The results showed that the fracture surface of the modified systems displayed toughfracture features, markedly different from that of the unmodified epoxy resin system.
For the UPR with greater brittleness, the brittle-tough transition was observed only when the toughness of the resin was characterized by fracture toughness at a slower loading rate.
对于脆性较大的UPR，只有在采用加载速度较慢的断裂韧性来表征其韧性时，方能观察到这一脆韧转变现象。
3
The impact fracture surface showed a tough morphology for POM/NBR/Novolak blends and brittle one for POM/NBR blends.