Study on the mechanical property and the biodegradability of starch-PCL blend

Abstract

In the present study, the blend of a gelatinized starch and PCL was prepared by using various kinds of compatibilizer and their mechanical properties were investigated. The mechanical properties of the starch/PCL blends by using various PEGs that have a different molecular weight were investigated. From the change of toughness of the blends with the PEG molecular weight, it was found that the blend containing PEG of molecular weight 3400 shows a highest tensile toughness. It was also found from the SEM images that the blend containing PEG of molecular weight 3400 has the smallest domain size of the starch dispersion phases. The interactions between starch and PEG, between PCL and PEG in the blend were studied by using the DSC and FT-IR techniques. Only the PEG which has a proper molecular weight could act as an effective compatibilizer for the starch/PCL blends. The poly(acrylic acid)-g-polycarprolactone(PAA-g-PCL) graft copolymer was synthesized and the starch/PCL blends compatibilized with PAA-g-PCL were also prepared. The mechanical properties of the starch/PCL blends compatibilized with various PAA-g-PCLs that have different graft degree and graft length were investigated. As the graft degree of the PAA-g-PCLs that have the same graft length increased, the modulus and the strength of the blends decreased. However, the elongation at break and the tensile toughness of the blends showed a maximum at a certain graft degree (10.8mol%) due to the better compatibilizing effect compared to the low(3.9mol%) and the high(23.4mol%) graft degree of PAA-g-PCL. It was also found that the modulus and the strength of the blends increased with the increase of graft length of the PAA-g-PCLs that have the same graft degree(11mol%). However, the blend compatibilized with the short graft length(M.W. of PCL graft : 530) exhibited the highest value of the elongation at break and the tensile toughness. This result is attributed to the self-crystallization of PAA-g-PCL in the ble...