超支化乙二胺三嗪聚合物对PPC/PBS共混体系的增强改性研究

以超支化乙二胺三嗪聚合物（HBETP）为改性剂，采用熔融共混法制备了聚碳酸亚丙酯（PPC）/聚丁二酸丁二醇酯（PBS）/HBETP共混物；利用动态热机械分析仪、热失重分析仪、电子万能试验机、旋转流变仪、扫描电子显微镜等，对其热性能、力学性能、流变性能、断面形貌等进行了表征。结果表明，当HBETP含量为0.5 %（质量分数，下同） 时，PPC/PBS/HBETP共混物在韧性基本保持不变的情况下，拉伸强度提高幅度最大，由7.56 MPa提高到11.22 MPa，增幅为49.6 %；HBETP的加入可以提高PPC/PBS的相容性，且适当的含量会使PPC/PBS的拉伸强度提升。     

聚碳酸亚丙酯与聚乳酸共混物性能及热分解动力学分析

采用溶液浇铸法制备了聚碳酸亚丙酯(PPC)/聚乳酸(PLA)共混物,通过力学性能测试、衰减全反射红外光谱分析、差示扫描量热分析和热失重分析研究了共混物的性能,并对共混物进行了热分解动力学研究。结果表明,随着PLA含量的增加,共混物的拉伸强度增大,断裂伸长率减小,PPC/PLA共混物的力学性能得到改善;随着PLA的含量从10%(质量分数,下同)增加到90%,共混物热失重10%所对应的温度(T-10%)从255℃逐渐增加到281℃,当PLA的含量分别为10%、50%和90%时,最大速率失重温度比纯PPC分别提高了3.45、15.51和41.58℃;采用Coats-Redfern法得出,PLA的加入能提高PPC的活化能,其中PLA含量为30%和50%时,共混物的活化能比纯PPC分别提高了12.72%和40.68%,说明PLA改善了PPC的热稳定性。     

端胺基型超支化聚合物对聚碳酸亚丙酯的改性研究

以乙二胺和三聚氯氰为原料,通过"一步法"合成了端胺基型超支化乙二胺三嗪聚合物(HBP);采用熔融共混法制备了HBP改性的聚碳酸亚丙酯(PPC)树脂,用差示扫描量热仪、热失重分析仪、微机控制电子万能试验机、组合式数显冲击试验机、旋转流变仪、扫描电子显微镜等对制备的PPC/HBP共混物进行了表征。结果表明,加入1.5%(质量分数,下同)的HBP,PPC/HBP共混物的拉伸强度和断裂伸长率分别提高了50.0%和55.4%;且HBP的加入使PPC的玻璃化转变温度(T_g)和热分解温度均有所提高;HBP是一种有效的PPC改性剂。     

MCC对PLA/PPC复合材料力学性能与热稳定性的影响

以微晶纤维素(MCC)作为改性剂,马来酸酐接枝聚乳酸(PLA g MAH)为界面相容剂,聚乳酸(PLA)、聚碳酸亚丙酯(PPC)为基体,通过熔融共混法制得PLA/PPC/MCC三元复合材料。采用控温拉伸、动态热分析、扫描电子显微镜以及热失重分析等方法研究了MCC对PLA/PPC的力学性能和热稳定性。结果表明,PLA/PPC/MCC三元复合材料的拉伸强度提高了12.7 %,玻璃化转变温度（Tg）提高了9.8 ℃;PLA g MAH的加入可以改善PLA/PPC/MCC三元复合材料的界面性质,从而提高力学性能和热稳定性;当PLA g MAH的添加量为5 %（质量分数,下同）时,三元复合材料在常温下的拉伸强度、弯曲强度和冲击强度分别提高了53.7 %、43.1 %和18.5 %;在60 ℃下三元复合材料的断裂强度提高了80 %;热降解温度以及最大失重温度与PLA/PPC相比分别提高了25.31 ℃和61.83 ℃。     

PLA/PPC/OMMT纳米复合材料的结构与性能研究

采用双螺杆挤出机制备了聚乳酸（PLA）/聚碳酸亚丙酯（PPC）共混物和PLA/PPC/有机改性蒙脱土（OMMT）纳米复合材料,采用偏光显微镜、差示扫描量热仪和力学性能试验机等对共混物和纳米复合材料的相态结构、熔融与结晶行为和力学性能等进行了研究。结果表明,在PPC含量低于30 %时,随着PPC含量的增加,PLA/PPC和PLA/PPC/OMMT体系中PLA的玻璃化转变温度（Tg）均降低,在PPC含量为50 %时出现了明显的相分离;随着PPC含量的增加,PLA/PPC的冲击强度增大;OMMT的含量小于1.5 %时,PLA/PPC/OMMT体系的结晶度、拉伸强度、断裂伸长率和冲击强度均随OMMT含量的增加而增大。     

制备方法对聚乳酸/聚丙撑碳酸酯性能的影响

通过熔融共混法和溶液浇注法制备了聚丙撑碳酸酯(PPC)与聚乳酸(PLA)的共混物。采用转矩流变仪、差示扫描量热仪、扫描电子显微镜、紫外可见近红外分光光度计等对共混物进行了表征,研究了共混方法对材料性能的影响。实验结果表明:PLA/PPC为部分相容性共混物,常温下放置体系会发生物理老化;PPC的加入使共混物的水蒸气阻隔性提高,随着温度的升高,共混物的水蒸气阻隔性明显降低,特别是PPC含量多的组分;PPC的加入还使共混物拉伸强度和杨氏模量降低,断裂伸长率提高。熔融共混会造成PPC和PLA的降解,降低体系黏度;相对于溶液浇注制备的共混物,其断裂伸长率较低,水蒸气阻隔性较好。     

长链型超支化聚合物对PLA/PPC共混体系的增容改性研究

将“一步法”合成的超支化聚酯进行接枝改性,得到末端带有大量脂肪酸长链的超支化聚合物（长链型超支化聚合物,LCHBP）,并采用红外光谱、核磁共振、羟值滴定等方法对其进行表征。以LCHBP为改性剂,对聚乳酸（PLA）/聚碳酸亚丙酯（PPC）进行不同程度的改性,制备了PLA/PPC/LCHBP熔融共混物,采用差示扫描量热仪、电子万能试验机、扫描电镜等,对其热性能、力学性能、断面形貌等进行表征。结果表明,加入不同含量的LCHBP后,共混体系的ΔTg出现不同程度降低,表明LCHBP的加入改善了PLA与PPC的相容性;与PLA/PPC体系相比,LCHBP的加入可使共混体系在保持拉伸强度基本不变的情况下,大幅提升断裂伸长率和冲击强度,其中当LCHBP的加入量为2.0 %时,冲击强度提高61 %,断裂伸长率提高367 %。     

PLA-g-GMA的制备及其对PLA/PPC共混体系性能的影响

采用双螺杆挤出机将甲基丙烯酸缩水甘油酯(GMA)接枝到聚乳酸(PLA)上,而后将接枝产物(PLA-g-GMA)与聚乳酸(PLA)、聚碳酸亚丙酯(PPC)反应性共混,考察了接枝物中GMA加入量变化对PLA/PPC/PLA-g-GMA共混体系的力学性能、热稳定性能的影响,并对共混体系的断裂机理进行了研究。结果表明,PLA-g-GMA的引入能够在一定程度上改善PLA与PPC的相容性。随着接枝物中GMA加入量的增加,共混物的冲击强度、断裂伸长率及拉伸强度均呈现出先升高后降低的趋势,并在接枝物中GMA加入量为3%时达到最大值。扫描电镜结果显示,PLA-g-GMA引入后共混物的韧性断裂特征越发显著,其冲击断裂方式由脆性断裂过渡为韧性断裂。热失重分析结果显示,加入PLA-g-GMA后共混物的起始分解温度和完全分解温度均有一定程度的提高。     

琥珀酸酐封端PPC对PLA共混体系性能的影响

采用琥珀酸酐封端的聚碳酸亚丙酯(SA-PPC)对聚乳酸(PLA)进行改性,在二月桂酸二丁基锡(DBTD)的催化作用下,通过熔融酯交换反应制备PLA/SA-PPC共混物,利用电子万能试验机、悬臂梁冲击试验机、差示扫描量热仪(DSC)和扫描电子显微镜(SEM)对其进行表征。分析了熔融反应机理及催化剂含量对共混物的力学性能、热性能及形貌的影响。结果表明,加入DBTD后,促进了PLA和SA-PPC间的酯交换反应,生成的共聚物和齐聚物分别具有增容作用及增塑作用。DSC和SEM结果表明,PLA与PPC的相容性显著提高。当DBTD含量为2份时,PLA/SA-PPC共混物的冲击强度和断裂伸长率分别由PLA的1.8 kJ/m²和8.7%提高至5.7 kJ/m²和318.6%,并且,拉伸强度下降不显著。     

可降解聚碳酸亚丙酯复合材料的性能

通过聚碳酸亚丙酯(PPC)与聚乳酸(PLA)的共混,提高PPC的热性能、力学性能、生物降解性。利用扫描电子显微镜(SEM)、多晶X衍射(XRD)、差示扫描量热(DSC)、热重分析(TG)、拉伸力学实验研究了复合材料的性能。实验结果表明,聚合物之间没有发生化学反应,共混物为部分相容的体系;复合材料的玻璃化转变温度最高比PPC提高30℃,分解温度Td5%最多比PPC提高42℃,Td50%最多比PPC提高67℃;PLA的加入使复合材料的降解性能优于PPC,40d降解后复合材料最大失重率为33.37%,是PPC的9倍;PPC-PLA复合材料有良好的成膜性,制备的薄膜透明均匀,复合薄膜材料拉伸强度为36～58MPa,杨氏模量最大为2943MPa。     

海水环境下聚碳酸亚丙酯/聚乳酸共混物的降解性能研究

研究了聚碳酸亚丙酯（PPC）/聚乳酸（PLA）共混物在海水环境下的降解性能,通过力学实验、扫描电子显微镜、衰减全反射红外光谱等分别研究了共混物的力学性能、表面微观形貌、化学结构等的变化规律。结果表明,随着降解时间的延长,10/90、30/70、50/50、70/30（质量比,下同）的PPC/PLA共混物的拉伸强度都不断增大,而断裂伸长率在30 d时急剧降低,此后几乎保持不变;海水作用下240 d后PPC和PLA表面都存在明显孔洞和缺陷,而50/50的PPC/PLA共混物表面没有明显的裂纹和孔洞;纯PPC和纯PLA的羟基指数、羰基指数以及乳酸指数都呈现不断增大的趋势,且在前30 d比较明显,而50/50的PPC/PLA共混物则几乎没有变化;共混物的质量损失主要体现在前30 d,且质量损失率几乎都小于10 %,降解程度较低;共混物失重5 %的热分解温度提高,而最大速率失重温度几乎没有变化。     

Thermal,mechanical, and morphological properties of polylactic acid toughened with an impact modifier

Polylactic acid (PLA) was melt‐blended with different amount (0 to 50 wt %) of a commercially available ethylene acrylate copolymer impact modifier. PLA/impact modifier blends were prepared via an internal mixer and compression molded into test specimens. The thermal, mechanical, and morphological properties of the blends were investigated. The addition of impact modifier decreased the ability of PLA to crystallize and/or recrystallize. The degree of crystallinity of PLA decreased while the cold crystallization temperature shifted to higher temperatures with increasing the impact modifier content. PLA/impact modifier blends were partially miscible. This was confirmed by the dynamic mechanical analysis (DMA) tests. With increasing the impact modifier content, the blends showed some improvement in the elongation at break and notched impact strength indicating the toughening effects of the impact modifier. In contrast, the yield stress and tensile modulus decreased with the increase in the impact modifier content. Scanning electron microscopy (SEM) micrographs revealed that the toughening mechanisms among others involved shear yielding or plastic deformation of the PLA matrix induced by interfacial debonding between the PLA and the impact modifier domains. PLA with 30 wt % impact modifier showed comparable yield stress and tensile modulus and better elongation at break and impact strength (+90%) than those of polypropylene (PP). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123:2715–2725, 2012     

Mechanical,morphological, thermal properties and hydrolytic degradation behavior of polylactic acid/polypropylene carbonate blends prepared by solvent casting

The preparation of polylactic acid (PLA) and polypropylene carbonate (PPC) blend films by using the solvent casting method is to improve the properties of pure PLA. The blends' mechanical and thermal properties, morphological as well as hydrolytic degradation behavior are evaluated. The tensile test proved that the increase of PPC from 0 wt% to 75 wt% could improve the elongation of pure PLA when the graph showed a significant increase of the elongation from 10% to 1000%. Scanning Electron Microscopy (SEM) supported the significant increase in elongation of the blends when it shows a definite phase separation in 75/25 PLA/PPC, where 25% of PPC has formed islands in the PLA matrix. Differential scanning calorimetry indicates the partial miscibility of the blends where two peaks of the glass transition temperature moved towards each other when the amount of PPC increases. Fourier transform infrared (FTIR) spectroscopy revealed a possible intermolecular interaction between two polymers, which affects the miscibility of the blends. Finally, the hydrolytic degradation test indicates that the degradation started from the PLA phase and the blends' degradation rate decrease as wt% of PPC increase.     

Preparation and characterization of poly(lactic acid)/recycled polypropylene blends with and without the coupling agent,n-(6-aminohexyl)aminomethyltriethoxysilane

Blends of polylactide (PLA) and recycled polypropylene (rPP) were prepared by melt-processing using a corotating twin-screw extruder and subsequent pelletizing of the extrudates for injection molding. The PLA/rPP blends were characterized by Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), rheometer (MCR-102), scanning electron microscopy(SEM), tensile tests, and impact measurements. The results indicate that the PLA/rPP blend is immiscible and has a two-phase structure. TGA revealed enhancement of the thermal stability of the blends upon addition of rPP. The storage modulus, loss modulus, and complex viscosity of the blends increased with rPP concentration. Mechanical studies showed that introduction of rPP results in a decrease in tensile strength and modulus and enhancement of the impact strength of PLA in the blends. The effects of a silane coupling agent on the morphology and on the tensile and impact properties of the rPP blends of silane-modified PLA were also examined. SEM studies suggest that silane is an effective interfacial modifier. Thus, better interfacial adhesion was observed with silane-modified blends as compared with unmodified blends. Silane also improved the mechanical properties of the modified blends. The blends reached maximum tensile strength at 1.5 wt.% silane (relative to modified PLA content), and impact strength increased with increasing silane concentration. These results confirm the enhancing effect of silane on modified PLA/rPP blends.     

Effect of organoclay on non-linear rheological properties of poly(lactic acid)/poly(caprolactone) blends

The nonlinear viscoelastic properties of PLA/PCL blends with and without clay (montmorillonite, MMT) under large amplitude oscillatory shear (LAOS) flow were investigated. The G′ and G″ as a function of strain amplitude, Lissajous plots and FT-rheology methods were used to interpret nonlinear behavior of PLA/PCL blends with and without MMT. Additionally, scanning electron microscopy (SEM) images of PLA/PCL with MMT blends were taken to investigate the effects of clay on the internal structure of the PLA/PCL blends. A relationship between morphological changes and linear and nonlinear rheological properties was observed. SEM image analysis revealed that clay acted as a compatibilizer and then reduced the size of droplets in the PCL domain of the PLA matrix. As a result, nonlinear properties sensitively reflect morphological changes with increasing MMT amount. The nonlinear rheological properties of PLA/PCL/MMT/metallocene-LLDPE (mLLDPE) were also investigated when mLLDPE was used as an impact modifier to improve mechanical properties, and the nonlinear rheological properties of PLA/PCL/MMT and PLA/PCL/MMT/mLLDPE were also compared.