The phase strticture and relaxation phenomena in blends of a poly(ether-ester)
elastomer with a liquid crystalline polyester (Vectra)
Polimery 2002, No 1, 34
Poly(ether-ester) (PEE) Elitel 4450 — liquid crystalline polyester (LCP) Vectra RD 501 blends extruded (L/D = 20, D = l9 mm) with a homogenizing head at 225 °C, were studied by differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), dielectric spectroscopy, and scanning electron microscopy (SEM). The blends exhibited a multiphase microstructure. Two mechanical relaxation temperatures were found to occur, and similarly two glass transition temperatures were recorded by DSC. There is a glass transition in the PTMO soft phase (ca. – 60 °C) and in Vectra (+ 107 °C). For the PBT bard phase (ca. +35 °C), Tg2 is weakly pronounced because of the high crystallinity. The blend showed only one m.p., close to the m.p. of the PEE. Three dielectric relaxation processes were found to occur in PEE and three others in Vectra. In the blends, the dielectric spectra are seen to be superimposed. These blends are immiscible in terms of thermodynamics. Vectra modified the molecular mobility of the PEE rigid segments, as evident from nonisothermal crystallization of the PBT hard phase and degree of crystallinity as also from changes of the PTMO content in the soft phase. SEM disclosed either a spherical or a fibrous structure in the blends, depending on Vectra content.
Keywords: block copoly(ether-ester), liquid crystalline polyester, polymer blends, Elite14450—Vectra RD 501 blends, phase structure, physical properties, relaxation phenomena, molecular mobility