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Recently, stereocomplex-type polylactide (SC-PLA) has generated growing interest because the unique SC crystals can provide drastic improvement in the heat/chemical resistances and durability of bio-derived and biodegradable PLA, exhibiting great potential to compete with some petroleum-derived engineering plastics in diverse applications. However, SC-PLA suffers from poor melt memory effect as well as significant thermal degradation after being completely melted at temperatures above 250 °C, which make it challenging to converse SC-PLA into useful products using versatile melt-processing technologies. With these challenges in mind, in this work, we propose a facile and practical strategy to fabricate SC-PLA products with exceptional thermomechanical properties through low-temperature melt-processing of SC-PLA powder with a bimodal melting temperature distribution. The results show that the melting temperature (T m) bimodality makes SC-PLA powder able to be easily injection molded at a relatively low temperature of 210 °C (between the two T m s) due to the selective melting of the low- T m SC-PLA component (SC- l PLA, ca. 20–40 wt%), indicating a good melt-processability. Meanwhile, the high- T m SC-PLA (SC- h PLA) component can directly deliver its desirable properties to the injection molded SC-PLA products. More importantly, during the injection molding process, the unmelted SC- h PLA particles can also induce the exclusive SC crystallization of the SC- l PLA melt as nucleating agent and greatly amplify the shear stress imposed on the melt as "rigid particles", finally generating numerous oriented SC structure in the SC- l PLA. Consequently, the injection molded SC- h PLA/SC- l PLA products exhibit impressively high tensile strength (74.3 MPa) and Vicat softening temperature (211.6 °C). Overall, this work presents an effective guidance for achieving desirable melt-processability of SC-PLA without sacrificing its thermomechanical properties and provides an industrial processing route towards high-performance SC-PLA products. Image 106841 • SC-PLA products were fabricated by low-temperature melt-processing of bimodal SC-PLA powder. • The melting temperature bimodality plays a key role in achieving balanced melt-processability and product performance. • The SC- l PLA component can provide the powder with good low-temperature melt-processability. • The SC- h PLA component can endow the melt-processed products with exceptional thermomechanical performance. • SC- h PLA induced exclusive SC formation and crystal orientation can also contribute to the enhanced performance. [ABSTRACT FROM AUTHOR]

Abstract: Stereocomplex (SC) crystallization between poly( l‐lactide) (PLLA) and poly( d‐lactide) (PDLA) exhibits tremendous potential to improve the properties of polylactide (PLA), but the practical processing of SC‐type PLA (SC‐PLA) is significantly hindered by the insufficient melt stability and serious degradation after complete melting of SC crystallites over 240 °C. In a previous work, powder metallurgy inspired low‐temperature (180–210 °C) compression sintering is proposed to fabricate SC‐PLA products from its nascent powder. However, its industrial application is still challenging mainly due to the low production efficiency (half an hour is required) as well as the weak ability to fabricate products with complex shapes. In this work, an effort to rapidly fabricate complex‐shaped SC‐PLA products using low‐temperature injection molding technology is reported, where SC‐PLA nascent powder is partially melted. To ensure appropriate powder flowability, small amounts of glyceryl monostearate are incorporated as a lubricant. The results show that, both the self‐nucleation and flow‐induced nucleation effects facilitate the SC crystallization across the interfaces between adjacent unmelted powder particles, which considerably shortens the sintering cycle to about 2 min. In this way, complex‐shaped SC‐PLA products (such as gears) with superb performance are successfully fabricated by injection molding for the first time. [ABSTRACT FROM AUTHOR]