Sample [T.sub.o](a) [T.sub.P] (a) [T.sub.f] (a) [DELTA]E ([degrees]C) ([degrees]C) ([degrees]C) (kJ/mol) Neat resin 210 256 292 87 PPEK 5-phr 207 255 293 86 PPEK 10-phr 208 252 286 78 PPEK 15-phr 208 256 294 80 PPEK 20-phr 220 257 281 95 (a) The results were determined by DSC measurements at heating rate of 10 K/min.
When PPEK was introduced, the activation energy of the cure reaction had no obvious change.
and 20-phr PPEK blends, which would aid in designing materials by the control of structure development in multicomponent thermosetting resins.
The phase evolution process in 10-phr PPEK blend was shown in Fig.
Figure 6 showed the phase separation process in 15-phr PPEK blend.
The critical stress intensity factor reached the maximum at 10-phr PPEK, [K.sub.IC] was increased from 1.36 MPa.[m.sup.[1/2]] for the neat BMI resin to 1.64 MPa-[m.sup.[l/2]] for the 10-phr PPEK blend.
The morphology of the cured blends exhibited a continuously transition from a spherical particle structure to a phase-inverted structure with the increase of the PPEK content.
The fracture surfaces of 5- and 10-phr PPEK blends (Fig.