Studies on the phase transition and thermal stability of Xydar and Zenite series liquid crystalline polymers

Abstract

Four commercially available main‐chain LCPs, Xydar and Zenite series, are characterized by FTIR spectroscopy, DSC, polarized light microscopy (PLM), TGA, TGAFTIR, and elemental analysis. The FTIR spectrum of Zenite 8000B is found to be more similar to that of Vectra A950 than those of the other three LCPs. Xydar SRT900 and 1000 have almost the same FTIR spectra. Zenite LCPs have broader crystal‐mesophase transition (TCM) and less clear liquid crystalline textures at TCM than those of Xydar LCPs. Xydar SRT1000 and Zenite 8000B have lower TCM than Xydar SRT900 and Zenite 6000, respectively. For all the four LCPs, the glass transitions can not be easily observed by DSC without the aid of annealing and the isotropic phase does not appear before thermal degradation. Xydar SRT1000 and Zenite 8000B have lower thermal stabilities as well as lower TCMS than Xydar SRT900 and Zenite 6000, respectively. It is interesting to find that Ea (Apparent activation energy of thermal degradation) curv of Xydar SRT900 and SRT1000 have the similar shapes as those of Zenite 6000 and 8000B, respectively. For the first time, we have found that there is a minor degradation maximum for Zenite 8000 at about 2.5% weight loss in N2. For all the four LCPs, the Ea values in an air atmosphere begin to decrease at a temperature close to the deflection points on the first derivative curves. The first stage of the thermal degradation in an air atmosphere has similar mechanisms as that in N2.

Flexible all‐aromatic polyesterimide films with high glass transition temperatures

“…After processing, the reactive end‐groups are allowed to chain extend or crosslink in a successive high‐temperature post‐treatment step. This route yields polymers with good thermomechanical properties including high tensile strengths (83 MPa) and elongation at break (9%) …”

Peculiarities of The Orientational State of Liquid-Crystal Completely Aromatic Thermotropic Copolymer

“…The IR-spectra of Vectra A950 in the range of 4000-400 cm-1 are shown in Figure 1. The absorption bands in these spectra were assigned in [5,13]. Far-IR spectra of Vectra A950 in the range 480-20 cm -1 are shown in Figure 2.…”

Особенности Локальной Динамики И Ориентационного Состояния Жесткоцепных Жидкокристаллических Полимеров

“…1. Отнесение полос в этих спектрах сделано в работах [9,12]. Спектры среднего ИК-диапазона (в том числе и поляризационные) этих образцов оказались практически одинаковыми, видимо потому, что короткодействующие внутримолекулярные силы в нитях существенно не отличаются от таковых в гранулах.…”