Soil and microbial degradation study of poly(ε-caprolactone)-poly(vinyl butyral) blends

Biodegradation of blends of poly(epsilon-caprolactone) [PCL] with poly(vinyl butyral) [PVB] was studied in the soil and by bacterial strains of Bacillus subtilis and Escherichia Coli isolated from the soil. Miscibility of the blends was also analyzed using FT-IR and optical microscopy at room temperature. Biodegradation of the blends was followed by weight loss, visual observations and scanning electron microscopy [SEM]. Blends with low polyester concentration, i.e., 30 wt% PCL and less, were clear and transparent and no spherulite formation was observed. Above 30 wt% PCL spherulites appeared, the size of which increased with increasing PCL concentration. Infra-red studies of the blends with less than 30 wt% PCL showed that only the amorphous phase of PCL was present. Above 30 wt% PCL indicated the presence of both crystalline and blended PCL. The second derivative of the carbonyl peak of PCL also supported the presence of two phases in blends with more than 30 wt% PCL and only one peak for blends with 30 wt% or less PCL. Weight loss was observed in all the blends. PCL rich blends showed more degradation, which was faster in the natural environment than in the laboratory. Physical appearance and microscopic examination showed the films deteriorated in soil. Blends in the Bacillus subtilis strain showed more degradation as compared to the E. Coli. strain.