Adhesion and Hardness Evaluation of Modified Silicone-Dammar as Natural Coating Materials

Problem statement: Dammar is a natural resin that used anciently in varnish production. The use of dammar natural resin in coating is limited by undesirable properties for application in coating where it is considered very brittle. Due to dammar's brittle nature, an aged dammar coating can be easily scratched or abraded. Approach: Dammar natural resin could be modified into Silicone-Dammar by using a solvent in order to improve the coating’s mechanical properties. The modified Silicone-Dammar (SD) was coated on aluminum q-panel and adhesion was evaluated using cross hatch test, impact test and pull off test, while the hardness of coating was investigated by nano-indentation test. Results: Results from cross hatch test, impact test and pull off test show that coating material with 15% wt. of dammar (SD15) was the optimum composition which exhibits good adhesion of modified Silicone-Dammar to the metal substrate. SD15 also could be considered as a soft and flexible polymer coating with hardness value of 1.624 GPa after undergoing the nano-indentation test. Conclusion: A modified Silicone-Dammar coating system with varied compositions of dammar has been prepared and adhesion and hardness have been evaluated. It is found that 15% wt. of dammar in the coating material (SD15) exhibits good adhesion to aluminum substrate and soft and flexible in nature.