摘要
聚乳酸(PLA)作为可降解高分子材料已得到越来越多的人关注,并已在医用、包装领域得到了深入的应用,具有很好的发展前景。但由于PLA为脂肪族聚酯,易受热降解,其加工稳定性较差已经限制了PLA的使用。本文对PLA的加工热稳定性、挤出扩链增粘进行了研究。
主要研究了PLA在不同含水率、熔融温度条件下的分子量变化。实验结果表明：当PLA含有水分时加热,粘均分子量下降迅速,最终分子量与含水率、温度等有密切关系,当PLA充分烘干后加热时粘均分子量下降比较缓慢。对不同含水率PLA进行烘干确定了适合PLA的烘干温度和烘干时间,并用TGA、红外等分析测试,研究了PLA热降解的规律。
PLA在经过挤出机挤出后分子量也会下降,通过对挤出的PLA进行特性粘数、GPC等方法进行表征可知在挤出过程中PLA受机械剪切作用,随螺杆转速提高粘均分子量变小,分子量分布变窄。
选用改性二苯基甲烷二异氰酸酯(MDI)、异氰尿酸三缩水甘油酯(TGIC)为扩链剂,并用含有端羟基小分子与异佛尔酮二异氰酸酯(IPDI)反应制备扩链剂,研究了加入不同扩链剂、摩尔比时对PLA分子量的影响,并对比了加入小分子柔性链段后力学性能的变化。随扩链剂加入粘均分子量随之增加,熔融指数降低。加入小分子链段越长,断裂伸长率越大。相同分子量的聚酯链段比聚醚链段可更好的改善PLA的力学性能。
PLA, as a biodegradable material has received more and more attention, has been applied in the field of medical, packaging, and has good prospects. In this paper, it was focused on studying the thermal stability and extruding chain extension.
The change of molecular weight was studied with different water content, and melting temperatures. The results indicated that when PLA contained water, the averaged viscosity molecular weight decreased rapidly, the final balance of weight was related to moisture and melting temperature closely. The molecular weight of PLA which was drying completely decreased slowly. PLA with different moisture was dried to determine the appropriate drying temperature and drying time. The regulation of PLA degradation was estimated by TGA, and the effect factors of degradation were determined.
The extrusion was tested in the use of the material of vacuum dried PLA. The temperature of the extrusion and screw are the main factor for the PLA molecular weight. The result show that the decreasement of vacuum dried PLA is driven by the shear in the extruder and then the chemical degradation. The molecular weight distribution is narrowed when the situation of molecular weight decreasing is happening.
MDI, TGIC were used as chain extender, and chain extender were prepared with IPDI and small molecules which containing hydroxyl terminated. The molecular weight of PLA which changed with the addition of chain extender and compared with the changes of mechanical properties which joined flexible chains were studied. Averaged viscosity molecular weight increased and melting index lowed with the addition of chain extender increased. The polyether was good at improving mechanical properties of PLA compared with the polyester which contained the same chain length.
引文
[1]董炎明.高分子材料使用剖析技术[M].北京：中国石化出版社,1997
[2]李孝红,袁明龙,熊成东等.PLA及其共聚物的合成和在生物医学上的应用[J].高分子学报,1999,(3)：24-32
[3]阂思泽,吴魏.绿色化学与化工[M].北京：化学工业出版社,2000
[4]曾方,王文广,夏邦富.可生物降解高分子材料的研究进展及应用[J].塑料制造,2006,(8)：33-35
[5]瞿丽慢,肖沪卫.PLA领域国内外专利特点分析及我国对策[J].化学进展,2005,24(7)：818-819
[6]金关泰.高分子化学的理论和应用进展[M].北京：中国石化出版社,1995,1-128
[7]王方,汪朝阳,赵耀明.聚乙二醇改型PLA类材料的合成及应用[J].合成树脂及塑料,2003,20(6)：58
[8]李雪刚,张志艳等.PLA的合成及其应用[J].化工进展,2005,32(12)：1-5
[9]杨斌.绿色塑料PLA[M].北京：化学工业出版社,2007
[10]Kelly S. Anderson. Journal of Applied Polymer Science[J].2003.89(14):3757-3768
[11]Ke T, Sun X Z, et al. Thermodynamics of hydrogen bonding in polymer blends [J]. J Appl Polym Sci.2001,81:1203
[12]Martine 0, et al. Poly (lactic acid):plasticization and properties of biodegradable multiphase systems [J]. Polymer.2001,42:6209
[13]Sheth M, et al. Biodegradable polymer blends of poly (lactic acid) and poly (ethylene glycol) [J]. J Appl Polym Sci.1997,66:1495
[14]Nijenhuis A J, Colstee E, Grijpma D W, et al. High molecular weight poly (L-lactide) and poly (ethylene oxide) blends:thermal characterization and physical properties [J]. Polymer.1996,37(26):5849
[15]Coleman M M, et al. Thermodynamics of hydrogen bonding in polymer blends [J]. Macromolecules.1989,22:856
[16]Goh S H. Siow K S. Miscibility of poly(p-vinyl phenol) with polymethacrylates [J]. Polym Bull.1987,17:453
[17]Lianlai Zhang, S. H. Goh, S. Y. Lee et al. Miscibility and phase behavior of poly(D,L-lactide)/poly(p-vinylphenol) blends [J]. Journal of Applied Polymer Science.1998, 70(4):811-816
[18]Eguiburu J L. Blends of amorphous and crystalline polylactides with poly (methyl methacrylate) and poly (methyl acrylate) of miscibility study [J]. Polymer.1998,39:6891
[19]Zhang G B. Miscibility and phase structure of binary blends of polylactide and poly (methyl methacrylate) [J]. J Polym Sci, Part B:Polym Phys.2003,41:23
[20]Piorkowska. E, Galeski. A, Masirek. R. Polymer[J].2006.47(20):7178-7188
[21]Koyama N, Doi Y. Miscibility of binary blends of poly [(R)-3-hydroxybutyric acid] and poly[(S)-lactic acid] [J]. Polymer.1997,38(7):1589
[22]Ohkoshi I, et al. Miscibility and solid-state structures for blends of poly [(S)-lactide] with atactic poly [(R, S)-3-hydroxybutyrate] [J]. Polymer.2000,41:5985
[23]Zhang Jianfeng. Sun Xiuzhi. Biomacromolecules [J].2004.5(4):1446-1451
[24]Wang Ning. Yu Jiugao. Ma Xiaofei. Polymer International.2007.56(11):1440-1447
[25]Zhang Jianfeng. Sun Xiuzhi. Macromolecular Bioscience.2004.4(11):1053-1060
[26]Ke T, Sun X Z, et al. Effects of moisture content and heat treatment on the physical properties of starch and poly (lactic acid) blends [J]. J Appl Polym Sci.2001,81:3069
[27]Park J W. Miscibility and morphology in blends of poly (L-lactic acid) and poly (vinyl acetate-co-vinyl alcohol) [J]. Polymer.2003,44:4341
[28]Denise C, Li N. Maleation of polylactide (PLA) by reactive extrusion [J]. J Appl Polym Sci.1999,72(4):477
[29]Ke T, Sun X Z, etal. Processing and properties of extruded starch/polymer foams [J]. J Appl Polym Sci.2001,81:3639
[30]Ke T, Sun X Z, et al. Thermodynamics of hydrogen bonding in polymer blends [J]. J Appl Polym Sci.2001,81:1203
[31]谢吉星,杨荣杰.PLA在微型双螺杆中的挤出过程[J].高分子材料科学与工程2008,24(9)：116-119
[32]杨秀英,王晓波,李智华.挤出热历程对PLA流变性能和热性能影响[J].齐齐哈尔大学学报,2009,25(3)：1-4
[33]秦志忠,秦传香.PLA的热降解性能研究[J].合成纤维工业,2006,29(2)16-17
[34]钱刚,王海娟,周兴贵等.PLA热降解动力学[J].华东理工大学学报(自然科学版),2006,32(3)：249-253
[35]张普玉,彭李超,张予东.PLA/纳米SiO2共混物的热性能[J],高分子通报,2010,(2)：107-111
[36]张敏,崔春娜,黄继涛等.抑制PLA热老化的研究[J],塑料,2009,38(4)：85-87
[37]International Standard.Plastics-Small Enclosures for Conditioning and Testing Using Aqueous Solutions to Maintain Relative Humidity at Constant Value[S],ISO 483:1988
[38]付春华,李永刚,罗彦凤等.D,L-PLA热降解动力学研究[J]包装工程.2007,25(5)：7-9
[39]Babanalbandi A,Hill Djt,Hunter Ds,et al.Thermal Stability of Poly(lactic acid) before and after e-radiolysis[J] polymer International.1999,48:980-984
[40]谢吉星,杨荣杰.PLA在微型双螺杆中的挤出过程[J].高分子材料科学与工程,2008,24(9)：116-119
[41]郭文静,鲍甫成,王正.MAPP相容剂对WF/PLA复合材料性能的影响[J].塑料,2009,38(4)：7-9
[42]Tobias Villmow,Petra Potschke,Sven Pegel et al.Influence of twin-screw extrusion conditions on the dispersion of muti-walled carbon nanotubes in a poly(lactic acid) matrix.Plymer,2008,49:3500-3509
[43]Yaming Wang, Bernd Steinhoff, Christoph Brinkmann et al.In-line monitoring of the thermal degradation of poly(L-Lactic acid) during melt extrusion by UV-vis spectroscopy[J].Plymer,2008,49:1257-1265