Stereocomplex crystallites induce simultaneous enhancement in impact toughness and heat resistance of injection-molded polylactide/polyurethane blends

Abstract

Despite its attractiveness as an "green" substitute for conventional petroleum-based polymers, the current application of plant-derived biodegradable poly(L-lactide) (PLLA) in many fields has been greatly limited by its inherent brittleness and poor heat resistance. Herein, taking thermoplastic polyurethane (TPU) toughened PLLA as an example, we report a facile and promising strategy for the fabrication of supertoughened and heat-resistant PLLA/elastomer blends by incorporating small amounts (e.g., 2.5 wt%) of poly(D-lactide) (PDLA) into the blends through melt-blending and subsequent injection molding. The incorporated PDLA chains can readily collaborate with neighboring PLLA matrix chains during the meltblending process to co-crystallize into stereocomplex (sc) crystallites in the PLLA matrix of the blend melts. Thus, these sc crystallites can behave as a highly efficient nucleating agent to significantly accelerate matrix crystallization, allowing for the preparation of PLLA blends with a highly crystallized PLLA matrix using practical injection molding. The highly crystallized matrix can provide the PLLA/TPU blends with dramatically improved impact toughness and heat resistance as compared with the amorphous one. Meanwhile, the role of these sc crystallites as a rheology modifier to induce the unexpected morphological change from the dispersed TPU phase from the sea-island structure to the unique network-like structure with a much higher toughening efficiency is also observed.

Super-Toughed PLA Blown Film with Enhanced Gas Barrier Property Available for Packaging and Agricultural Applications

“…The interfacial interaction between polymers can be evaluated by the variation of rheological parameters [17], such as storage modulus (G′), loss modulus (G″), complex viscosity, and relaxation time. The SC crystallites’ melt temperature is almost 50 °C higher than PLLA, which can serve as an efficient rheological modifier to improve the elastic response and viscosity of PLLA melt owing to the filler effect and crosslinking effect of the SC crystallite network [18,19].…”

Achieving a low electrical percolation threshold and superior mechanical performance in poly(l-lactide)/thermoplastic polyurethane/carbon nanotubes composites via tailoring phase morphology with the aid of stereocomplex crystallites

“…[44][45][46][47][48][49][50] Moreover, super-toughened and heat-resistant PLLA/elastomer blends can be prepared by using small amounts of SC crystallites as a highly efficient nucleating agent to signicantly accelerate PLLA matrix crystallization. 51 Very recently, we further conrm that the construction of SC crystallites in the PLLA/elastomer blends is an elegant strategy for the morphological transition of the minor elastomer phase from the common well-dispersed droplets to the unique continuous structure. 52 Encouraged by this inspiring result, it is natural to think what would happen when CNTs are selectively localized in the elastomer phase of these blends.…”

The role of cold crystallization of homochiral crystallites in the superb heat resistant poly(lactic acid)

“…The specific structure offers SC many unique properties such as high melting temperature, efficient nucleation ability to homocrystallization. SC is a promising strategy to improve the crystallization rate of PLA . When the asymmetric blend of PLLA and PDLA is subjected to heat over 185°C, all the homocrystals are in the molten state, while the SC crytallites stay unmelted because of its high melting temperature.…”