木质纤维-聚己内酯-聚乳酸“核-壳-壳”增韧聚乳酸复合材料及增韧机制研究

This study aims to improve the compatibility and toughness of wood fiber/poly(lactic acid)(WF/PLA)composites by employing a surface-initiated ring-opening polymerization(SI-ROP)approach.The method involves fabricating a"core-shell-shell"structure with wood fibers at the core,a poly(caprolactone)(PCL)rubber shell layer,and an outer poly(lactic acid)(PLA)shell layer.The WF-rD-PLA/PLA composites were fabricated via melt blending and extrusion.The chemical structure,crystalline properties,morphology,thermal and thermal degradation properties,tensile properties and impact strength were comprehensively analyzed by Fourier transform infrared spectroscopy(FTIR),X-ray diffractometer(XRD),scanning electron microscopy(SEM),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),universal mechanical tester and pendulum impact tester.The results showed that:(1)The absorption peaks corresponding to-C-H and C=O were stronger after modification,confirming the successful grafting of PCL flexible chains and PLA onto the WF surfaces via the SI-ROP reaction.(2)XRD results showed a significant decrease in the crystallinity of the modified wood fibers,suggesting that the polymer chain introduction disrupted the regularity of the wood fiber structure.Conversely,the crystallinity of the composite increased significantly,indicating improved interfacial adhesion and mobility.(3)The SEM of the modified composite showed a stretching and ductility morphology,suggesting the enhanced toughness of the composite.(4)Mechanical testing reveled that the tensile toughness of the alkali-treated WF-rD-PLA/PLA composites increased by 335.9%,albeit with a slight reduction in its strength.(5)The modified composite did not exhibit distinct relaxation peaks within the glass transition temperature(Tg)range,and the Tg increased,suggesting a reduction in the mobility of the PLA chains and an enhancement of the interfacial compatibility of the composites.The TGA data showed that the thermal stability of the modified composites was decreased,which was attributed to the formation of low molecular weight PLA chains on the WF surfaces.The SI-ROP technique effectively enhances the compatibility and mechanical properties of WF/PLA composites,offering a promising approach for the development of high-performance bio-based materials.