Effect of tannin on flexural properties of phenol formaldehyde glycerol reinforced composites: preliminary results

Abstract

Phenol formaldehyde composites are modified with glycerol/tannin mixes with varying percentage by weight of phenolic resin to glycerol/tannin. The glycerol to tannin ratio is also varied. In this work also different percentages by weight of SLG (a commercial ceramic microsphere) are added to the composites. The effect of glycerol/tannin mix and added SLG on the flexural properties was studied. It was found that the flexural stress decreases gradually with increasing tannin when there is no SLG. With SLG, the presence of tannin in the composites reduces the flexural stress drastically. Tannin reduces the strain at break. With SLG, this reduction of the yield strain is more apparent. Tannin increases the flexural modulus of the composite and SLG acts in the opposite direction. The use of tannin in the phenolic composites improves the ‘green’ character of the composite materials. It was also found that the presence of tannin made the mixing of phenolic resins with glycerol easier.