Constructing Sandwich-Architectured Poly(l-lactide)/High-Melting-Point Poly(l-lactide) Nonwoven Fabrics: Toward Heat-Resistant Poly(l-lactide) Barrier Biocomposites with Full Biodegradability.

Heat-resistant poly(l-lactide) (PLLA) barrier biocomposites with full biodegradability were realized through the construction of locally oriented and compact transcrystallinity supernetworks in the network of high-melting-point poly(l-lactide) (hPLLA) nonwoven fabrics composed of high-efficiency nucleating hPLLA fiber through design of two types of sandwich architectures for PLLA/hPLLA nonwoven fabrics, where single or double hPLLA nonwoven fabrics were introduced at the core or two sides of PLLA matrix film, respectively. The hPLLA fiber induced dense and oriented PLLA transcrystallinity in networks of hPLLA nonwoven fabrics and impermeable crystalline layers were formed with well-interlinked lamellae, which served as impermeable barriers to oxygen and water vapor molecules. Moreover, hPLLA nonwoven fabrics involving the compact transcrystallinity behaved as framework to support the PLLA matrix and resist the thermal deformation. The sandwich-architectured PLLA with double hPLLA nonwoven fabrics exhibited better barrier properties and heat resistance than that with single hPLLA nonwoven fabrics. Compared with neat PLLA, the oxygen permeability coefficient and water permeability coefficient of PLLA/double hPLLA nonwoven fabric biocomposites significantly decreased by 61.7% and 58.7%, and the storage modulus increased by a factor of 160 at 80 °C. This work provides a novel method to fabricate heat-resistant PLLA barrier film with full biodegradability for packaging application.