【作者】 王宁；

【导师】 于九皋；

【作者基本信息】 天津大学 ， 高分子化学与物理， 2007， 博士

【摘要】 本文采用熔体共混与复合技术,将PLA分别与热塑性淀粉(TPS)、乙酰柠檬酸三丁酯(ATBC)、聚己二酸-1, 3-丁二醇酯(PBA)和纳米炭黑(CB)进行共混、增塑和无机纳米填料复合等改性以提高PLA的性能和实用性。PLA与热塑性淀粉(TPS)进行共混,不仅降低PLA材料的成本,还提高其应用性能。实验证明,水含量对淀粉的塑化至关重要,干燥的淀粉很难塑化完全;同时也发现,水的存在使PLA在熔融加工过程中会发生水解,导致PLA分子量降低,性能恶化。为了提高无水淀粉的塑化效果,改善无水热塑性淀粉(DTPS)与PLA共混体系的分散性,首先采用柠檬酸(CA)为无水淀粉的促塑化剂和PLA/DTPS共混体系的相分散剂。研究发现基于干燥淀粉质量2%的CA就能够显著提高其塑化效果和熔体流动性,从而有效改善PLA/DTPS共混体系的分散性。采用过氧化二异丙苯(DCP)引发马来酸酐(MAH)接枝PLA为反应型增容剂,使用“两步法”挤出工艺对PLA/DTPS共混体系进行增容改性。实验证明, PLA/DTPS共混体系在MAH和CA共同作用下,两相之间的分散性和相容性显著提高,PLA/DTPS共混体系的性能得到明显改善,体系的拉伸强度可达40MPa,优于PLA自身强度。根据实验结果,总结出CA和MAH对PLA/DTPS共混体系有分散–接枝协同增容作用。柠檬酸酯类增塑剂虽然能够有效增塑PLA,但由于析出严重而影响柠檬酸酯的应用。本文首次采用PBA作为PLA增塑剂,对比研究发现当增塑质量大于20wt%时,PBA较ATBC具有更高的增塑效率。PBA增塑的PLA体系的断裂伸长率可达到600%以上,并且能够保持23.7MPa的拉伸强度。PBA的加入能够有效降低增塑PLA膜的水蒸气透过率,改善PLA熔体流动性和加工性能。CB不仅能够提高PLA材料的拉伸强度,还可以获得可生物降解导电聚合物,并且通过控制复合体系中增塑剂与CB的浓度使材料的电导率可控。将CB经ATBC或PBA浸润处理后,可以显著提高CB与PLA基体之间的相容性,从而获得高分散PLA/CB复合体系。加入增塑剂后,PLA/CB复合体系的电导率提高了1个数量级,体系的拉伸强度和断裂伸长率可以分别保持在45MPa和100%以上,具有良好的应用前景。此外,CB的加入还有效抑制了共混体系中增塑剂的迁移和水蒸气透过率。更多还原

【Abstract】 In this paper Poly (lactic acid) (PLA) is blending, plasticizing, compositing modified with thermoplastic starch (TPS), acetyl tributyl citrate (ATBC), Poly(1,3-butylene adip ate) (PBA) and carbon black (CB) to improve the properties of PLA through melting blending technique respectively.After blending PLA with TPS, not only can decrease the cost of PLA, but also increase the application. Water is realized as an important plasticizer for the plasticization of TPS during research. It is impossible to achieve high plasticized dry starch in the present of glycerol. At the same, PLA can be depolymerized in the presence of water at elevated temperatures, which decreases the molecular of PLA and results in poor mechanical properties. In order to increase the plasticization of dry starch and the dispersion in immiscible PLA/thermoplastic dry starch (DTPS) blend, citric acid (CA) is used as plasticization accelerant and dispersant for DTPS and PLA/DTPS blend respectively. 2wt% CA can dramatically increase the plasticization and the fluidity of DTPS. So the dispersion between PLA and DTPS can be increased in our research.Maleic anhydride (MAH) with initiator Dicumyl peroxide (DCP) is used as reactive compatibilizer to increase the compatibility in PLA/DTPS blend through two step extrusion processing. In the present of MAH and CA, the dispersion and compatibility in PLA/DTPS blend dramatically increased in our research. So a high performance PLA/DTPS blend can be achieved. The tensile strength of PLA/DTPS blend can reach to 40MPa, which is higher than pure PLA. Moreover the compabilizing mechanism of phase dispersion-grafting synergism in PLA/DTPS blends is advanced.ATBC is a kind of environment friendly plasticizer which can plasticize PLA effectively. But the plasticization and application of PLA is dramatically influenced by the migration of ATBC. So in this paper PBA as a novel plasticizer is used to plasticize PLA. Compared with ATBC, PBA is more effective to plasticize PLA when the plasticizer content is higher than 20wt%. The elongation at break of PBA plasticized PLA can excess 600%, and the tensile strength keep 23.7MPa. So PBA has stronger practicability. Moreover hydrophobic plasticizers can also increase melting processing and water vapor permeability properties.CB not only can increase the tensile strength of PLA, but also conductive polymer composites came from renewable source can be achieved. And the electrical conductivity can be controlled by the content of CB and plasticizer. The compatibility between PLA and CB dramatically increases after CB is dipped by ATBC or PBA. So a high dispersion PLA/CB composite can be achieved. In the present of plasticizer the electrical conductivity of PLA/CB composite increase 1 quantity class. Moreover the tensile stress and elongation at break keep at 45MPa and 100% respectively. Finally the migration of plasticizer and water vapor permeability are restrained in the present of CB.更多还原