Mechanical properties and structural transitions in the new rigid-rod polymer fibre PIPD ('M5') during the manufacturing process

摘要

The polymer poly(2,6-diimidazo [4,5-b:4',5'-e]pyridinylene-1,4(2,5-dihydroxy)phenylene} (PIPD) is spun from a liquid crystalline solution in polyphosphoric acid. The as-spun fibre is a crystal hydrate, which transforms into a bidirectional hydrogen-bonded structure during heat treatment. This transition results in an increase in crystalline modulus along the chain direction due to a decrease of the cross-sectional area per chain, and in an increase in shear modulus due to stronger interaction between the chains caused by the hydrogen bonds. Heat-treated PIPD has a tensile modulus up to 360 GPa, a tensile strength well above 4 GPa, an internal shear modulus of 7 GPa, and a compressive strength of 1.7 GPa. (C) 1998 Elsevier Science Ltd. All rights reserved. [References: 21]