. Similar conclusions can be drawn from the DSC investigation of the polymer blends presented in Table 4.…”