PAA对PLA流变性能和热性能的影响

通过熔融共混法制备了一系列的PLA/PAA共混物,考察了PLA/PAA共混体系的流变行为和热性能(结晶行为和热降解行为).FTIR测试结果证实PLA与PAA分子链之间形成了氢键网络.动态剪切流变测试和DSC测试均表明共混体系的流变行为和冷结晶行为会随着PAA含量的改变而改变,这可能是由于PLA与PAA的氢键作用受到PAA含量的影响.另外,DSC测试证实共混体系中的氢键网络还会受到试样热历史的影响.当PAA含量较低(低于5 wt%)时,PLA/PAA共混体系中PAA与PLA熔体两相的相分离不严重,使得PAA与PLA分子链能够较大限度地接触而形成较强的氢键作用,因而可以明显减缓增塑作用对黏度降低的影响.     

低含量聚乳酸对微孔发泡聚丁二酸丁二醇酯泡孔结构的改善

通过挤出制备了可生物降解聚丁二酸丁二醇酯(PBS)和3种聚乳酸(PLA)含量(7 wt%、15 wt%和20 wt%)的PBS/PLA共混物样品,采用超临界二氧化碳作为物理发泡剂对样品进行间歇发泡,研究发泡样品的泡孔结构,并分析其形成机理.在120oC发泡温度(Tf)下,借助PLA对PBS熔体黏弹性尤其是熔体强度的改善,获得了分布较均匀、形状较规则、直径较小(平均值约10μm)的微孔;共混物发泡样品的直径分布明显变窄,且符合高斯分布,这归因于细小的PLA相较均匀地分布于PBS基体中.进一步地,研究Tf对PBS和PLA含量为15 wt%的PBS/PLA共混物发泡样品泡孔结构的影响.结果表明,加入15 wt%的PLA使PBS的Tf下限从115oC降低至110oC,并显著改善了较高Tf(120和125oC)下制备的发泡样品内泡孔结构的均匀性.     

氯化镁/氯化1-丁基-3-甲基咪唑改性淀粉/聚丁二酸丁二醇酯共混材料的结构与性能

用氯化镁/氯化1-丁基-3-甲基咪唑([BMIM]Cl)复合增塑剂改性淀粉/聚丁二酸丁二醇酯(PBS)共混材料,采用红外光谱(FTIR)、扫描电子显微镜(SEM)、差示扫描量热分析(DSC)、X射线衍射分析(XRD)及力学性能测试等方法研究了氯化镁/[BMIM]Cl改性淀粉/PBS共混材料的结构和性能.结果表明,氯化镁能与淀粉及PBS形成较强的相互作用,从而破坏淀粉及PBS原有的氢键,导致淀粉/PBS共混体系结构和性能的改变.与[BMIM]Cl改性体系相比,氯化镁/[BMIM]Cl改性体系能进一步增强淀粉与PBS的界面结合力,提高共混体系的相容性;使淀粉/PBS的熔融焓、结晶度及结晶温度降低,冷结晶温度升高;提高共混体系的力学强度和断裂伸长率,抑制[BMIM]Cl因高效增塑产生的强度降低作用.采用氯化镁/[BMIM]Cl改性淀粉/PBS可制备出具有良好力学性能的淀粉/PBS共混材料.     

离子液体增塑改性玉米淀粉/聚丁二酸丁二醇酯共混材料的结构与性能

为考察离子液体对淀粉/聚丁二酸丁二醇酯(PBS)的作用效果,降低淀粉/PBS的脆性,以离子液体(1-丁基-3-甲基咪唑氯盐[BMIM]Cl)作为增塑改性剂通过熔融共混法制备了玉米淀粉/聚丁二酸丁二醇酯(PBS)共混材料,采用红外光谱(FTIR)、扫描电镜(SEM)、热重分析(TGA)、X射线衍射分析(XRD)及力学性能测试方法研究了[BMIM]Cl对淀粉/PBS共混材料结构和性能的影响.结果表明,[BMIM]Cl能与淀粉/PBS分子发生强相互作用,破坏淀粉/PBS共混物中原有的氢键与结晶结构,增强界面相互作用,改善相容性,进而改变淀粉/PBS共混材料的结构与性能;[BMIM]Cl的加入不影响淀粉/PBS的热稳定性,可使材料玻璃化转变温度(Tg)、结晶温度(Tc)、冷结晶温度(Tcc)及结晶度(Xc)降低.[BMIM]Cl具有显著降低淀粉/PBS脆性的作用,使其断裂伸长率大幅度增加,拉伸强度和弹性模量降低.     

聚丁二酸丁二醇酯与氯醚弹性体协同增韧改性聚乳酸多元共混体系

以来源于可再生资源聚丁二酸丁二醇酯(PBS)和氯醚橡胶(ECO)作为聚乳酸(PLA)的增韧改性剂,通过熔融共混的方法制备了PLA/PBS/ECO三元共混体系。动态力学分析和扫描电子显微镜结果表明,ECO促进了PBS和PLA之间的相容性。力学性能测试表明,ECO与PBS可实现对聚乳酸基体的协同增韧: PLA/PBS/ECO(70/20/10)显示出最优的拉伸性能,断裂伸长率高达270%;PLA/PBS/ECO(70/10/20)的冲击强度提高至23.7 kJ/m²,是纯聚乳酸的12倍。结合形态结构和冲击断面形貌分析表明ECO的存在可起到增容/增韧双重作用, 与柔性PBS产生良好的协同效应,有效改善聚乳酸材料的韧性。我们的研究表明,构造PLA-柔性生物聚酯和生物基弹性体多元共混体系是一种获得高性能生物基材料简单高效的手段。     

环氧呋喃树脂反应性增容改性聚乳酸/淀粉复合材料的研究

研究了环氧呋喃树脂反应增容改性聚乳酸/淀粉复合材料,对索氏提取法得到的淀粉进行1H-NMR、FTIR、XPS和静态接触角测试表征.结果表明在熔融共混过程中环氧呋喃树脂(FER)与淀粉及聚乳酸(PLA)发生化学反应,从而起到反应性增容的作用.另外,利用SEM、万能材料试验机和DSC分别对复合材料的界面相容性、机械性能以及热性能进行了表征,结果表明FER能够显著改善PLA和淀粉之间的界面相容性,在保持PLA高强度高模量的基础上,显著提高了PLA/starch复合材料的综合机械性能和结晶性能.     

聚乳酸/可分散性纳米二氧化硅复合材料等温结晶行为研究

采用超声辅助、熔融共混的方法,用可分散的纳米二氧化硅颗粒(DNS)对聚乳酸(PLA)进行改性处理,利用差示扫描量热法(DSC)、X射线粉末衍射分析(XRD)、FTIR等测试手段研究了DNS对PLA等温熔融结晶和等温冷结晶行为的影响,并且对测得数据用Avarmi方程进行处理,研究其等温结晶动力学.结果表明:DNS使PLA的等温熔融结晶和等温冷结晶的半结晶时间t_(1/2)减小、结晶速率提高,Avarmi指数n变化不大,说明DNS没有改变PLA结晶的成核机理.     

纤维素接枝共聚物对聚乳酸结晶性能和拉伸流变性能的影响

通过熔融缩聚法制备出含有聚乳酸支链的纤维素接枝共聚物(OLA-g-C),并采用溶液共混法制备一系列聚乳酸(PLA)/OLA-g-C共混物以及对比样聚乳酸/微晶纤维素(MCC)共混物.扫描电镜(SEM)结果表明聚乳酸支链的存在可以提高纤维素在PLA基体中的分散性,抑制团聚现象的出现.在非等温结晶过程中,OLA-g-C和MCC的加入都可以促进PLA的结晶,但是OLA-g-C的促进效果优于MCC,这与OLA-g-C在基体中的分散性良好有关.在等温结晶过程中OLA-g-C可以同时提高PLA的结晶度以及结晶速率,但对其成核机理和生长方式无明显影响.偏光显微镜(POM)观察的结果进一步证明OLA-g-C可以作为成核剂,有效地缩短基体的结晶时间,提高PLA的结晶能力.但是,OLA-g-C的加入却降低了体系的拉伸黏度,这与体系的缠结作用有关.     

流场中聚乳酸/聚碳酸酯共混体系的酯交换反应及其形态结构研究

选用钛酸四丁酯作为聚乳酸(PLA)/聚碳酸酯(PC)的酯交换反应催化剂,通过透射电子显微镜(TEM)和核磁共振氢谱(1H-NMR)研究了流场中不同组分比的PLA/PC共混体系酯交换反应机理及酯交换反应对不同组分比的共混体系相形态的影响.研究发现,无论在PLA/PC共混体系中是否含有催化剂,酯交换反应次数、参与酯交换反应的PC的含量、生成的共聚物中PC链段的含量及生成的共聚物的总质量和总摩尔数均随组分中PLA含量的增加而增加,催化剂的加入更拉大了这种差距.主要原因是与PC作为连续相相比,当PLA作为连续相时PLA链段沿界面的取向程度更高,从而导致进行多次酯交换反应的几率增加.添加催化剂后,影响酯交换反应的主导因素发生变化,从而导致PLA/PC 30/70体系界面反应的机理发生改变.钛酸四丁酯有效地促进了PLA/PC体系的酯交换反应,使分散相的尺寸都得到不同程度降低,尤其当PLA为连续相时催化产生的共聚物的总摩尔数更多,从而使PLA为连续相时的分散相粒径较PC为连续相时降低的更多.     

聚乳酸/矿物填料复合材料的示差扫描量热研究

通过熔融共混法制备了一系列聚乳酸(PLA)/矿物填料复合材料.采用示差扫描量热(DSC)研究了含有碳酸钙(CaCO3)、蒙脱土(MMT)和凹凸棒土(AT)的聚乳酸复合材料在不同热历程中的结晶和熔融行为.研究发现,MMT和AT对PLA的慢速降温结晶无明显影响,而碳酸钙在慢速降温过程中能够有效促进PLA结晶;在2.5 K/min的降温速率下,结晶热焓随碳酸钙含量增加而增加;填料种类和含量会对复合材料升温过程的冷结晶和熔融产生较大影响,低含量矿物填料主要对PLA的冷结晶起成核作用,其中MMT成核效果最好.较高含量下不同填料会对PLA晶体形态产生影响,从而得到多样的DSC曲线变化.     

Rheological and thermal behavior of PLA modified by chemical crosslinking in the presence of ethoxylated bisphenol A dimethacrylates

Crosslinking structures can be partly introduced into PLA by melt mixing in a twin screw extruder with dicumyl peroxide (DCP) and ethoxylated bisphenol A dimethacrylates (Bis‐EMAs) as a crosslinking coagent. The study of DCP and Bis‐EMA contents on the melt rheology, thermal properties, dynamic mechanical properties and morphology of the reactive extruded pellets is presented. The results show that PLA with a DCP content higher than 3 phr exhibits increases in both the melt modulus and complex viscosity as compared with PLA. The introduction of DCP into PLA improved the thermal stability of the PLA. PLAs with various Bis‐EMA contents showed the optimum storage modulus and complex viscosity to occur at 5 phr Bis‐EMAs. Moreover, the glass transition, cold crystallization and melting temperature of PLAs decreased with increasing Bis‐EMA content. The crystallinity of the partly crosslinked PLAs was lower than that of PLA. Similar to the rheological results, the thermo‐mechanical properties showed that the storage modulus and loss modulus of the partly crosslinked PLAs increased with increasing Bis‐EMA contents up to 5 phr. In addition, these partly crosslinked PLAs showed rough surface or sea island‐like structure. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of Carboxylic Acid Nucleating Agent on Crystallization and Mechanical Properties of PLA/PBS Blends

Poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) blends were prepared using a carboxylic acid salt as nucleating agent (NA). The effect of NA on the crystallization kinetics of PLA and PLA/PBS blend was investigated using a differential scanning calorimeter, a polarized optical microscope and a wideangle X-ray diffractometer. The crystallization rate of PLA component in PLA/PBS blends is increased effectively by NA through fast nucleation and growth rate of PLA α'-form crystal, which is confirmed by isothermal crystallization behavior of PLA/PBA/NA composites. The isothermal crystallization results also show that the incorporation of NA induces heterogeneous nucleation mechanism in PLA component. The increased number of crystal nuclei hinders the increase of average grain size of PLA component in composites but contributes to a higher crystallinity of both PLA and PBS components in PLA/PBS blends. Finally, the mechanical properties and dynamic mechanical properties of PLA/PBS/NA composites are improved because of the increased crystallinity, which are superior to that of PLA/PBS blend.     

Melt processing of maleic anhydride grafted poly(lactic acid) and its compatibilizing effect on poly(lactic acid)/poly(butylene adipate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) blend and their composite

Poly(lactic acid) (PLA)/poly(butylene adipate-co-terephthalate) (PBAT) blends were prepared using melt processing. The effects of maleic anhydride grafted PLA (PLA-g-MA) and calcium carbonate (CaCO₃) content on mechanical, thermal, and morphological properties of the blends were investigated. PLA-g-MA was synthesized by varying monomer and initiator contents using a reactive melt-grafting process. Tensile properties of PLA/PBAT blend were enhanced with adding 2 phr of PLA-g-MA. SEM micrographs exhibited the improvement of interfacial adhesion between PLA and PBAT in the compatibilized blend. Moreover, thermal stability of the blends improved with presence of PLA-g-MA. With increasing CaCO₃ content, Young’s modulus of the composites increased.     

Fully biodegradable blends of poly(butylene succinate) and poly(butylene carbonate): Miscibility, thermal properties, crystallization behavior and mechanical properties

Fully biodegradable poly(butylene succinate) (PBS) and poly(butylene carbonate) (PBC) blends were prepared by melt blending. Miscibility, thermal properties, crystallization behavior and mechanical properties of PBS/PBC blends were investigated by scanning electron microscopy (SEM), phase contrast optical microscopy (PCOM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and mechanical properties tests. The SEM and PCOM results indicated that PBS was immiscible with PBC. The WAXD results showed that the crystal structures of both PBS and PBC were not changed by blending and the two components crystallized separately in the blends. The isothermal crystallization data showed that the crystallization rate of PBS increased with the increase of PBC content in the blends. The impact strength of PBS was improved significantly by blending with PBC. When the PBC content was 40%, the impact strength of PBS was increased by nearly 9 times.     

生物基超韧聚乳酸复合材料的制备与性能

采用来源于可再生资源的聚醚酰胺弹性体（PEBA）增韧聚乳酸（PLA）制备超韧聚乳酸（PLA/PEBA-GMA）复合材料.为了提高PEBA与PLA之间的相容性,选择极性单体甲基丙烯酸缩水甘油酯（GMA）、共接枝单体乙烯基吡咯烷酮（NVP）及引发剂过氧化二异丙苯（DCP）对PEBA进行接枝改性制备PEBA-GMA.研究了接枝单体组分的用量（m/g）对PLA/PEBA-GMA复合材料性能的影响.研究发现,随着接枝单体组分用量的提高,复合材料的缺口冲击强度逐渐增大,当接枝单体组分GMA,NVP和DCP的用量分别为2.5,2.5和0.25 g时,复合材料的冲击强度高达88.6 kJ/m²,断裂伸长率为164.1%.研究表明,在熔融共混过程中,聚乳酸的端基（—OH和—COOH）与PEBA-GMA上环氧基团发生反应,有效改善两相间的界面相容性,随着接枝单体组分比例的提高,分散相PEBA-GMA的粒子尺寸逐渐减小且分布均匀.     

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on <Emphasis Type="Italic">in situ</Emphasis> Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC).By virtue of their similar chemical structures,in situ cross-linking reaction initiated by dicumyl peroxide (DCP) between PLA and PPC chains was realized in PLA/PPC blends.Therefore,the compatibility between PLA and PPC was increased,which obviously changed the phase structures and increased the elongation at break of the blends.The compatibilized blends had a recovery performance at 45 ℃.Combining the changes of phase structures,the mechanism of the shape memory was discussed.It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.     

MISCIBILITY, CRYSTALLIZATION AND MECHANICAL PROPERTIES OF PPC/PBS BLENDS

In this paper,melt blends of poly(propylene carbonate)(PPC)with poly(butylene succinate)(PBS)were characterized by dynamic mechanical analysis(DMA),differential scanning calorimetry(DSC),tensile testing,wide-angle X-ray diffraction(WAXD),polarized optical microscopy and thermogravimetric analysis(TGA).The results indicated that the glass transition temperature of PPC in the 90/10 PPC/PBS blend was decreased by about 11K comparing with that of pure PPC.The presence of 10% PBS was partially miscible with PPC.The 90/10 PPC/PBS blend had better impact ==========and tensile strength than those of the other PPC/PBS blends.The glass transition temperature of PPC in the 80/20,70/30,and 60/40 PPC/PBS blends was improved by about 4.9 K,4.2 K,and 13 K comparing with that of pure PPC,respectively;which indicated the immiscibility between PPC and PBS.The DSC results indicated that the crystallization of PBS became more difficult when the PPC content increased.The matrix of PPC hindered the crystallization process of PBS.While the content of PBS was above 20%,significant crystallization-induced phase separation was observed by polarized optical microscopy. It was found from the WAXD analysis that the crystal structure of PBS did not change,and the degree of crystallinity increased with increasing PBS content in the PPC/PBS blends.     

Structure and properties for biomass-based polyester blends of PLA and PBS

Structure and properties are studied for binary blends composed of poly(lactic acid) (PLA) and poly(butylene succinate) (PBS). The rheological measurements in the molten state reveal that the entanglement molecular weight of PLA is lower than that of PBS. Further, the interfacial tension of the immiscible blend system is evaluated employing a rheological emulsion model and found to be 3.5 [mN/m]. Moreover, thermal analysis directly detects that addition of PBS enhances the crystallization of PLA even though PBS is in a molten state. Further, the cold-crystallization for quenched blends occurs at lower temperature than that for a quenched PLA. This would be attributed to the nucleating ability of PBS, leading to generation of PLA crystallites during the quench operation.     

Significant enhancement of crystallization kinetics of polylactide in its immiscible blends through an interfacial effect from comb-like grafted side chains

A significant enhancement in isothermal crystallization kinetics of biodegradable polylactide (PLA) in its immiscible blends can be accomplished through blending it with a comb-like copolymer. PLA was blended with poly(ethylene glycol) methyl ether acrylate (PEGA) and poly[poly(ethylene glycol) methyl ether acrylate] (PPEGA, a comb-like copolymer), respectively. The results measured from phase contrast optical microscopy (PCOM) and differential scanning calorimetry (DSC) indicate that PLA and PEGA components are miscible, whereas PLA and PPEGA components are immiscible. The study of crystallization kinetics for PLA/PEGA and PLA/PPEGA blends by means of polarized optical microscopy (POM) and DSC indicates that both PEGA and PPEGA significantly increase the PLA spherulitic growth rates, G, although PLA/PPEGA blends are immiscible and the glass transition temperatures of PLA only have slight decreases. PPEGA component enhances nucleation for PLA crystallization as compared with PEGA component owing to the heterogeneous nucleation effect of PPEGA at the low composition of 20 wt%, while PLA crystallization-induced phase separation for PLA/PEGA blend might cause further nucleation at the high composition of 50 wt%. DSC measurement further demonstrates that isothermal crystallization kinetics can be relatively more enhanced for PLA/PPEGA blends than for PLA/PEGA blends. The “abnormal” enhancement in G for PLA in its immiscible blends can be explained by local interfacial interactions through the densely grafted PEGA side chains in the comb-like PPEGA, even though the whole blend system (PLA/PPEGA blends) represents an immiscible one.     

Poly(lactic acid)/poly(butylene succinate)/calcium sulfate whiskers biodegradable blends prepared by vane extruder: Analysis of mechanical properties,morphology, and crystallization behavior

Ternary blends of PLA/PBS/CSW with different weight fractions were prepared using a vane extruder. The mechanical properties, morphology, crystallization behavior and thermal stability of the blends were investigated. For the PLA/CSW blend, the tensile strength decreased, the flexural strength and modulus increased compared with pure PLA. For PBS, the addition of CSW had little influence on the mechanical properties. For the ternary blends PLA/PBS/CSW, the tensile strength, flexural strength and modulus decreased compared with pure PLA, while the elongation at break and the impact strength increased significantly. The brittle-ductile transition of the blends took place when the PBS weight fraction reaching 30 wt%. As a soft component in the blends, PBS was beneficial to improve the tensile ductility and the toughness of PLA. SEM measurements reveal that PLA/PBS/CSW blends were immiscible. When the weight fraction of PBS was 50 wt%, significant phase separation was observed, and CSW had preferential location in the PBS phase of the blend. DSC measurement and POM observation reveal that CSW had a heterogeneous nucleation effect on PLA and PBS matrix. The addition of PBS improved the crystallization of PLA and the thermal resistance of the PLA/PBS/CSW blends significantly.