The influence of poly(acrylic acid) molar mass and concentration on the properties of polyalkenoate cements - Part III - Fracture toughness and toughness

The influence of poly(acrylic acid), PAA molar mass and concentration on fr acture toughness and toughness of glass polyalkenoate cements was investiga ted. Fracture toughness and toughness increased with both the molar mass of the PAA and its concentration. The fracture toughness and toughness increa sed dramatically with concentration for the highest molar mass PAA studied. However the increase in fracture toughness and toughness with PAA concentr ation was small for the lowest molar mass PAA. The influence of molar mass was greatest at the highest PAA concentration studied and least for the low est PAA concentration. The toughness results were analysed with a reptation chain pull-out model. The greater dependance of toughness on PAA concentra tion for high molar mass cements can be explained by the critical molar mas s for chain entanglements to form (M-e) being concentration dependant and M -e decreasing with increasing PAA concentration. (C) 2001 Kluwer Academic P ublishers.