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利用双螺杆挤出机将低分子量的乳酸预聚物在挤出机上进一步缩聚,制备出较高分子量的聚乳酸.研究了反应挤出温度、催化剂用量及螺杆转速等因素对该缩聚反应的影响.结果表明,当反应温度为160℃,催化剂用量为0.5%,螺杆转速为30 r/min时,聚乳酸的分子量能得到最大程度的提高. 相似文献
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采用熔融缩聚法制备聚L-乳酸(PLLA)和聚D-乳酸(PDLA)预聚物;将相对分子质量相近的PLLA和PDLA预聚物分别溶于二氯甲烷中,进行溶液共混,制备部分或全部立构复合聚乳酸(sc-PLA);采用固相聚合的方法提高sc-PLA的相对分子质量,并对sc-PLA的结构和性能进行了表征。结果表明:sc-PLA的熔点比聚乳酸约高55℃,且与立构复合晶体结构有关;随着共混物中PLLA含量的增加,固相聚合后,scPLA的相对分子质量增加;立构复合结构的形成并不能提高sc-PLA的热降解温度,提高相对分子质量能明显提高sc-PLA的热稳定性,且相对分子质量越大,sc-PLA初始热降解温度越高,最高可达270℃。 相似文献
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以端羟基聚乳酸(PLA)、聚己二酸-丁二醇-尿素(PBAu)为预聚物,六亚甲基二异氰酸酯(HDI)为扩链剂,制备出一种新型PLA/PBAu嵌段共聚物。研究了扩链剂用量、扩链温度以及催化剂用量对PLA/PBAu嵌段共聚物分子量的影响,确定了合成PLA/PBAu嵌段共聚物的最佳工艺条件。采用核磁共振、凝胶渗透色谱、差示扫描量热仪、扫描电镜等对共聚物薄膜结构及性能进行表征。结果表明:成功合成了PLA/PBAu嵌段共聚物,分子量可达10×104,玻璃化转变温度约为41℃;并且随着PBAu含量的增加,共聚物的结晶度逐渐增加。以NaOH溶液为模拟液进行加速降解实验发现,当PBAu含量为30%时,可以显著提高嵌段共聚物的降解速率,并且通过调节PLA、PBAu预聚物的含量,可以控制嵌段共聚物的降解速率。 相似文献
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以端羟基聚乳酸(PLA)、聚己二酸-丁二醇-尿素(PBAu)为预聚物,六亚甲基二异氰酸酯(HDI)为扩链剂,制备出一种新型PLA/PBAu嵌段共聚物。研究了扩链剂用量、扩链温度以及催化剂用量对PLA/PBAu嵌段共聚物分子量的影响,确定了合成PLA/PBAu嵌段共聚物的最佳工艺条件。采用核磁共振、凝胶渗透色谱、差示扫描量热仪、扫描电镜等对共聚物薄膜结构及性能进行表征。结果表明:成功合成了PLA/PBAu嵌段共聚物,分子量可达10×10~4,玻璃化转变温度约为41℃;并且随着PBAu含量的增加,共聚物的结晶度逐渐增加。以NaOH溶液为模拟液进行加速降解实验发现,当PBAu含量为30%时,可以显著提高嵌段共聚物的降解速率,并且通过调节PLA、PBAu预聚物的含量,可以控制嵌段共聚物的降解速率。 相似文献
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MAPP相容剂对WF/PLA复合材料性能的影响 总被引:2,自引:2,他引:0
研究了不同MAPP相容剂对木纤维/聚乳酸(WF/PLA)复合材料物理力学性能、熟性能及PLA分子量的影响.结果表明:低分子量的MAPP(CA60)相容剂使复合材料制备过程中PLA降解更严重,复合材料耐水性降低;纯MAPP(H1100P)相容剂,可明显提高复合材料耐水性,但不能改善其弯曲强度;由MAPP与PP共混的M300相容剂可抑制复合材料制备过程中PLA的降解,也能提高复合材料的弯曲强度和耐水性,是较好的WF/PLA复合材料相容剂.MAPP相容剂的作用与相容剂在复合材料制备过程中对PLA分子降解的抑制作用有关. 相似文献
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以聚乳酸(PLA)、聚乙二醇(PEG)为原料,采用溶液共混法制备出不同分子量的PEG与PLA的复合材料,并通过偏光显微镜(PLM)、差示扫描量热仪(DSC)、X射线衍射仪(XRD)对PLA/PEG复合材料的结晶行为进行了研究。结果表明:纯PLA在实验条件下不能结晶,而PEG的加入促进了PLA结晶;PLA的结晶温度和结晶度随PEG分子量的增大而降低,熔点随PEG分子量的增大而提高;PEG的加入促使实验条件下不能结晶的PLA生成α型晶体,但PEG分子量的变化对PLA的晶型基本没有影响。 相似文献
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聚乳酸立构复合物的研究现状与进展 总被引:1,自引:1,他引:0
聚乳酸作为生物可降解材料的一种,对环境友好、无毒害,可应用于组织工程、药物缓释等生物医用材料,以及石油基塑料的替代材料.聚乳酸立构复合结构(PLA Stereocomplex,SC),由于特有的晶体结构可以明显提高PLA的耐热性等,从而进一步扩大了PLA的应用范围.综述了聚乳酸立构复合结构的制备方法、性能及表征,以及近年来的研究现状与发展趋势. 相似文献
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A long‐alkane‐segment semicrystalline polyamide based on 1,12‐diaminododecane and 1,12‐dodecanedicarboxylic acid was synthesized and characterized. The polymer was prepared by melt polycondensation. The molecular weight of the material ranged from 20,000 to 40,000 g/mol, depending on the polymerization conditions. The resulting product was characterized by means of elemental analysis, infrared spectrometry, 1H‐ and 13C‐NMR, intrinsic viscosity, differential scanning calorimetry (DSC), thermogravimetric analysis, dynamic mechanical analysis, and wide‐angle X‐ray diffraction (WAXD). Some mechanical properties were measured. In addition, the thermal behavior of nylon 12,14 was systematically investigated with DSC and variable‐temperature WAXD. Double endotherms were observed during the melting of the polymer, which might have originated from the melt and recrystallization processes of nylon 12,14 on heating. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1581–1589, 2003 相似文献
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提出了用同相缩聚法生产聚酯中黏切片的新工艺。与熔融缩聚工艺流程相比,用新工艺生产的产品颗粒小,可提高固相反应速率;结晶度高(50%~55%),可省略使用过程中的结晶工序;乙醛含量低,约为熔融缩聚法的1/3.可提高最终产品的热稳定性。由于新工艺流程未使用有动力设备的最终缩聚釜,运行费用可减少20%,并减少了维修费用。 相似文献
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乳酸直接缩合法合成聚乳酸类生物降解材料 总被引:15,自引:0,他引:15
与传统的采用丙交酯单体开环聚合法相比 ,直接缩合法使合成流程缩短 ,工艺简化 ,有利于聚乳酸及其衍生物产品的开发和应用。其中 ,溶液聚合可以比熔融聚合获得相对较高的相对分子质量 ,但熔融聚合法较溶液聚合法的工艺更简单 ,适宜于制备扩链反应的预聚体。无催化剂的熔融聚合法还可以直接合成药物缓释材料 相似文献
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Taking advantage of a melt polycondensation process, a series of copolyesters composed of pure terephthalate acid (PTA), ethylene glycol (EG), and 1,3‐propanediol (1,3‐PDO) were synthesized. The component, molecular weight, molecular weight distribution, and thermal properties of the copolymers were characterized. The results show that the contents of trimethylene terephthalate (TT) units in the resulting copolyesters are higher than PDO compositions in original diol. Oligomer content in the copolyesters varies with the compositions and attains a minimum value when the TT ingredient is 49.52 mol %. The glass transition temperature (Tg) of the copolyesters varies from 78.5°C for PET (polyethylene terephthalate) to 43.5°C for PTT (polytrimethylene terephthalate) and decreases monotonically with the components. The copolyesters are amorphous copolymers when TT content is in the range of 32.4–40.8 mol %, as calculated from the melting enthalpy (ΔHm) measured via differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1511–1521 2006 相似文献
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通过对聚酯装置增容和后接直纺长丝前后熔体齿轮泵工况变化的统计分析,研究其运行不稳定的原因,提出改造措施,包括滑动轴承润滑油槽,齿轮泵的机械密封,降低齿轮泵出口压力,改自动提速为手动提速等等。 相似文献
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This article describes a new, nonphosgene method for the synthesis of poly(bisphenol A carbonate) (PC). The method involves three steps: the reaction of an aliphatic diol with phenyl chloroformate to form an alkylene diphenyl dicarbonate, the reaction of the alkylene diphenyl dicarbonate with bisphenol A to produce an aromatic–aliphatic polycarbonate, and the thermal treatment of the polycarbonate at 180–210°C under a stream of nitrogen with Ti(OBu)4 to give PC and a cyclic alkylene carbonate. The method furnished low to moderate molecular masses of PC upon the complete elimination of the aliphatic moieties. The approach may be considered a new method, based on polycarbonate thermochemical degradation, for the synthesis of cyclic aliphatic carbonates. The obtained polymers were characterized by intrinsic viscosity and IR, 1H‐NMR, and 13C‐NMR spectroscopy. The thermal treatment step was conducted in a glass reaction tube at 180–210°C under a stream of nitrogen, and the reaction was completed by heating to 250°C. In the thermal treatment step, semisolid effluents composed of cyclic alkylene carbonates were formed and subsequently eliminated from the reaction mixture. Heating to 250°C under nitrogen or under a dynamic vacuum furnished the pure aromatic PC residue. This intrachange reaction provides a flexible method for the synthesis of polycarbonates with alkylene diols containing two or three methylene groups, from which the pure PC homopolymer can be prepared. The potential of this approach was demonstrated by the successful synthesis of PC homopolymer from five different polycarbonates with a bisphenol A unit linked to 1,2‐propylene, 1,3‐propylene, 2‐methyl‐1,3‐propylene, 2,2‐dimethyl‐1,3‐propylene, and 1,3‐butylene as the alkane chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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