Employing a novel bioelastomer to toughen polylactide

Biodegradable, biocompatible polylactide (PLA) synthesized from renewable resources has attracted extensive interests over the past decades and holds great potential to replace many petroleum-derived plastics. With no loss of biodegradability and biocompatibility, we highly toughened PLA using a novel bioelastomer (BE)–synthesized from biomass diols and diacids. Although PLA and BE are immiscible, BE particles of ∼1 μm in diameter are uniformly dispersed in the matrix, and this indicates some compatibility between PLA and BE. BE significantly increased the cold crystallization ability of PLA, which was valuable for practical processing and performance. SEM micrographs of fracture surface showed a brittle-to-ductile transition owing to addition of BE. At 11.5 vol%, notched Izod impact strength improved from 2.4 to 10.3 kJ/m2, 330% increment; the increase is superior to previous toughening effect by using petroleum-based tougheners

Interfacial stereocomplexation in heterogeneous polymer powder formulations for reinforcing (laser) sintered welds

To understand the relation of molecular design of powder formulations in the realization of effective stress transfer at sintered polymer \u2013 polymer interfaces by the concept of interfacial stereocomplex crystallization in a broad temperature range, the effect of temperature and molar mass ratio are studied in heterogeneous poly(lactide) melt-states. Whereas the stereocomplex crystallization rate is dictated by supercooling and relative viscosities, the length-scales depend on the formation of crystalline stereocomplex domains connected via amorphous regions resulting in network formation, gelation. Upon gelation, further diffusion is impeded, which is supported by rheometry, DSC and FTIR imaging. When the initial relative viscosity between the PLA fractions is low, the time to reach critical network density is high. On the contrary, the length-scales of stereocomplex crystallization and ultimate mechanical stiffening are strongly influenced by the chosen temperature and molar mass ratio of the PLA fractions. Occurrence of interfacial stereocomplex crystallization under the non-isothermal conditions of selective laser sintering is validated. This fundamental understanding on the time- and length-scales of interfacial diffusion, successive stereocomplex crystallization, and nucleation of homocrystals upon further cooling, assists in the technical assurance of mechanically reinforced polymer-polymer interfaces \u2013 not only in sintered but in additively manufactured polymeric constructs in general