Monitoring the reaction progress of a high‐performance phenylethynyl‐terminated poly(etherlmide). Part II: Advancement of glass transition temperature

Abstract

The cure schedule for carbon fiber-reinforced, phenylethynyl-terminated UltemTM (GE Plastics) composites was studied in an attempt to optimize the resultant glass transition temperature, Tg Reaction progress and possible matrix degradation were monitored via the Tg On the basis of previous research, matrix degradation induced Tg reduction was expected for increases in cure time or temperature beyond approximately 70 minutes at 350°C. Using the central composite design (CCD) of experiment technique, composite panels, neat resin, and polymer powder-coated tow (towpregl were cured following various cure schedules to allow for the measurement of the glass transition temperatures resulting from cure time and temperature variations. The towpreg and neat resin specimens were cured in a differential scanning calorimeter. The glass transition temperatures of all specimens were measured via differential scanning calorimetry; the composite glass transition temperatws were also measured with dynamic mechanical thermal analysis. The composite panels and towpreg specimens showed similar trends in Tg response to cure schedule variations. Composite and towpreg glass transition temperatures increased 'to a plateau with increasing cure time and temperature, whereas, the neat resin showed an optimal Tg followed by Tg reduction with increasing cure time and temperature. The optimal neat resin Tg occurred within a cure time and temperature significantly below that required to maximize the composite and towpreg glass transition temperatures.

Molecular weight controlled poly(amic acid) resins end‐capped with phenylethynyl groups for manufacturing advanced polyimide films

“…The T g of the thermal‐cured PI film is 412.4 °C, up about 85 °C from the uncured one heated at 300 °C, and then declines considerably to 354 °C with further rising the final curing temperature to 450 °C. This results resemble the study by Bullions et al ., wherein the addition‐type imide oligomers demonstrated an optimal T g followed by T g reduction with increasing curing temperature. Hence, the curing reaction of phenylethynyl moiety at the PI chain‐ends has been completed at 400 °C.…”

“…It is noteworthy that the aggregation structure of PI film is intensely affected by the variables that control the thermal‐curing process, e.g. temperature and time, which in turn would directly play a critical role in dictating mechanical and thermal properties . It was expected that thermal transitions and concomitant morphology changes caused by the thermal‐activated, free‐radical‐predominant curing of phenylethynyl functional group under various processing conditions should be indicative of the curing behavior and mechanical response of PI films.…”

“…In Figure 10( 35 wherein the addition-type imide oligomers demonstrated an optimal T g followed by T g reduction with increasing curing temperature. Hence, the curing reaction of phenylethynyl moiety at the PI chain-ends has been completed at 400 8C.…”