聚乳酸的非等温结晶行为

doi:10.11944/j.issn.1000-0518.2016.07.150384

摘要/Abstract

摘要：

用差示扫描量热法(DSC)研究聚乳酸(PLA)从熔体及玻璃态为初始条件下的非等温结晶行为,采用Ozawa方程、Mo法、Khanna法和Kissinger法对结晶动力学参数进行计算处理。实验结果表明,这几种方法均适合处理PLA的非等温结晶过程,而Khanna法提出的结晶速率系数(CRC)能够方便地评价PLA相对结晶速率的大小。 PLA从玻璃态升温结晶比从熔体降温结晶容易得多,升温过程有利于晶核生成,而降温有利于晶体生长。升温结晶时,升温速率2.0 ℃/min时,结晶焓(ΔH_c)达到最大为27.1 J/g。从熔体等速降温过程中,随着冷却速率的降低ΔH_c单调增加,冷却速率为0.25 ℃/min时ΔH_c增加到28.3 J/g。在较低温度下从玻璃态结晶,主要表现为异相成核的二维生长方式。在较高的温度下从玻璃态升温结晶及从熔体冷却结晶时,以均相成核的三维生长方式结晶为主。与升温过程相比,冷却不利于晶核的生成,所以导致冷却过程总体ΔH_c偏低,扩散活化能偏大。

关键词: 聚乳酸, 非等温结晶, Ozawa方程, Khanna法, 聚合物熔体, 玻璃态

Abstract:

The non-isothermal crystallization behavior of polylactide(PLA) was investigated by differential scanning calorimetry(DSC), including heating from glass state and cooling from melted state for the PLA polymer. Crystallization kinetic parameters were calculated using Ozawa equation, Mo method, Khanna law and Kissinger method. These methods are all suitable for handling non-isothermal crystallization process of PLA.The crystallization rate coefficient(CRC) proposed by Khanna can easily evaluate the relative crystallization rate of PLA. In contrast to the cooling process from melted state, the heating process of PLA from glass state stimulates crystal nucleus generation, while cooling process is conducive to the growth of crystals. When the heating rate is at 2.0 ℃/min, crystallization enthalpy(ΔH_c) reaches the maximum of 27.1 J/g. When the crystallization starts from the melted state, ΔH_c increases with the decreasing cooling rate. The cooling rate is lowered to 0.25 ℃/min, and ΔH_c is increased to 28.3 J/g. At a lower temperature, the process of crystallization from the glass state, is mainly heterogeneous nucleation of two-dimensional crystal growth pattern. At higher temperature, crystallization from the glass state and melted polymer largely attributes to the homogeneous nucleation for three-dimensional growth pattern. Compared with the heating process, the cooling process is not conducive to the formation of crystal nucleus, so that in the cooling process ΔH_c is much lower, and the diffusion activation energy is a little higher than that in the heating process.

Key words: polylactide, non-isothermal crystallization, Ozawa equation, Khanna method, polymeric melted state, glass state

边新超, 冯立栋, 陈志明, 陈学思. 聚乳酸的非等温结晶行为[J]. 应用化学, 2016, 33(7): 766-773.

BIAN Xinchao, FENG Lidong, CHEN Zhiming, CHEN Xuesi. Non-Isothermal Crystallization Behavior of Polylactide[J]. Chinese Journal of Applied Chemistry, 2016, 33(7): 766-773.

参考文献

[1]	ZHUO Renxi,YIN Chao,WU Yingnan,et al.Synthesis and Degradation Behavior of Poly(DL-lactide) for Ophthalmic Application[J]. Chinese J Appl Chem,1997,14(2):102-104(in Chinese). 卓仁禧,尹超,吴颖楠,等. 聚乳酸眼科植入材料的制备及其降解性能[J]. 应用化学,1997,14(2):102-104.
[2]	Eling B,Gogolewski S,Pennings A J. Biodegradable Materials of Poly(L-lactic acid):1.Melt-Spun and Solution-Spun Fibres[J]. Polymer,1982,23(11):1587-1593.
[3]	Pennings J P,Dijkstra H,Pennings A J. Preparation and Properties of Absorbable Fibres from L-lactide Copolymers[J]. Polymer,1993,34(5):942-951.
[4]	LI Xiaohong,YUAN Minglong,HAO Jianyuan,et al.Progress and Prospects on the Academic Research and Industrial Application of Biodegradable Polymers[J]. Polym Bull,2008,52(8):109-122(in Chinese). 李孝红,袁明龙,郝建原,等. 生物降解聚合物的研究和产业化进展及展望[J]. 高分子通报,2008,52(8):109-122.
[5]	Garlotta D. A Literature Review of Poly(Lactic Acid)[J]. J Polym Environ,2001,9(2):63-84.
[6]	Tsuji H,Ikada Y. Properties and Morphologies of Poly(L-Lactide):1.Annealing Condition Effects on Properties and Morphologies of Poly(L-Lactide)[J]. Polymer,1995, 36(14):2709-2716.
[7]	Hernández-Sáncehz F,Molina-Mateo J, Romero Colomer F J, et al. Influence of Low-Temperature Nucleation on the Crystallization Process of Poly(L-lactide)[J]. Biomacromolecules,2005,6(6):3283-3290.
[8]	REN Jie,YANG Jun,REN Tianbin. Review of the Crystallization Behavior of Biodegradable PLA[J]. Polym Bull,2006,12:51-56(in Chinese). 任杰,杨军,任天斌. 生物可降解材料聚乳酸结晶行为研究进展[J]. 高分子通报,2006,12:51-56.
[9]	HE Yong,GAO Zhaofen,XIN Yan,et al.Crystallization Behavior of Poly(L-lactide)[J]. Chem Res Chinese Univ,2006,27(4):745-748(in Chinese). 何勇,高兆芬,辛燕,等. 左旋聚乳酸的结晶行为研究[J]. 高等学校化学学报,2006,27(4):745-748.
[10]	Pluta M,Galeski A. Crystalline and Supermolecular Structure of Poly Lactide in Relation to the Crystallization Method[J]. Appl Polym Sci,2002,86(6):1386-1395.
[11]	Li L B, Zhong Z Y, de Jeu W H, et al. Crystal Structure and Morphology of Poly(L-lactide-b-L-lactide) Diblock Copolymers[J]. Macromolecules,2004,37(23):8641-8646.
[12]	Abe H,Harigaya M,Kikkawa Y,et al.Crystal Growth and Solid-State Structure of Poly(lactide) Stereocopolymers[J]. Biomacromolecules,2005,6(1):457-467.
[13]	Huang J,Melissa S L,Runt J. Crystallization and Microstructure of Poly(L-lactide-co-meso-lactide) Copolymers[J]. Macromolecules,1998,31(8): 2593-2599.
[14]	LI Xungang. Influence of Two Nucleating Agent on Crystallization Properties of Poly(lactic acid)[J]. Polym Addit,2014,3:6-12(in Chinese). 李训刚. 两种成核剂对聚乳酸结晶性能的影响[J]. 聚合物与助剂,2014,3:6-12.
[15]	HUANG Weijiang,QIN Shuhao,ZHANG Kai,et al.Research Progress on Improvement of Polylactic Acid Crystallization Behavior by Nucleating Agent[J]. China Plast Ind,2013,41(1):12-17(in Chinese). 黄伟江,秦舒浩,张凯,等. 成核剂改善聚乳酸结晶行为的研究进展[J]. 塑料工业,2013,41(1):12-17.
[16]	XU Yang,SUN Zhidan,CHEN Xiaolang,et al.Effect of Crystallization Temperature on Crystal Modifications and Crystallization Morphology of Poly(L-lactic Acid)[J]. J Funct Mater,2012,43(16):2138-2141(in Chinese). 徐阳,孙志丹,陈晓浪,等. 结晶温度对左旋聚乳酸的晶体改性和晶体形貌的影响[J]. 功能材料,2012,43(16):2138-2141.
[17]	CHENG Haibo,CHEN Xuesi,XIAO Haihua,et al.Promotion of Crystallization in Linear Polylactide by Multiarm-polylactide[J]. Chinese J Appl Chem,2010,27(7):754-758(in Chinese). 程海波,陈学思,肖海华,等. 多臂聚乳酸对线型聚乳酸结晶的促进作用[J]. 应用化学,2010,27(7):754-758.
[18]	CHEN Xiaolang,XU Yang,SUN Zhidan,et al.Effect of Drawing Temperature on Structure and Properties of α'-Phase of Poly(lactic acid)[J]. Acta Chim Sin,2012,70(6):775-782(in Chinese). 陈晓浪,徐阳,孙志丹,等. 拉伸温度对α'-型聚乳酸结构与性能的影响[J]. 化学学报,2012,70(6):775-782.
[19]	Nijenhuis A J,Grijpma D W,Pennings A J. Lewis Acid-Catalyzed Polymerization of L-Lactide-Kinetics and Mechanism of the Bulk-Polymerization[J]. Macromolecules,1992,25(24):6419-6424.
[20]	FENG Lidong,GAO Zhantuan,BIAN Xinchao,et al.Isothermal Crystallization Kinetics of Polylactic Acid from Different Initial States[J]. J Funct Polym,2009,22(2):144-147(in Chinese). 冯立栋,高战团,边新超,等. 不同初始条件下聚乳酸的等温结晶动力学[J]. 功能高分子学报,2009,22(2):144-147.
[21]	TIAN Yi,QIAN Xin. Nonisothermal Crystallization Kinetics of Poly(Lactide) Plasticized with Poly(ethylene glycol)[J]. Polyester Ind,2007,20(2):15-18(in Chinese). 田怡,钱欣. 聚乙二醇增塑聚乳酸的非等温结晶动力学研究[J]. 聚酯工业,2007,20(2):15-18.
[22]	LIU Jieping,MO Zhishen,QI Yuchen,et al.Kinetics of Non-Isothermal Crystallization of PEO/PBHE Blends[J]. Acta Polym Sin,1993,1:1-6(in Chinese). 刘结平,莫志深,綦玉臣,等. 聚氧化乙烯(PEO)/聚双酚A羟基醚(PBHE)共混体系的非等温结晶动力学[J]. 高分子学报,1993,1:1-6.
[23]	MO Zhishen. A Method for the Non-Isothermal Crystallization Kinetics of Polymers[J]. Acta Polym Sin,2008,7:656-661(in Chinese). 莫志深. 一种研究聚合物非等温结晶动力学的方法[J]. 高分子学报,2008,7:656-661.