Abstract
Properties of cured high molecular phenolic resins (HMPR) with hydroxymethyl groups were investigated.
The structural analysis of HMPR by the measurement of nuclear magnetic resonance led us to following findings : HMPR is high molecular phenolic resin with a low crosslinking density, and has 0.10 piece of hydroxymethyl group per benzene ring.
Physical properties of the cured HMPR were examined by the dynamic viscoelastic measurement, and the of flexural strength and charpy impact strength tests. The crosslinking density (ρ) could be calculated using a rubber elasticity equation because of the cured HMPR showing a flat rubbery state in viscoelastic property. The relationship between ρ and physical properties was investigated for the cured HMPR having different ρ values. The conclusions were : the glass transition temperature (Tg) and the flexural strength increased with increasing ρ, and the strength reached the maximum value when ρ was 2.12 × 10-2mol/ cm3.
It was shown that the cured HMPR had a larger impact strength than the cured novolac with the same Tg value.
