溶剂诱导的聚乳酸/聚乳酸衍生物共结晶行为

通过溶液浇铸法制备不同组分的左旋聚乳酸(PLLA)和聚(L-2-羟基-3-甲基丁酸)(PL-2H3MB)共混物.运用差示扫描量热仪(DSC)、偏光显微镜(POM)、广角X射线衍射(WAXD)和热重分析仪(TGA)分析共混物的结晶、熔融行为和热稳定性.通过观察到DSC加热曲线中新的熔融峰判断PLLA和PL-2H3MB共晶...     

Biosourced Poly(lactic acid)/polyamide-11 Blends: Effect of an Elastomer on the Morphology and Mechanical Properties

Fully biobased polylactide (PLA)/polyamide-11 (PA11) blends were prepared by melt mixing with an elastomer intermediate phase to address the low elasticity and brittleness of PLA blends. The incorporation of a biobased elastomer made of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene oxide (PEO) copolymers was found to change the rigid interface between PLA and PA11 into a much more elastic/deformable one as well as promote interfacial compatibility. The interfacial tension of the polymer pairs and spreading coefficients revealed a high tendency of PEO to spread at the PLA/PA11 interface, resulting in a complete wetting regime (interfacial tension of 0.56 mN/m). A fully percolated rubbery phase (PEO) layer at the PLA/PA11 interface with enhanced interfacial interactions and PLA chain mobility contributed to a better distribution of the stress around the dispersed phase, leading to shear yielding of the matrix. The results also show that both the morphological modification and improved compatibility upon PEO addition (up to 20 wt %) contributed to the improved elongation at break (up to 104%) and impact strength (up to 292%) of the ternary PLA/PA11/PEO blends to obtain a super-tough multiphase system.     

聚乳酸/蒙脱土纳米复合材料的结构和热性能

聚乳酸/蒙脱土纳米复合材料的结构和热性能;聚乳酸;蒙脱土;纳米复合材料;插层     

The Influence of Peroxide on Bubble Stability and Rheological Properties of Biobased Poly(lactic acid)/Natural Rubber Blown Films

This study investigated the effects of natural rubber(NR)and an organic peroxide on the rheological properties,mechanical properties,morphology,and bubble stability during film blowing of poly(lactic acid)(PLA).The NR and peroxide contents were varied from 0 wt%to 25 wt%and 0 wt%to 0.5 wt%,respectively.The results confirmed that the presence of well-dispersed NR could significantly improve the toughness,elongation at break,and processability of PLA films,where the optimal amount of NR was 15 wt%.For the reactive blending with peroxide,a suitable peroxide content for good film toughness and clarity was 0.03 wt%,while the higher content of 0.1 wt%could provide slightly higher processability.These contents are considered much lower than that in the PLA system(without NR),which required up to 0.5 wt%peroxide.The rheological studies indicated that the melt strength,the storage modulus(G’)and complex viscosity(η*)at low frequency could be correlated with good film blowing processability of the PLA/NR films at low gel contents.These parameters failed to correlate in the films having high gel contents as the deformation rate experienced by each test was different leading to the different levels of response to the type and amount of gels.     

聚乳酸共混体系的研究进展

聚乳酸是人工合成的可生物降解的热塑性脂肪族聚酯 ,是一种环境友好的材料 ,逐渐成为人们研究的热点。本文根据聚乳酸共混体系中另一组分的生物降解性 ,将聚乳酸共混体系分为完全可生物降解共混体系和部分可生物降解共混体系两类。针对体系的相容性和结晶结构以及在提高PLA的性能和降低成本等方面 .综述了聚乳酸共混体系的最新研究进展 ,并对其发展动态进行了简要介绍     

Physical characterization of coupled poly(lactic acid)/starch/maleic anhydride blends plasticized by acetyl triethyl citrate

Acetyl triethyl citrate (ATC) was used as a plasticizer for poly(lactic acid) (PLA)/starch blends coupled with maleic anhydride and an initiator of 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (L101). Elongation of the blend at break was markedly increased when the ATC content was above the 8% loading level, which is referred to as the percolation threshold. The extended elongation was achieved at the expense of tensile strength and elastic modulus. Thermal transitions of the blend, including the glass transition temperature (T(g)), cold crystallization temperature (T(c)) and melting temperature (T(m)), decreased with ATC content. Thermally induced ATC migration affected the thermal behavior of the plasticized blends and reduced elongation and tensile strength, whereas the elasticity modulus increased. ATC migration increased with ambient temperature, which was controlled by the activation energy of the blend system. Leaching of ATC was slow at room temperature in distilled water, but significant in boiling water. Additionally, the leaching rate was also directly proportional to the ATC content of the blend. Glass transition temperatures of PLA/starch/MA/L101 blends with various acetryl triethyl citrate contents.     

High-Toughness Poly(lactic Acid)/Starch Blends Prepared through Reactive Blending Plasticization and Compatibilization

In this study, poly(lactic acid) (PLA)/starch blends were prepared through reactive melt blending by using PLA and starch as raw materials and vegetable oil polyols, polyethylene glycol (PEG), and citric acid (CA) as additives. The effects of CA and PEG on the toughness of PLA/starch blends were analyzed using a mechanical performance test, scanning electron microscope analysis, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray diffraction, rheological analysis, and hydrophilicity test. Results showed that the elongation at break and impact strength of the PLA/premixed starch (PSt)/PEG/CA blend were 140.51% and 3.56 kJ·m⁻², which were 13.4 and 1.8 times higher than those of pure PLA, respectively. The essence of the improvement in the toughness of the PLA/PSt/PEG/CA blend was the esterification reaction among CA, PEG, and starch. During the melt-blending process, the CA with abundant carboxyl groups reacted in the amorphous region of the starch. The shape and crystal form of the starch did not change, but the surface activity of the starch improved and consequently increased the adhesion between starch and PLA. As a plasticizer for PLA and starch, PEG effectively enhanced the mobility of the molecular chains. After PEG was dispersed, it participated in the esterification reaction of CA and starch at the interface and formed a branched/crosslinked copolymer that was embedded in the interface of PLA and starch. This copolymer further improved the compatibility of the PLA/starch blends. PEGs with small molecules and CA were used as compatibilizers to reduce the effect on PLA biodegradability. The esterification reaction on the starch surface improved the compatibilization and toughness of the PLA/starch blend materials and broadens their application prospects in the fields of medicine and high-fill packaging.     

开环聚合-固相缩聚法制备立体嵌段聚乳酸

首先,采用乳酸为引发剂,辛酸亚锡为催化剂,引发丙交酯开环聚合制得具有缩聚活性的L-聚乳酸和D-聚乳酸;然后,将两者熔融共混后进行固相缩聚,合成了一系列立体嵌段聚乳酸。采用核磁共振(NMR)、凝胶渗透色谱(GPC)及差示扫描量热仪(DSC)分析了产物的链结构、重均分子量、热性能,并探讨了均相晶体和立体复合晶体共存情况下的固相缩聚机理。结果表明,固相缩聚产物分子量增长的适宜反应条件为:反应时间30h,较低的催化剂含量,L-聚乳酸质量分数为80%。L-聚乳酸和D-聚乳酸共混物较低的初始立体复合晶体结晶度有利于后续固相缩聚过程中产物分子量的增长;固相缩聚不仅发生在异链之间,而且也发生在同链之间。     

Blends of Poly（lactic acid） with Thermoplastic Acetylated Starch

Blends of poly(lactic acid)(PLA) and thermoplastic acetylated starch(ATPS) were prepared by means of the melt mixing method. The results show that PLA and ATPS were partially miscible, which was confirmed with the measurement of Tg by dynamic mechanical analysis(DMA) and differrential scanning calorimetry(DSC). The mechanical and thermal properties of the blends were improved. With increasing the ATPS content, the elongation at break and impact strength were increased. The elongation at break increased from...     

聚乳酸荧光防伪纤维的制备及其性能

通过熔融纺丝法成功制备了聚乳酸荧光防伪纤维。分别采用DSC、XRD、纤维强度仪、荧光光谱仪、荧光显微镜等探讨了荧光粉含量对聚乳酸荧光防伪纤维的结晶结构、力学性能与荧光性能的影响,并利用激光共聚焦显微镜对防伪纤维进行了3D荧光分布模拟分析。研究结果表明:聚乳酸荧光防伪纤维在紫外光激发下,在530nm处出现最强发射峰,纤维呈黄绿色荧光;随着荧光粉含量的增加,纤维的荧光强度增加,但荧光粉在基体中的团聚现象逐渐加剧,纤维的断裂强度逐渐降低;激光共聚焦显微镜可较好地模拟荧光防伪纤维中荧光粉的分布情况。     

Hydrogen bonding assists stereocomplexation in poly(l‐lactic acid)/poly(d‐lactic acid) racemic blends

In this communication, we reported the sequence variation of stereocomplex crystals (SC) and homocrystals (HC) in poly(l ‐lactic acid)/poly(d ‐lactic acid) (PLLA/PDLA) racemic blends melts. It was evidenced that the emerging sequence of the SC and HC depends on the hydrogen bond formation in the melt, and the hydrogen bond is required for the stereocomplexation in PLLA/PDLA racemic blend. First, by combining a commercial fast‐scan chip‐calorimeter (Flash DSC 1) and micro‐FTIR, we found that hydrogen bonds were formed in the melt during cooling at 2.5 K/s, but not at 3000 K/s. Second, annealing the melt without hydrogen bonds at 100 °C led to HC emerging first, while annealing the melt with hydrogen bonds resulted in SC emerging at first. Third, the crystallization kinetics of the racemic blends after cooling to predefined T_c at 2.5 or 3000 K/s further verified that the hydrogen bonding can be inhibited effectively by cooling the racemic blends isotropic melt at fast enough rate. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 83–88     

静电纺丝法制备聚乳酸/纳米磷酸钙复合纳米纤维及其表征

首先合成了纳米磷酸钙(NCP),用扫描电镜(SEM)和X射线衍射(XRD)进行了表征.再利用静电纺丝法制备了PLA/NCP复合纳米纤维,对纤维进行了TEM,SEM,XRD以及单轴拉力测试的表征.TEM和XRD测试表明,NCP已成功掺杂到聚乳酸纤维中,获得的纤维为复合纤维.SEM测试表明,NCP在溶液中浓度较小时,复合纳米纤维的形貌变化不大;NCP浓度超过PLA质量的7%后,纤维表面出现粒状物;随着浓度继续增大,粒状物逐渐增多,最后很难成纤.拉伸实验结果表明,复合纤维拉伸强度先随着NCP浓度的增加而增大,但NCP浓度超过7%后拉伸强度随着浓度的增加反而减小.     

Tensile and Thermal Properties of Poly(lactic acid)/Eggshell Powder Composite Films

Biodegradable composite films of poly(lactic acid) (PLA)/eggshell powder (ESP) were prepared by the composite film casting method using chloroform as the solvent. ESP was loaded in PLA in 1 to 5 wt.%. The films were subjected to tensile, FT-IR spectral, thermogravimetric, X-ray, and microscopic analyses. The tensile strength and modulus of the composite films were found to be higher than those of PLA and increased with ESP content up to 4 wt.% and then decreased. A reverse trend was observed in the case of percentage elongation at break. The X-ray diffractograms of the composite films indicated an increase in crystallinity with ESP content. The optical micrographs indicated uniform distribution of ESP particles in the composite films. However, the fractographs indicated agglomeration of ESP particles at 5 wt.% loading. The FT-IR spectra revealed no specific interactions between PLA and ESP. The thermal stability of the composite films increased with ESP content.     

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。     

Phase Behaviour of Poly(styrene-co-methacrylic acid)/ Poly(styrene-co-N,N-dimethylacrylamide)/Poly(styrene-co-4-vinylpyridine) Ternary Blends by DSC and FTIR

Summary: we have investigated by DSC and FTIR the miscibility and phase behaviour of binary and ternary blends of different ratios of poly(styrene-co-methacrylic acid) containing 15 mol% of methacrylic acid (SMA15) with poly(styrene-co-N,N-dimethylacrylamide) containing 17 mol% of N,N,-dimethylacrylamide (SAD-17) and poly(styrene- co-4-vinylpyridine) containing 15 mol% of 4-vinylpyridine. SMA15 is miscible with both SAD17 and S4VP15 and interacts more strongly with S4VP15 than with SAD17 as evidenced by the positive deviations from linear average line observed with these blends and the appearance of new bands in the 1800–1550 cm⁻¹ region. This behaviour is known as ΔK effect. The FTIR study confirms that though the specific intermolecular interactions that occurred with each pair of the SMA15/S4VP15 and SMA15/SAD17 binary components are of different strength, they still exist in the ternary blend. Even though the three binary polymer pairs are individually miscible, the ternary system of SMA15/S4VP15/SAD17 exhibits only partial miscibility with small loop of immiscibility due to a significant ΔK effect. These results obtained by DSC and FTIR are in a fair agreement with theoretical prediction applying the Painter-Coleman association model.     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.