PLA的酸性降解及其机理分析
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摘要
目的研究PLA在酸性条件下降解及其机理。方法通过在酸性水溶液中降解不同时间,得到一系列不同相对分子质量的PLA,利用黏度法、凝胶色谱以及红外光谱对PLA的降解机理进行研究。结果 PLA的数均分子量随降解时间的增加逐渐减小,失重率和降解率逐渐升高,在降解23 d后,产物的数均分子量从4050降至2490,失重率从9.9%升至75.1%,降解率从98.3%提高至99.0%。降解过程中,PLA的相对分子质量分布系数基本保持不变,一直维持在1.25左右。结论在降解过程中,酯键的断裂是PLA初步降解的主要方式,H+浓度的升高有利于催化酯键的断裂,加剧PLA降解。
Objective To study the acid degradation of PLA and to investigate its mechanism. Methods A series of PLA with different molecular weights were obtained after different degradation time in acidic aqueous solution, followed by viscometric determination, GPC and FTIR to analyze its degradation mechanism. Results The number-average molecular weight of PLA gradually decreased with the increasing degradation time, while the weight-loss rate and degradation rate gradually increased. After 23 d degradation, the number-average molecular weight of PLA diminished from 4050 to 2490,while the weight-loss rate and degradation rate accumulated from 9.9% and 98.3% to 75.1% and 99.0%, respectively. The molecular weight distribution coefficient remained stable at about 1.25 during the degradation. Conclusion The main initial degradation of PLA was the fracture of ester bond, which was accelerated by the concentration enhancement of H+. As a result, degradation of PLA was exacerbated.
Objective To study the acid degradation of PLA and to investigate its mechanism. Methods A series of PLA with different molecular weights were obtained after different degradation time in acidic aqueous solution, followed by viscometric determination, GPC and FTIR to analyze its degradation mechanism. Results The number-average molecular weight of PLA gradually decreased with the increasing degradation time, while the weight-loss rate and degradation rate gradually increased. After 23 d degradation, the number-average molecular weight of PLA diminished from 4050 to 2490,while the weight-loss rate and degradation rate accumulated from 9.9% and 98.3% to 75.1% and 99.0%, respectively. The molecular weight distribution coefficient remained stable at about 1.25 during the degradation. Conclusion The main initial degradation of PLA was the fracture of ester bond, which was accelerated by the concentration enhancement of H+. As a result, degradation of PLA was exacerbated.
引文
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[3]YUE Z,YOU Z,YANG Q,et al.Molecular Structure Matters:PEG-b-PLA Nanoparticles with Hydrophilicity and Deformability Demonstrate Their Advantages for High-performance Delivery of Anti-cancer Drugs[J].J Mater Chem B,2013(1):3239—3247.
[4]HU Q,GAO X,GU G,et al.Glioma Therapy Using Tumor Homing and Penetrating Peptide-functionalized PEG-PLA Nanoparticles Loaded with Paclitaxel[J].Biomaterials,2013,34:5640—5650.
[5]张晓惠,黎厚斌.PLA改性及其在包装领域的应用[J].包装工程,2008,29(8):237—239.ZHANG Xiao-hui,LI Hou-bin.Modification of Polylactic Acid and Its Application in Packaging[J].Packaging Engineering,2008,29(8):237—239.
[6]GARCIA G,TABOADA R,LOPEZ G,et al.Active Packaging of Cardboard to Extend the Shelf Life of Tomatoes[J].Food Bioprocess Technol,2013(6):754—761.
[7]JAMSHIDIAN M,TEHRANY E A,DESOBRY S,et al.Antioxidants Release from Solvent-cast PLA Film:Investigation of PLA Antioxidant-active Packaging[J].Food Bioprocess Technol,2013(6):1450—1463.
[8]ARRIETA M P,LOPEZ J,FERRANDIZ S,et al.Characterization of PLA-limonene Blends for Food Packaging Applications[J].Polymer Testing,2013,32:760—768.
[9]BANG G,KIM S W.Biodegradable Poly(Lactic Acid)-based Hybrid Coating Materials for Food Packaging Films with Gas Barrier Properties[J].Journal of Industrial and Engineering Chemistry,2012,18:1063—1068.
[10]瞿丽曼.PLA在国内外包装应用中的发展趋势[J].化工新型材料,2007,35(3):100—102.QU Li-man.Development Trend of Polylactic Acid in Packaging Applications[J].New Chemical Materials,2007,35(3):100—102.
[11]董奇伟.PLA降解性能研究进展[J].塑料制造,2011(3):66—69.DONG Qi-wei.Research Progress of Degradation of PLA[J].Plastics Manufacture,2011(3):66—69.
[12]麦杭珍,赵耀明,陈军武.PLA的成型加工及其降解性能[J].塑料工业,2000,28(5):28—30.MAI Hang-zhen,ZHAO Yao-ming,CHEN Jun-wu.Forming Process of Poly(L-lactic Acid)and Its Biodegradability[J].China Plastic Industry,2000,28(5):28—30.
[13]孙媚华,陈迁,宋光泉.PLA的降解研究[J].化工新型材料,2013,41(1):140—142.SUN Mei-hua,CHEN Qian,SONG Guang-quan.Research of Degradation of Polylactic Acid[J].2013,41(1):140—142.
[14]JONG DE S J,ARIAS E R,RIJKERS D T S,et al.New Insights into the Hydrolytic Degradation of Poly(Lacticacid):Participation of the Alcohol Terminus[J].Polymer,2001,42(7):2795—2802.
[15]TSUJI H,IKARASHI K.In Vitro Hydrolysis of Poly(L-lactide)Crystalline Residues as Extended-chain Crystallites:III.Effects of p H and Enzyme[J].Polymer Degradation and Stability,2004,85(1):647—656.
[16]冯舒勤,张乃文,任杰.PLA的热降解与稳定性[J].塑料,2011,40(1):59—62.FENG Shu-qin,ZHANG Nai-wen,REN Jie.Thermal Degradation and Stability of Poly Lactic Acid[J].Plastic,2011,40(1):59—62.