Enhancement of crack propagation resistance in epoxy resins by introducingpoly(dimethylsiloxane) particles

The physical and mechanical properties of polyepoxy DGEBA/DDA/Diuron networ ks toughened with Poly(dimethylsilorane) particles have been studied. Blend s have been realized with two kinds of dispersion tools: a high-speed stirr er and a twin-screw extruder. The dispersion state quality is discussed usi ng transmission spectroscopy image analysis. Poly(dimethylsiloxane) suspens ion in an epoxy prepolymer was used as a toughening agent. Different partic le quantities were introduced: 4, 8, 15% by weight. Static mechanical tests were performed in tension and compression on these poly(dimethylsilorane) modified materials. A slight decrease of Young's modulus and an increase in plastic deformation capacity were noticed as the volume fraction of the mo difier increased. Using linear elastic fracture mechanics (LEFM), an improv ement in the fracture properties (K-IC, Glc) was shown. Fatigue crack growt h propagation studied for the blends demonstrated that the Paris law can be used to describe the behavior of the materials. Increasing the volume frac tion of the modifier leads to an improvement of fatigue crack propagation r esistance. Finally a decrease in the wear rate and the friction coefficient with the increase of particle quantities has been shown tin a pin on disk configuration). Toughening mechanisms are discussed with SEM fracture surfa ces. (C) 1999 Kluwer Academic Publishers.