| Polylactide (PLA), a biodegradable thermoplastic derived from renewable resources, stands out as a substitute to petroleum-based plastics. However, PLA have poor foaming properties due to their lower melt strength, weak CO2absorption capability. In this work, the epoxy-base chain extender (CE), melt enhancer, poly (ionic liquid)s (PIL) and PDMS have been used to modify PLA by melt blending for the first time. The main research contents and conclusions are illustrated as follow:(1) PLA was branched using styrene-glycidyl methacrylate copolymer through melt compounding. Supercritical carbon dioxide (Sc-CO2) was used as physical foaming agent. The GPC result showed that the molecular weight was elevated one order of magnitude. The rheology data showed that the complex viscosity and enlongational viscosity improved significantly with the incorporation of chain extender. Compared to neat PLA foam, the chain branched PLA exhibited decreased cell size as well as increased cell density due to the improved viscous properties.(2) The compatibility of PIL and PLA was successfully improved by copolymerization of IL and LMA. The isothermal crystallization kinetics of PLA/PIL composites was investigated by DSC. The Avrami method was used to describe the isothermal crystallization behavior. The crystallization process was accelerated by PIL, because of its outstanding nucleation effect.(3) The thermostability of PLA was enhanced by melt enhancer. While the samples presented the same rheological properties as blank sample, better foaming properties was observed. The addition of PIL-ran-PLMA also reduced the cell size and increased cell density. Poor foaming properties were observed when PDMS was added in. |
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