A DYNAMIC FT-IR METHOD FOR DETERMINING THE CURING TEMPERATURE RANGES OF AN ACETYLENE-TERMINATED POLYISOIMIDE PREPOLYMER

A dynamic FT-IR method was used to determine the individual curing tem perature ranges of the isoimide-imide isomerization and crosslinking r eactions of an acetylene-terminated polyisoimide prepolymer. The indiv idual curing temperature ranges of these two types of chemical reactio ns for the polyisoimide system using differential scanning calorimetry (DSC) were totally overlapped. Using dynamic FT-IR spectroscopy, the curing temperature ranges of the isomerization and crosslinking reacti ons were clearly separated. The isomerization reaction began at lower temperatures than the crosslinking reaction and was complete when only half of the crosslinking reaction had occurred. The temperature width , Delta T-1/2, was twice as great for the crosslinking reaction compar ed with the isomerization reaction. Activation energies from dynamic F T-IR spectroscopy can be obtained for the two separate reactions, howe ver, for the reactions considered here, the activation energies were s imilar, 26 kcal/mol for the isomerization reaction and 23 kcal/mol for the crosslinking reaction. (C) 1996 John Wiley & Sons, Inc.