Toughness improvement was investigated for marine biodegradable polymers. As the matrix polymers, polybutylene succinate (PBS), polylactic acid (PLA) and polyglycolic acid (PGA) were used. While PBS is expected to exhibit marine biodegradability through the addition of enzymes, PLA and PGA are inherently marine biodegradable. Polycaprolactone-graft-polyrotaxane (GPR) was melt-mixed into the matrix polymer as a modifier. GPR is recognized for its toughness-enhancing effect on various polymers and possesses marine biodegradability. Ti catalysts to promote the ester exchange reaction between the PCL grafted on the GPR and the matrix polymer were also examined. Tensile testing of the film was conducted, and toughness was evaluated from stress-strain curve as an indicator of ductility. The results showed that toughness improves with the addition of GPR and Ti catalysts. The longest relaxation time, τ1, increased with the addition of GPR, and it further increased with the addition of the Ti catalyst. It is presumed that grafting occurred between the PCL molecules of GPR and the matrix polymer molecules, allowing the GPR to more effectively enhance toughness.
