完全降解聚乳酸共混复合材料的研究进展

聚乳酸(PLA)是可完全生物降解的材料,广泛应用于包装、纺织、生物医用等领域。但其具有性脆,价格较高,疏水性大等缺点,限制了应用发展。近年来对聚乳酸共混改性已成为研究热点。根据共混组分的生物降解性,聚乳酸共混体系分为完全生物降解体系和部分生物降解体系。文中综述了近年来完全生物降解聚乳酸共混体系的研究,主要阐述了PLA/淀粉、PLA/天然纤维复合材料,并简要介绍了PLA/甲壳素、PLA/蛋白等PLA/天然高分子复合材料,以及PLA/PCL、PLA/PPC、PLA/PEO等PLA/合成高分子复合材料。     

聚乳酸基生物可降解材料的相容性

随着能源危机和环境污染的日益严重,生物可降解塑料逐渐成为研究的趋势和热点。聚乳酸(PLA)具有良好的生物降解性、生物相容性、可再生性、高强度、易加工等优点,被认为是最有前途的生物降解聚合物之一。聚乳酸的延展性和冲击性能较差严重制约了PLA的应用,共混改性是一种经济有效的方法,从而解决其韧性不足的缺点。然而,PLA在热力学上与大多数聚合物不相容,为了获得性能优良的PLA共混材料,聚合物共混过程中需要加入一种有效的相容剂进行增容。近年来,PLA与不同聚合物共混时的相容性研究已取得一定进展,本文就其进展进行全面综述。     

含功能化咪唑鎓离聚物增韧改性聚乳酸的研究

以生物质来源的氯醚弹性体和羟乙基咪唑、PEG端咪唑单体为原料,通过简单的季胺化和离子交换反应,成功制备了2种新型功能化的生物基离聚物(ECO-OH-PF_6,ECO-EG-PF_6),并将其应用于聚乳酸的共混增韧改性.离聚物ECO-EG-PF_6呈现典型的弹性体特征,而ECO-OH-PF_6表现为塑料性能.在聚乳酸(PLA)与离聚物共混体系中,ECO-OH-PF_6表现出对PLA更优的增韧效果. PLA/ECO-OH-PF_6(80/20)共混物断裂伸长率可提高至241%,而拉伸强度可保持在47.8 MPa.动态机械分析和扫描电子显微镜的结果表明离子-偶极相互作用和氢键相互作用使得ECO-OH-PF_6与PLA组分之间具有良好的相容性,形成了较强的界面粘附.而且由于折光指数相匹配,PLA/ECO-OH-PF_6共混物表现出良好的透明性,可见光范围内的透过率可达77%～87%.因而ECO-OH-PF_6可成为PLA良好的增韧改性剂,促进PLA基材料在透明包装等领域获得广阔的应用.     

高熔体强度聚乳酸的研究进展

聚乳酸(PLA)具有完全可再生、完全可降解、生物相容等优异的综合性能,在一次性餐具、日用品、包装材料、纺丝和3D打印等领域具有广阔应用前景。但是,由于PLA是直链脂肪族聚酯,其熔体强度低,导致PLA在使用发泡、熔融纺丝、吹膜、热成型等基于拉伸流动场的加工成型方法时工艺性能较差。因此,提高PLA的熔体强度对于改善其加工性能和促进其产业化推广具有重要的意义。本文综述了改善PLA熔体强度的技术研究进展,主要包括共聚技术、扩链改性技术、自由基反应技术和纳米技术等。     

聚(3-羟基丁酸酯-co-3-羟基戊酸酯)改性及纤维成形北大核心CSCD

聚(3-羟基丁酸酯-co-3-羟基戊酸酯)(PHBV)是一种微生物发酵生产的热塑性聚合物。从物理、化学改性及其纤维成形两个方面综述了PHBV的研究进展。PHBV的物理改性主要有无机纳米粒子共混体系(PHBV/iNPs)、有机纳米晶共混体系(PHBV/oNPs)、高聚物共混体系(PHBV/Polymer)和绿色全降解共混体系;化学结构构筑主要包括接枝共聚改性、嵌段共聚改性、端基扩链改性等。从改性的手段及介质,分析了改性方法的优缺点。PHBV纤维的成形方法主要有熔融纺丝法、干法纺丝法及静电纺丝法。从PHBV纤维应用领域看,熔融纺纤维应用目标在于替代现有石油基相关产品,而静电纺纤维主要应用于开拓组织工程再生医学领域。最后,对PHBV今后的研究及发展提出了展望。     

聚乳酸耐热改性的研究进展

聚乳酸(PLA)是一种兼具良好生物相容性、力学以及加工性能的生物基可降解脂肪族聚酯,因此,在医药、食品包装等领域得到广泛应用。然而,PLA结晶速率慢、所得制品结晶度低、耐热性差,严重制约了其在高温环境下的使用。本文综述了国内外聚乳酸耐热改性方面的研究进展,重点阐述通过化学共聚、交联、共混以及外场作用(热处理、拉伸)等手段提高PLA耐热性的方法,并对耐热聚乳酸材料的发展前景进行了展望。     

超临界流体制备聚乳酸发泡材料的研究进展

石油基聚合物如聚苯乙烯等发泡材料因其质轻及优异的性能而受到广泛的应用.但是,石油基聚合物在自然环境条件下难以降解,存在"白色污染"的问题.因此,亟需开发绿色环境友好的聚合物发泡材料来代替石油基聚合物发泡材料.聚乳酸(PLA)是一种以可再生资源为原料的绿色高分子聚合物,因其具有完全生物可降解性,得到越来越多的关注.PLA...     

滑动接枝聚合物对聚乳酸的增韧改性

通过熔融共混的方法,在聚乳酸(PLA)中加入不同质量分数的滑动接枝聚合物(SGC),对其进行增韧改性。使用扫描电子显微镜(SEM)用来表征PLA和SGC共混物的相结构,冲击断裂样条断面SEM考察聚合物的增韧机理,差示扫描量热分析(DSC)和广角X-射线衍射(XRD)用来考察PLA以及PLA/SGC共混物的热性能和结晶性能。结果表明:PLA和SGC粒子呈现典型的"海-岛"结构,SGC粒子尺寸为0.8μm~4.1μm。含20%(wt)SGC的PLA/SGC共混物的断裂伸长率和缺口冲击强度较纯PLA分别提高了6倍和2倍,说明SGC能够有效地对PLA进行增韧改性。体外细胞毒性测试表明,PLA/SGC共混物的细胞毒性等级为1级,为无毒材料,因此可应用在生物医学领域。     

淀粉基高分子材料的研究进展

概述了近5年国内外在淀粉的化学、物理改性及其作为一种材料使用方面取得的最新研究进展.淀粉的化学改性主要介绍了淀粉的酯化、醚化、氧化、交联、接枝共聚等,而物理改性主要介绍了淀粉分别与黏土、脂肪族聚酯、聚乙烯醇以及纤维素等天然大分子的共混改性,同时还介绍了通过酸化制备淀粉纳米晶.淀粉基材料除了用于制备可生物降解塑料、吸附材...     

生物塑料--聚(β-羟基丁酸酯)的物理改性和化学改性

综述了生物塑料聚(β-羟基丁酸酯)(PHB)近年来在物理改性(共混改性)和化学改性(大分子反应改性和反应性共混改性)方面工作的进展状况。在PHB共混体系中,可解体性共混物和全生物降解性共混物是两类不同的共混体系,后者从长远意义上讲是解决环境污染问题的根本途径,而其现实意义上的用途是在生物医学领域。文章主要对PHB共混体系的相容性、热行为、结晶行为、机械性能和降解性能等方面的规律进行了总结。并指出反应性共混是较佳改善非相容PHB共混体系相容性的方法,而大单体反应改性和反应性共混则是改造PHB,提供新型功能化医用材料的有效手段。这些领域方面的研究代表了PHB改性工作新的发展方向。     

Polylactic acid (PLA) synthesis and modifications: a review

This article reviews various methods of synthesizing polycondensation and ring-opening polymerization and modifying properties of polylactic acid (PLA), which may be used as biomaterials, such as a drug carrier in a drug delivery system, as a cell scaffold and suture in tissue engineering, and as packaging materials in packaging engineering field. Copolymerization of lactide with other monomers or polymers such as malic acid, polyethylene glycol (PEG), polyglycolic acid (PGA), or dextran, as well as blending polylactide with natural derivatives and other methods of modification are discussed. Surface modifications of PLA-type copolymers, such as surface coating, chemical modification, and plasma treatment are described.     

Poly(Lactic Acid)-Based Graft Copolymers: Syntheses Strategies and Improvement of Properties for Biomedical and Environmentally Friendly Applications: A Review

As a potential replacement for petroleum-based plastics, biodegradable bio-based polymers such as poly(lactic acid) (PLA) have received much attention in recent years. PLA is a biodegradable polymer with major applications in packaging and medicine. Unfortunately, PLA is less flexible and has less impact resistance than petroleum-based plastics. To improve the mechanical properties of PLA, PLA-based blends are very often used, but the outcome does not meet expectations because of the non-compatibility of the polymer blends. From a chemical point of view, the use of graft copolymers as a compatibilizer with a PLA backbone bearing side chains is an interesting option for improving the compatibility of these blends, which remains challenging. This review article reports on the various graft copolymers based on a PLA backbone and their syntheses following two chemical strategies: the synthesis and polymerization of modified lactide or direct chemical post-polymerization modification of PLA. The main applications of these PLA graft copolymers in the environmental and biomedical fields are presented.     

直接法共聚改性聚乳酸研究新进展

聚乳酸(PLA)是一种重要的生物降解材料.广泛应用于生物医学、纤维、塑料等领域.为了改善PLA的性能,人们进行了大量的共聚改性研究.其中,直接从乳酸出发不经丙交酯中间体路线的共聚改性方法,因其简单易行、经济实用,越来越引起科学家的重视.针对直接法共聚改性聚乳酸物中物质种类的不同,结合本课题组的一些乳酸直接熔融共聚研究工...     

Sustainability assessments of bio-based polymers

Bio-based polymers have become feasible alternatives to traditional petroleum-based plastics. However, the factors that influence the sustainability of bio-based polymers are often unclear. This paper reviews published life cycle assessments (LCAs) and commonly used LCA databases that quantify the environmental sustainability of bio-based polymers and summarizes the range of findings reported within the literature. LCA is discussed as a means for quantifying environmental impacts for a product from its cradle, or raw materials extraction, to the grave, or end of life. The results of LCAs from existing databases as well as peer-reviewed literature allow for the comparison of environmental impacts. This review compares standard database results for three bio-based polymers, polylactic acid (PLA), polyhydroxyalkanoate (PHA), and thermoplastic starch (TPS) with five common petroleum derived polymers. The literature showed that biopolymers, coming out of a relatively new industry, exhibit similar impacts compared to petroleum-based plastics. The studies reviewed herein focused mainly on global warming potential (GWP) and fossil resource depletion while largely ignoring other environmental impacts, some of which result in environmental tradeoffs. The studies reviewed also varied greatly in the scope of their assessment. Studies that included the end of life (EOL) reported much higher GWP results than those that limited the scope to resin or granule production. Including EOL in the LCA provides more comprehensive results for biopolymers, but simultaneously introduces greater amounts of uncertainty and variability. Little life-cycle data is available on the impacts of different manners of disposal, thus it will be critical for future sustainability assessments of biopolymers to include accurate end of life impacts.     

Biopolymers for surface engineering of paper-based products

The combination of biopolymer science and technology with surface engineering of paper-based cellulosic materials has a lot of potential in stepping forward to a sustainable future. Various biopolymers such as oxidized starch, carboxymethyl cellulose, and polylatic acid have been commercially used to engineer paper surface. The paper-based cellulosic products are widely used for printing/writing and packaging applications. However, the production of these products are currently dependent mainly upon the use of petroleum-based materials including synthetic pigment coating latexes and barrier coating materials. The major challenges associated with some biopolymers are their relatively high costs and unsatisfactory performances. Continuing efforts are being made to enable the increased and value-added use of various biopolymers in paper surface engineering. These polymers can be based on cellulose, hemicelluloses, chitosan, alginate, protein, polylactic acid, and polyhydroxyalkanoate. The biopolymer-engineered paper products can be tailored for use as substitutes for various non-renewable materials including plastics and metals as well. Future development in the area of biopolymers for paper surface engineering is likely to lead to new possibilities and breakthroughs, paving the way for a substantially sustainable and green future.     

Modification of Polylactic Acid by Reactive Blending with Functionalized Imidazolium-based Ionomers and Epoxy-containing Additives北大核心CSCD

Aiming to tackle the serious brittleness problem of polylactic acid（PLA）,PLA-based multiphase blends are prepared by melting reactive blending with hydroxyl functionalized ionomer as the toughening agent and compatibilizer containing epoxy groups. The structures and properties of the blends are characterized by scanning electron microscopy（SEM）,Fourier transform infrared spectrometer（FT-IR）,differential scanning calorimetry（DSC）and mechanical properties tests. The synergistic compatibilization and toughening effects of epoxy soybean oil （ESO）,polyethylene glycol diglycidyl ether （PEGDE）and ethylene-methyl acrylate-glycidyl methacrylate （AX8900） terpolymer are compared and analyzed. The results show that the compatibilization effect is closely related to the content and position of the epoxy group in the additives,which presenting different toughening effects. The addition of AX8900 can effectively improve the toughness of the blend system to obtain balanced mechanical properties. However,ESO tends to lead to crosslinking,which limits the toughening efficiency. PEGDE mainly shows a plasticizing effect,leading to the reduction of tensile strength. The results demonstrate modification of the PLA blends by reactive blending with different epoxy additives and hydroxy-containing polymers is an effective strategy for the development of high-performance biobased PLA materials. © 2022, Science Press (China). All rights reserved.     

A Review of the Recent Developments in the Bioproduction of Polylactic Acid and Its Precursors Optically Pure Lactic Acids

Lactic acid (LA) is an important organic acid with broad industrial applications. Considered as an environmentally friendly alternative to petroleum-based plastic with a wide range of applications, polylactic acid has generated a great deal of interest and therefore the demand for optically pure l- or d-lactic acid has increased accordingly. Microbial fermentation is the industrial route for LA production. LA bacteria and certain genetic engineering bacteria are widely used for LA production. Although some fungi, such as Saccharomyces cerevisiae, are not natural LA producers, they have recently received increased attention for LA production because of their acid tolerance. The main challenge for LA bioproduction is the high cost of substrates. The development of LA production from cost-effective biomasses is a potential solution to reduce the cost of LA production. This review examined and discussed recent progress in optically pure l-lactic acid and optically pure d-lactic acid fermentation. The utilization of inexpensive substrates is also focused on. Additionally, for PLA production, a complete biological process by one-step fermentation from renewable resources is also currently being developed by metabolically engineered bacteria. We also summarize the strategies and procedures for metabolically engineering microorganisms producing PLA. In addition, there exists some challenges to efficiently produce PLA, therefore strategies to overcome these challenges through metabolic engineering combined with enzyme engineering are also discussed.     

The Impact of Filler Geometry on Polylactic Acid-Based Sustainable Polymer Composites

Recently, biocomposites have emerged as materials of great interest to the scientists and industry around the globe. Among various polymers, polylactic acid (PLA) is a popular matrix material with high potential for advanced applications. Various particulate materials and nanoparticles have been used as the filler in PLA based matrix. One of the extensively studied filler is cellulose. However, cellulose fibres, due to their hydrophilic nature, are difficult to blend with a hydrophobic polymer matrix. This leads to agglomeration and creates voids, reducing the mechanical strength of the resulting composite. Moreover, the role of the various forms of pure cellulose and its particle shape factors has not been analyzed in most of the current literature. Therefore, in this work, materials of various shapes and shape factors were selected as fillers for the production of polymer composites using Polylactic acid as a matrix to fill this knowledge gap. In particular, pure cellulose fibres (three types with different elongation coefficient) and two mineral nanocomponents: precipitated calcium carbonate and montmorillonite were used. The composites were prepared by a melt blending process using two different levels of fillers: 5% and 30%. Then, the analysis of their thermomechanical and physico-chemical properties was carried out. The obtained results were presented graphically and discussed in terms of their shape and degree of filling.     

Molecular structure regulation of functional polylactic acid based on chain expansion reaction and its improved hydrolysis resistance

In this work, the functional polylactic acid (PLA) was synthesized using epoxy chain extender (ADR) as a chain extender agent through melt blending method. The effects of ADR content on the molecular structure, thermal properties, and tensile properties of the functional PLA were investigated. Meanwhile, the hydrolytic behavior of the PLA/ADR materials at different hydrolysis temperatures was explored. It was found that ADR effectively regulated the molecular structure of PLA in the molten state and significantly increased the relative molecular weight, storage modulus, and complex viscosity of PLA. In addition, the Cole-Cole diagram results suggested the branched structure of PLA chain expansion systems. Based on mechanical property tests, it was noted that the addition of ADR made the molecular chain form a micro-crosslinked structure. Additionally, the mass loss rate of PLA/1.6ADR (the dosage of ADR was 1.6 wt%) was 14.75% after 14 weeks of hydrolysis under hydrolysis conditions at 58°C, while that of pure PLA was 25.89%. Moreover, the functional PLA/ADR materials exhibited significantly slower decrease rates in molecular weight, melting temperature, and tensile strength, and still maintained intact morphology after 14 weeks of hydrolysis compared to pure PLA. Therefore, the molecular structure of PLA is effectively regulated by ADR, which greatly enhances the hydrolysis resistance and further promotes the range of application of PLA.     

Biodegradability study of polylactic acid/ thermoplastic polyurethane blends

Blends with varied ratio of polylactic acid (PLA) and thermoplastic polyurethane (TPU) were prepared by melt blending. The PLA content in blends was 20, 40, 60 and 80 wt%. Samples of pure PLA and TPU that underwent the same thermal treatment were also prepared. Biodegradation was examined by respirometry. Pure TPU started to degrade immediately due to degradation of the low molecular weight plasticizer in the polymer. Pure PLA, on the other hand, exhibited an incubation period after which degradation progressed rapidly and was almost complete after 70 days. The degradation profile of the blends can be correlated to their morphology. Samples with a co-continuous morphology initially degrade at a higher rate than the rest of the samples due to the higher exposure of the TPU phase in these blends.