Mechanical properties and chemistry of carbonization of Phenol formaldehyde resin

Phenol formaldehyde precursors in the form of powder and 1 mm thick platelets were carbonized in flowing nitrogen up to 1000°C with a heating rate of 20°/h. Evolution of carbonization products is different for the bulk and powdered samples. The observed differences are caused by secondary reactions of water with surrounding polymer producing H2 and CO2, which occur in the bulk samples. Flexural strength and modulus show minima at about 550°C which are related to maximum rate of H2 and CO2 evolution produced by the secondary reactions of water with the polymer structure.