Effect of Nano and Fiber Fillers on Polymerization Shrinkage

Objectives: The aim was to evaluate the effect of different nanofiller fractions and temperature on polymerization shrinkage strain and degree of monomer conversion of short glass fibres reinforced semi-IPN polymer matrix composite resin.

Methods: Experimental composite resin (Group A) was prepared by mixing 22.5 wt% of short E-glass fibres (3 mm in length) to resin matrix with various weight fractions of nanofillers (0, 10, 20, 30, 40, 50 wt%) with additional micrometer scale silica fillers using high speed mixing machine. Group  B contained composite resin prepared by mixing resin matrix without nanofillers to 77.5 wt% of silica filler particles without fibre fillers. As control material (Group C), commercial particulate filler composite resin (Grandio, VOCO) was used. The shrinkage strain of the specimens was measured using the bonded-disc technique at 26 and 37°C with respect to time. Additionally degree of conversion of studied groups were measured using FTIR spectroscopy.

Results: ANOVA revealed that fraction of nanofillers and polymerization temperature had significant effect (P<0.001) on the shrinkage strain and degree of conversion of the composite resin.

Conclusions: It was concluded that by adding particulate nanofillers to short glass fibre reinforced composite resin with semi-inter penetrating polymer network matrix lowered the polymerization shrinkage strain of the composite.