Premium
Development of crystallinity in NEW‐TPI polyimide
Author(s) -
Friler Jerome B.,
Cebe Peggy
Publication year - 1993
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760331003
Subject(s) - materials science , crystallinity , polyimide , composite material , polymer science , layer (electronics)
Development of crystallinity in NEW‐TPI semicrystalline polyimide has been studied using differential scanning calorimetry (DSC), wide (WAXS), and small angle X‐ray scattering (SAXS). Crystallinity of the fully imidized powder, pellet, or film processed NEW‐TPI can occur from the melt, and depends upon the holding temperature of the melt. Repetitive exposure to elevated temperatures supresses the development of crystallinity from the melt state. In amorphous pellets and film, crystallinity can also develop by cold crystallization from the rubbery amorphous state. SAXS results show that during cold crystallization, NEW‐TPI develops a periodic structure consistent with formation of alternating crystalamorphous stacks, but with crystals only a few molecular repeat units thick. Kinetics of nonisothermal crystallization were studied as a function of heating rate and could be described using the Ozawa analysis. Non‐isothermal crystallization proceeds at a slower rate in NEW‐TPI than in other high temperature thermoplastics such as PEEK, and with a much narrower processing window. The maximum degree of crystallinity that could develop during heating was 0.34, which occurred at a rate of 5°C/min. Similar degrees of crystallinity could be introduced by heating amorphous NEW‐TPI film in N‐methylpyrrolidone.