ASSESSMENT OF PHYSICO-CHEMICAL PARAMETERS AND MICROBIAL STABILITY OF WATER-BASED PAINTS

Justification and Aim of Study: Biodeterioration of emulsion paints is a negative outcome of microbial metabolic process with serious economic and health implications. Therefore it is justifiable to examine the physico-chemical parameters and microbial stability of emulsion paints with the view to improving the durability of the products, hence this study.

Methodology: Four paint samples of different make were obtained from retail paint shops and analyzed for the presence of microbial contaminants using standard microbiological techniques. The physico-chemical parameters such as pH, viscosity and specific gravity were also evaluated. Pure cultures of the isolates were identified and characterized using conventional cultural, morphological and biochemical characteristics, and the API 20 NE and 1D 32E test systems.

Results: The results showed that all the samples were contaminated with bacteria and moulds. There were variations in the result of physico-chemical parameters studied such as reduction in the values of PH and viscosity, with increase in the number of acid producing strains of microbial contaminants. Some of the microorganisms isolated and their frequency of occurrence were Aspergillus niger (10.87%), Pseudomonas aeruginosa (8.70%), Alternaria alternate (2.17%), Penicillium citrinum (6.52%), Mucor rouxii (6.52%), Rhizopus arrhinus (6.52%)), Flavobacterium breve (4.35%), Bacillus polymyxa (4.35), Lactobacillus gasseri (4.35%), Alcaligenes eutrophus (4.35%) and Alternaria alternate (2.17%). There was significant difference (P = 0.05) between the number of fungi and bacteria isolated from the paint samples.

Conclusion: The presence of these organisms in water-based paint suggests that emulsion paint offers favourable conditions for microbial growth and are therefore very susceptible to biodeterioration.

Recommendation: Unfavorable conditions for microbial growth such as reduced moisture level, use of more potent biocides and other antimicrobial preservatives should be adopted to enhance microbial stability and prolong the shelf life of emulsion paints.