星形聚乳酸

星形聚乳酸以其独特的结构与性能引起了人们的广泛兴趣,通常使用“先核后臂”法进行合成。本文根据不同类型的“核”进行分类,如小分子多羟基醇（天然糖醇）、无机（杂环）化合物的衍生物、金属有机化合物、多元酚的衍生物和星形高分子等,综述了星形聚乳酸近年来合成（尤其是丙交酯开环聚合法合成）、性能与应用等方面的研究进展,指出星形聚乳酸高分子量、低黏度、良好溶解性和热稳定性等优点有利于其在药物缓释等生物医用材料中的加工应用。     

羧甲基香菇多糖表面修饰的聚乳酸材料的表面性能研究

制备了香菇多糖羧甲基衍生物,再通过化学接枝方法利用共价键将羧甲基香菇多糖固定在氨基化聚乳酸基材表面,得到羧甲基香菇多糖化学接枝修饰的聚乳酸材料.此外,通过在氨基化聚乳酸基材表面进行羧甲基香菇多糖与壳聚糖的层层自组装,得到生物多糖层层自组装修饰的聚乳酸材料.采用扫描电子显微镜、水接触角测量仪、抗菌活性测试、溶血试验和血栓试验等方法对被修饰聚乳酸材料的表面性能和生物性能进行了分析和比较.结果表明采用2种表面修饰方法得到的羧甲基香菇多糖修饰的聚乳酸材料的亲水性、血液相容性以及对大肠杆菌抗菌活性得到改善.与化学接枝方法相比,经过羧甲基香菇多糖与壳聚糖层层自组装修饰的聚乳酸材料具有更好的亲水性、血液相容性和抗菌活性.     

聚乳酸接枝丙烯酰胺制备抗菌材料

采用自由基接枝聚合法,以过氧化苯甲酰为引发剂,制备聚乳酸接枝丙烯酰胺共聚物;对接枝共聚物进行氯化,制备表面含卤胺基团的抗菌聚乳酸高分子材料.考察了丙烯酰胺含量、引发剂浓度、聚合温度、聚合时间等对接枝率的影响.采用核磁共振氢谱、红外光谱等对接枝聚合物的分子结构进行了表征;利用溶液浇铸法,制备抗菌聚乳酸薄膜,并对薄膜的抗菌性能等进行了研究.结果表明:实验获得的卤胺接枝聚乳酸对大肠杆菌抗菌性能明显.     

聚乳酸链端烷基链长度对聚乳酸结晶性及水蒸气透过性的影响

分别以十二醇、十八醇、二十四醇和二十八醇为引发剂引发左旋丙交酯(L-LA)开环聚合,合成了链端键接不同长度烷基链的聚乳酸,利用红外吸收光谱(FTIR)、核磁共振氢谱(~1H-NMR)和凝胶渗透色谱(GPC)分析产物结构并计算产物的相对分子质量,通过示差扫描量热技术(DSC)对产物的结晶性能进行了分析,进一步通过薄膜水蒸气透过性实验分析了薄膜试样对水蒸气的透过性能.~1H-NMR和GPC分析结果表明,已将烷基链键接到聚乳酸链端,且固定L-LA与脂肪醇的摩尔比,不同脂肪醇引发合成的试样的相对分子质量基本一致,与理论值相差不大. DSC分析结果表明,在80℃时,聚乳酸的结晶速率随链端烷基链长度的增加而增加,链端为二十四烷基时,可促进聚乳酸在高温下成核,进而促进聚乳酸结晶.随相对分子质量增加,聚乳酸完全结晶时的结晶度略有降低.水蒸气透过性实验结果表明,非晶聚乳酸薄膜对水蒸气的透过能力强于结晶聚乳酸薄膜,聚乳酸的相对分子质量对薄膜的水气透过性影响不大,因此可通过调控聚乳酸的聚集态结构实现对水蒸气透过性的调节,进而将聚乳酸包装材料更好地应用于市场.     

基于聚乳酸的可降解形状记忆高分子的研究进展

综述了基于聚乳酸的可生物降解的形状记忆高分子材料的研究情况。首先介绍了形状记忆高分子材料的记忆效应、记忆机理,然后讨论了基于聚乳酸的三种类型的形状记忆高分子材料：单组份的聚乳酸类、聚乳酸共聚物类以及聚乳酸与无机物的复合材料,分别介绍了各种类型的形状记忆高分子材料的形状记忆性能和生物降解性能。最后,讨论了聚乳酸类记忆材料的应用情况,并对其研究前景和发展趋势进行了展望。     

多孔纳米羟基磷灰石-聚乳酸复合材料的

本文以TIPS法,在溶液中制备得到多孔纳米羟基磷灰石-聚乳酸复合材料,并对无机相与有机相之间的界面结合情况进行了研究,结果表明纳米羟基磷酸钙与聚乳酸基体之间结合良好。     

纤维/聚乳酸复合材料的研究进展

综述了天然纤维、合成纤维以及无机纤维增强聚乳酸(PLA)复合材料性能及研究进展,天然纤维包括麦秆纤维、菠萝叶纤维、竹纤维和蔗渣纤维等,合成纤维包括粘胶纤维、微纤化纤维素等,无机纤维中的玄武岩纤维和碳纤维,还比较了多种纤维增强PLA复合材料的力学性能。同时,对比了物理改性、化学改性以及增塑改性三种不同方法,对常用到的电晕处理、碱处理、偶联剂处理以及新型的等离子体处理、热蒸汽处理等对复合材料的影响作简要的阐述。最后,展望新型改性方法和生产技术的出现,以获得性能更优的绿色材料。     

聚乳酸在生物医药领域的改性研究进展

聚乳酸类材料是一种用途广泛的生物降解高分子材料,已经成为生物医用材料中最受重视的材料之一。但由于聚乳酸本身的缺陷,限制了其在生物医学工程中的应用。对聚乳酸的改性工作就一直备受关注。本文综述了近几年聚乳酸生物降解材料的物理改性和化学改性研究进展,经改性后聚乳酸的力学性能、降解性能、亲水性能和生物活性得到有效改善,从而更好地满足了生物医用需要。     

改性木纤维/聚乳酸复合材料的制备与性能研究

通过双螺杆挤出机共混制备了不同方法改性的木纤维/聚乳酸可生物降解复合材料,利用DSC、SEM、DMA、冲击和拉伸力学性能测试等手段,对比分析了木纤维的不同改性处理方式对复合材料热性能、界面形态和力学性能的影响.结果表明:复合材料的聚乳酸结晶动力学明显得到改善,木纤维促进了聚乳酸的异相成核过程.改性后的木纤维聚乳酸复合材料界面结合和力学性能均得到明显改善,以性能最优的硅烷偶联剂处理的木纤维和聚乳酸复合材料为例,其拉伸应力(62.1MPa)、杨氏模量(4525.0 MPa)和冲击强度(11.5k J/m~2)比纯聚乳酸分别提高2.9%,36.0%和14.0%.     

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     

Statistical and experimental investigation on low density microcellular foaming of PLA-TPU/cellulose nano-fiber bio-nanocomposites

This study dedicates to foaming of biocompatible blends of polylactic acid and thermoplastic polyurethane reinforced with bio-degradable cellulose nanofibers. This research primarily was associated with fabrication of PLA-TPU nanocomposites using a low weight fraction of cellulose nanofibers as a biodegradable reinforcement. Microstructural and mechanical properties of fabricated nanocomposites were examined and diffractometry was utilized to verify formation of percolated nanocomposites. Microcellular foaming was then performed with CO₂ as a blowing agent. Central composite design was applied in designing the experiments to evaluate the effects of main operating variables consisting of saturation pressure and time, heating time and foaming temperature. The results demonstrated that high saturation pressure and time promoted low cell diameters (below 5 μm) and high cell densities (above 10⁹ cell/cm³) due to the grown degree of crystallinity and higher PLA-TPU miscibility. Accordingly, adding TPU and CNF to the matrix create high crystalline foamed samples decorated with low bulk density.     

Poly(lactic acid)/coplasticized thermoplastic starch blend: Effect of plasticizer migration on rheological and mechanical properties

Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.     

Fire retardancy behavior of PLA based nanocomposites

To understand and improve the fire retardancy behavior of polylactic acid, we have incorporated two structurally different additives, sepiolite and organically modified montmorillonite. A novel approach (combination of electrospinning and extrusion/injection molding) is employed to address critical issues like char enhancement as well as the homogeneity/uniformity of the inorganic barrier during combustion of polymer nanocomposites. Fundamental knowledge is gained on the mechanisms of fire retardancy, particularly with samples of different thicknesses (thermally thin versus thermally intermediate/thick). Volumetric imaging of the residues provided a deeper understanding of the formation or the evolution of the inorganic barrier. Considerable insight on the dependency of biodegradation on the environment (primarily) and on the compromising effect of high aspect ratio nanoparticles is also obtained. This knowledge has a broader scientific impact and is critical to design the new generation of eco-benign flame retardant and biodegradable polymer nanocomposites.     

On the use of plant cellulose nanowhiskers to enhance the barrier properties of polylactic acid

Polylactic acid (PLA) nanocomposites were prepared using cellulose nanowhiskers (CNW) as a reinforcing element in order to asses the value of this filler to reduce the gas and vapour permeability of the biopolyester matrix. The nanocomposites were prepared by incorporating 1, 2, 3 and 5 wt% of the CNW into the PLA matrix by a chloroform solution casting method. The morphology, thermal and mechanical behaviour and permeability of the films were investigated. The CNW prepared by acid hydrolysis of highly purified alpha cellulose microfibers, resulted in nanofibers of 60–160 nm in length and of 10–20 nm in thickness. The results indicated that the nanofiller was well dispersed in the PLA matrix, did not impair the thermal stability of this but induced the formation of some crystallinity, most likely transcrystallinity. CNW prepared by freeze drying exhibited in the nanocomposites better morphology and properties than their solvent exchanged counterparts. Interestingly, the water permeability of nanocomposites of PLA decreased with the addition of CNW prepared by freeze drying by up to 82% and the oxygen permeability by up to 90%. Optimum barrier enhancement was found for composites containing loadings of CNW below 3 wt%. Typical modelling of barrier and mechanical properties failed to describe the behaviour of the composites and appropriate discussion regarding this aspect was also carried out. From the results, CNW exhibit novel significant potential in coatings, membranes and food agrobased packaging applications.     

生物可降解性聚羟基脂肪酸酯的化学合成研究进展

聚羟基脂肪酸酯是一种新型合成的脂肪族聚酯,同聚乳酸相似,具有优异的生物相容性能、生物可降解性和优良的力学机械性能,可作为生物医用材料和生物可降解包装材料,是最具前景的环境友好型聚合材料之一。目前合成聚乳酸和聚羟基脂肪酸酯的化学方法主要有开环聚合法、直接缩聚法以及自身酯交换聚合法,不过后者研究得较少。本文对这3种方法的研究进展进行了叙述,重点讨论了开环聚合法和直接缩聚法,尤其对开环聚合中的配位插入聚合的新进展进行了较详细的论述。     

Biodegradable polymer nanocomposites: An overview

Biodegradable polymer nanocomposites, due to their biodegradability and other improved properties possess tremendous scope in the industrial sector. This current article reviews the recent studies carried out over biodegradable polymer nanocomposites that includes preparation, characterization, properties, and applications of nanocomposites based on biodegradable polymers. An orderly introduction of nanocomposites prepared by using various biodegradable aliphatic polyesters and polymers obtained from biomass products has been brought about. A wide range of organic and inorganic nanoparticles was used as additives or fillers to prepare nanocomposites with improved desired properties. Considering vast research on layered silicates/polymer nanocomposites, a special emphasis has been summarized at the end of the review.     

Evaluation of commercially available polylactic acid (PLA) filaments for 3D printing applications

Journal of Thermal Analysis and Calorimetry - Polylactic acid (PLA) is a biodegradable and bioresorbable biopolymer that has successfully been applied in biomedical and related fields. It is in the...     

Biodegradation of Blown Films Based on Poly(lactic acid) under Natural Conditions

Summary: Commercially available polymer Bioflex® 219F, blend of polylactic acid and biodegradable co-polyester, was used for film preparation, performed on mono-extrusion blown moulding machine. Resulting thin film was investigated on biodegradability in composting conditions for 6 weeks. The influence of microbial attack on mechanical, physico-chemical properties, weight loss and surface morphology was tested weekly. The results obtained during 6 weeks of composting indicate relatively good accessibility to biological degradation. Moreover, the time course of studied properties was observed through the test period.     

Biodegradable poly(lactic acid)/chitosan-modified montmorillonite nanocomposites: Preparation and characterization

In this study, the biodegradable poly(lactic acid) (PLA)/montmorillonite (MMT) nanocomposites were successfully prepared by the solution mixing process of PLA polymer with organically-modified montmorillonite (m-MMT), which was first treated by n-hexadecyl trimethyl-ammonium bromide (CTAB) cations and then modified by biocompatible/biodegradable chitosan to improve the chemical similarity between the PLA and m-MMT. Both X-ray diffraction data and transmission electron microscopy images of PLA/m-MMT nanocomposites indicate that most of the swellable silicate layers were disorderedly intercalated into the PLA matrix. Mechanical properties and thermal stability of the PLA/m-MMT nanocomposites performed by dynamic mechanical analysis and thermogravimetric analysis have significant improvements in the storage modulus and 50% loss in temperature when compared to that of neat PLA matrix. The degradation rates of PLA/m-MMT nanocomposites are also discussed in this study.     

液相剪切原位剥离蒙脱土纳米片增强高阻氧聚乳酸

提出了液相剪切剥离蒙脱土(MMT)制备寡层纳米片(MNSs)并将其原位引入PLA基体的方法, 可经简单的刮刀涂覆法(Blade coating)制备MNSs质量分数为2%, 5%和10%的PLA基纳米复合薄膜. 该技术路线赋予了MNSs在PLA基体中充分剥离(片层间距可达3.11 nm)和良好取向排列以及较强的界面相互作用. 这些结构特征使得纳米复合薄膜的结晶度和力学性能得到大幅提升, 同时显著降低了氧气渗透系数. 本文不仅提出了可规模化原位剥离二维纳米片的有效方法, 更为制备高强高阻隔全降解复合材料及其结构-性能关系研究提供了思路.