Unique Morphology of Polylactide/Poly(ε-Caprolactone) Blends Extruded by Eccentric Rotor Extruder

In this work, PLA/PCL blends were extruded by either eccentric rotor extruder (ERE) based on extensional flow or twin-screw extruder (TSE) based on shear flow. The morphologies of PLA/PCL blends were investigated. The results showed that PLA/PCL blends showed co-continuous structure with PCL content varying from 20 to 50 wt% when the blends were extruded by ERE, while only 50 wt% PCL blends showed co-continuous structure when extruded by TSE. Furthermore, ERE provided better mixing properties, i.e., better dispersion of minor phase with smaller droplet sizes, promoting the formation of co-continuous structures with lower amounts of minor component. ERE also provided less polymer chain scission than TSE, implying better comprehensive properties of extruded polymers. DSC curves of PLA/PCL blends showed that the cold crystallization temperature (T-cc) of PLA shifted to lower temperature and the crystallinities of PLA increased when the blends were extruded by ERE. Implication of this work is that extensional flow is a more powerful method than shear flow in processing immiscible blends, which has high potential for compounding biobased and biodegradable polymer blends for enhanced properties.

Automated summary

In this study, PLA/PCL blends were extruded using eccentric rotor extruder (ERE) and twin-screw extruder (TSE), and their morphologies and properties were investigated. The results showed that ERE provided better dispersion and compatibility, as well as less polymer chain scission. Additionally, ERE promoted the crystallinity of PLA.