A STUDY OF THE CURING BEHAVIOR OF AROMATIC POLYAMIDE FIBER EPOXY COMPOSITES TIME-TEMPERATURE-TRANSION STATE DIAGRAM AND CURING KINETICS

Based on the curing temperature,three types of behavior of various surface characterized PPTA fiber/epoxy systems were observed,(Ⅰ) below T_gg(the glass transition tem perature of the reaction systems at the gel point) only vitrification come about;(Ⅱ) between T_gg and T_g∞(the glass transition temperature of the ultim ately cured polymers)both gelatinization and vitrification come about,and(Ⅲ)above T_g∞,only gelatinination takes place.Overall activation energies and apparent overall rate constant of the curing reactions for various surface characterized PPTA fiber/epoxy systems based on third-order overall kinetics were determined before gelation,after gelation but before vitrification and after vitrification,from the gelation time,relative rigidity and glass transion temperature Tg(t) of the polymers as the kinetic terms.The influence of the curing temperature and surface property of the fibers on the kinetic parameters is discussed.Based on various relative rigidity and damping curves vs.time under isothermal conditions,we obtained Time-Temperature-Transition(T.T.T.) state diagrams of various surface characterized PPTA.fiber/apoxy systems.These state digrams (T.T.T.)can be used in formulating the curing technology for various kinds of fiber reinforced epoxy composites.