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Synergistic Effect of Multi-Arm Architecture and Molecular Weight on Crystallization and degradation Behavior of Star-Shaped Poly(Lactic Acid)

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Chinese Journal of Polymer Science 2024年第12期42卷 1948-1956,I0009页

作者： Nan Tian Yi-Qing Li Hong-Yi Gan Zhen-Bo Ning Ni Jiang Zhi-Hua Gan State Key Laboratory of Organic-inorganic Composites Beijing Laboratory of BiomaterialsCollege of Life Science and TechnologyBeijing University of Chemical TechnologyBeijing100029China Institute of Material Sinopec Beijing Research Institute of Chemical IndustryBeijing100013China

Star-shaped poly(lactic acid)s(PLAs)with two to five arms were synthesized by ring opening polymerization using tin(II)2-ethylhexanoate as catalyst and polyols as *** effects of molecular weight together with multi-arm architecture on crystallization behavior,spherulite morphology and alkaline degradation behavior of star-shaped PLAs have been *** results indicate that the multi-arm architecture interfered with spherulite growth,but promoted nucleation and alkaline degradation of star-shaped ***,with the increase of molecular weight(M_(n)),the crystallization rate first increased and then decreased,while the alkaline degradation rate was the *** characteristic crystallization and alkaline degradation behavior of star-shaped PLAs were discussed based on the competition between segmental mobility and central core confinement.

关键词： Star-shaped poly(lactic acid) Crystallization Spherulite morphology alkaline degradation

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Analysis on degradation behaviors of sisal fibers at various pH conditions

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Journal of Southeast University(English Edition) 2022年第3期38卷 278-283页

作者： Zhao Li Li Shujin Song Yang Zhang Yamei School of Materials Science and Engineering Southeast UniversityNanjing 211189China School of Civil Engineering and Architecture Changzhou Institute of TechnologyChangzhou 213032China

The degradation behaviors(mass loss,tensile strength,crystallinity index,and microstructure)of sisal fibers immersed in sodium hydroxide solution with pH of 13.6,12.9,and 11.9 were investigated via X-ray diffraction and scanning electron microscopy.A three-stage degradation process of natural fibers in an alkaline environment was *** results showed that the sisal fibers exhibited a sharp mass loss over the first 7 d of degradation under all pH conditions,attributable to the rapid hydrolysis of lignin and hemicellulose at the fiber *** sisal fibers degraded at pH 12.9 and 13.6 over 1 month exhibited significantly lower tensile strengths(181 and 195 MPa,respectively)than the original fibers(234 MPa)because of the loosely bound structure of the component microfibrils caused by the hydrolysis of the linking lignin and *** 6-month degradation,stripped microfibrils occurred in the fibers,resulting in substantial degradation in tensile *** sisal fibers degraded at pH 11.9 largely maintained their integrity and tensile strength,even after 6 months,indicating that reducing the environment pH can effectively mitigate the degradation.

关键词： sisal fibers cement composites alkaline degradation microstructure tensile strength

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