Development and characterization of self-healing car paint using chitosan

Thesis Abstract

Car surfaces are vulnerable to scratches from environmental conditions, thereby prompting car users to visit car workshop for re-spray. This process does not usually bring permanent solution to scratches on car surfaces since they are often re-spray with non-self-healing paint. The aim of this work was to develop self-healing car paint. In doing this, response surface methodology (RSM) was used to obtain an optimum paint formulation which was then improved into a self-healing car paint by incorporating chitosan into the formulation, sprayed on substrates, allowed to dry, scratched with a pin, exposed with UV light from the sun and then investigated for self-healing using scanning electron microscope (SEM).

The model developed for drying time and coverage responses using (ANOVA) in the RSM study were significant as their respective “Prob > F” values were less than 0.0500 with R2 values 0.8693 and 0.9204 respectively. The “lack of fit” in both cases were not significant which is desirable in statistical analysis of this nature. Physico-chemical analysis (viscosity, density and pH) were done on the 20-runs of formulated paint where runs 1, 3, 7, 8 and 13 had the best density values of 0.956 g/cm3, 0.977g/cm3, 0.875 g/cm3, 0.896 g/cm3 and 0.944 g/cm3respectively as compared to other runs. Runs 1, 3, 7, 8 and 13 viscosity values fall within range of “30±5 cp”,(ASTM, 2009; PAN, 2013) standard specification for car paint. The pH values of the twenty runs were in the range of 6.6 to 6.9.

The physico-chemical test performance of runs 1, 3, 7, 8 and 13 was a criteria for their selection to undergophysico-mechanical test, in which run 8 among the other runs selected had the optimum performance in terms of gloss, film thickness, cross-scratch, punch, chemical resistance, heat resistance and colour stability tests as its results agreed closely to ASTM/PAN car paint standard specifications.The SEM analysis done on the coated substrates showed that chitosan has self-healing effect.