Fracture toughness of phenol formaldehyde composites post-cured in microwaves

A commercial phenol formaldehyde based resole thermosetting resin supplied by Borden Chemical Australia Pty. was filled with ceramic-based fillers (Envirospheres "SLG") to increase its fracture toughness. By testing fracture toughness at a range of filler addition levels, the optimal addition level of SLG was able to be determined in terms of workability, cost and performance. The composites obtained were post-cured in conventional oven and in microwaves respectively. It was found that the fracture toughness of the microwave cured composites were up to 37% higher than those cured in conventional oven when the percentage by weight of SLG varies from 0 to 35%. The time required for post-curing was also reduced from 10 hours (in conventional oven) to 40 minutes (in microwaves).