Quantitative Investigation on Structural Evolution of Co-continuous Phase under Shear Flow

Components of co-continuous phase can form an interpenetrating network structure, which has great potential to synergistically improve the mechanical properties of the blends, and to impart the functional blends superior electrical conductivity and permeability. In this work, the effects of shear rates (50-5000 s(-1)) at different temperatures on the phase morphology, phase size and lamellar crystallites of biodegradable co-continuous polybutylene terephthalate (PBAT)/polybutylene succinate (PBS) blend are quantitatively investigated. The results show that the above features of the PBAT/PBS have a strong dependence on the shear flow and thermal field. The co-continuous phase of the blend is well maintained at 130 degrees C. Interestingly, this phase structure transforms into a sea-island structure at 160 degrees C, which gradually recovers to a co-continuous phase when the shear rate increases from 1000 s(-1) to 5000 s(-1). The phase size decreases with the increase of shear rate both at 130 degrees C and 160 degrees C due to the refinement and deformation of phase structures caused by strong shear stress. Unexpectedly, a unique phenomenon is observed that the shear-induced lamellar crystallites are oriented perpendicular to shear direction in the range of 500-5000 s(-1) at 130 degrees C, while the orientation of lamellar crystallites at 160 degrees C is along the shear direction within the whole range of shear rates. The degree of orientation for the PBAT/PBS blend crystals increases first and then decreases at both temperatures above. In addition, the range of shear rate has reached the level in the industrial processing. Therefore, this work has important guiding significance for the regulation of the co-continuous phase structure and the performance for the blend in the practical processing.

Automated summary

This study quantitatively investigated the effects of different shear rates at various temperatures on the phase morphology and crystalline structure of PBAT/PBS blend. The findings indicate that the maintenance of the co-continuous phase is influenced by temperature and shear flow, while increasing shear rate leads to a decrease in phase size and changes in crystal orientation.