The Effect of p-Toluenesulfonic Acid and Phosphoric Acid (V) Content on the Heat Resistance and Thermal Properties of Phenol Resin and Phenol-Carbon Composite

This work presents the results of research on the influence of the amount of p-toluenesulfonic acid and phosphoric acid (V) added to the phenol-formaldehyde resin (pH 7.3–7.8) on its thermal properties and on the phenol-formaldehyde-carbon composite produced on its basis. This material undergoes pyrolysis under high temperature. The addition of a catalyst to the phenol-formaldehyde resin affects its curing rate and degree of cross-linking, but how it affects the thermal properties of the resin depending on the temperature is the subject of this work. This article presents the results of thermal tests for phenol-formaldehyde resin and phenol-formaldehyde-carbon composite. It was examined how the content of the catalyst used during the production process affects the individual thermal parameters of the mentioned materials. The results include experimental tests of thermal diffusivity with uncertainty (±3%), specific heat capacity (±2.5%), thermal expansion with resolution 2 nm analyzed in the temperature range −40–115 °C and thermogravimetric TG/DTA analysis with resolution 0.03 µg in the temperature range from room temperature (RT = 23 °C) to 550 °C. Individual thermal tests showed changes in the thermal properties caused by changes in the catalyst content of the tested materials and the influence of the addition of carbon fibers on the properties of the composite compared to the pure phenol-formaldehyde resin. It was found that there is a certain maximum level of catalyst weight fraction at which the greatest decrease in thermal diffusivity occurs. In the case of phenolic-formaldehyde-carbon composite at −40 °C, an increase in catalyst weight fraction from 2 to 4 wt% caused a decrease in thermal diffusivity by 18.2%, and for phenol-formaldehyde resin, it was 2.8% with an increase in catalyst fraction from 4 to 10 wt%.