The performance of biodegradable tung oil coatings

• The tung oil coating cured faster with more catalyst.
• An induction and acceleration period existed in the autoxidization of catalyzed tung oil.
• The microorganism attacked the surfaces either uniformly or at specific weak points.
• The weak point on the crosslinked chain could locate at carbonyl-containing groups.

Using immersion tests, viscosity measurements, FTIR and SEM, as well as biodegradation tests, biodegradable tung oil coatings were investigated. Results showed that the curing times for different formulae decreased as the amount of catalyst increased. During the curing process, there was an initial induction period where the viscosity remained more or less the same, and after a certain time, a sharp increase in viscosity was observed. The steady viscosity increased with time, revealing a continuous autoxidation process. Microorganisms in the soil attacked the surfaces of the tung oil films either uniformly on the whole plate or at specific weak points, leading to decreased volume, blurring of the small humps as well as holes. The weak point on the crosslinked chain was located at the carbonyl-containing groups, where chemical biodegradation occurred more easily and faster.