Green and renewable foaming poly(lactic acid) (PLA) represents one of the promising developments in PLA materials. This study is the first to use the lignin graft PLA copolymer (LG‐g‐PLA) to improve the foamability of PLA as a biobased nucleating agent. This agent was synthesized via ring‐opening polymerization of lignin and lactide. The effects of LG‐g‐PLA on cell nucleation induced by the crystallization, rheological behavior, and foamability of PLA were evaluated. Results indicated that LG‐g‐PLA can improve the crystallization rate and crystallinity of PLA, and play a significant nucleation role in the microcellular foam processing of PLA. LG‐g‐PLA improved the foam morphology of PLA, obtaining a reduced and uniform cell size as well as increased expansion ratio and cell density. With the addition of 3 wt% LG‐g‐PLA content, the PLA/LG‐g‐PLA foams increased the compressive strength 1.6 times than that of neat PLA foams. The improved foaming properties of PLA via a biobased nucleating agent show potential for the production and application of green biodegradable foams.
Microcellular foamed wood-plastic composites (WPCs) have shown good development prospects in environmentally-friendly composites. Herein, the foamed wood flour (WF)/polypropylene (PP) composites were fabricated by mold-opening injection molding using supercritical N 2 as a physical foaming agent. The effects of nano TiO 2 on the microcellular structure and mechanical properties of WF/PP composites were investigated, and the results show that nano TiO 2 accelerates the crystallization rate and reduces the crystallinity of PP, which is beneficial to the formation of foamed homogeneous systems and cell growth in the WF/PP composites. This is mainly due to heteronucleation effect of nano TiO 2 , resulting in the refinement of crystal. Molecular chain movement of PP is limited with the introduction of nano TiO 2 , resulting in increased the melt elasticity of WF/PP composites, thereby reducing cell coalescence and collapse. With the addition of 5 wt% nano TiO 2 , the cell density was increased by 393.8%, the cell size was reduced by 54.4%, and the cell size homogeneity was clearly improved. In addition, impact strength increased by 33.3%. The improved foamability of WF/PP composites using nano TiO 2 shows a great promise for the production and application of WPC foams, especially in automotive, packaging and building areas.cellulose and other wood products, composites, foams, porous materials, thermoplastics
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