Effect of cellulose acetate butyrate on flow-induced crystallization of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

In the present study, we investigated the crystallization behaviors of blends comprising poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) (PHBHHx) and cellulose acetate butyrate (CAB) with/without an applied shear history. The blends had phase-separated structures, although some of the CAB chains dissolved in the PHBHHx in the molten state. Owing to CAB dissolution, the linear growth rate of the radii of the PHBHHx spherulites decreased at the point of isothermal crystallization, and crystallization occurred at low temperatures during cooling. The blend films had low crystallinities owing to the reduced crystallization rate. After shear history, however, crystallization occurred at high temperatures when the CAB was added; i.e., the flow-induced crystallization of PHBHHx was enhanced. The dispersed CAB droplets acted as rigid particles because CAB has a high glass transition temperature. This situation accelerates the actual shear rate in the PHBHHx located between the CAB particles, leading to flow-induced crystallization. This technique promotes the industrial application of PHBHHx because the processing window is broadened by accelerating the crystallization rate during flow field using a biomass-based modifier.