聚乳酸及其复合材料降解的研究进展

聚乳酸(PLA)是良好的生物可降解塑料,但因聚乳酸材料价格高、脆性大、抗降解性较差而限制了其在工业上的大规模应用。制备聚乳酸基复合材料是克服聚乳酸缺点的一种有效方法,因而,近年来得到了人们的普遍研究。随着研究成果的不断完善,聚乳酸复合材料的污染又成了一个新的问题。文章综述了聚乳酸基复合材料国内外的各种降解方法及研究进展。纯聚乳酸材料在自然界中的降解速率缓慢,不利于材料报废后的降解处理。添加各种填料制成聚乳酸复合材料后,会对聚乳酸基复合材料的降解速率产生一定的影响。文章通过分析聚乳酸复合材料降解速率的可控性,综述了国内外各种聚乳酸基复合材料的降解方法及研究进展。     

聚乳酸类材料的水解特性

聚乳酸具有良好的生物降解性、生物相容性和生物可吸收性,研究其在水中的降解行为对于指导聚乳酸的改性,满足不同的实际需要有非常重要的意义.本文对聚乳酸类降解材料的水解机理、影响水解的因素进行了综述.     

生物可降解材料——聚乳酸的研究进展

聚乳酸具有良好的生物相容性、降解性和可吸收性,已经广泛用于医药包覆、缓释药物、手术缝合线、骨折固定材料。综述了聚乳酸的主要合成方法,以及通过与其它材料的复合,改进聚乳酸的结构及性能,以进一步扩大应用范围。     

生物降解医用材料的制备及应用研究

介绍了生物降解医用材料的特性及降解机理,典型生物医用材料聚乳酸、壳聚糖的制备及生物降解医用材料在临床医学及药学领域的主要应用.     

PLA热稳定性和降解性能研究及其应用

综述了聚乳酸的种类、性能、热稳定性和降解性能的研究及其应用。聚乳酸具有良好的生物降解性和生物相容性,是一种环境友好型高分子材料。聚乳酸因其热稳定性较差,需要进行改性处理,从共混、共聚、添加剂和加工工艺4个方面进行改性处理都可以改善聚乳酸的热稳定性。     

聚乳酸/羟基磷灰石复合材料研究进展

综述了近年聚乳酸/羟基磷灰石复合材料的制备及改性方法,包括溶液共混法、熔融共混法和原位共聚法等。同时对聚乳酸/羟基磷灰石复合材料在人工骨修复以及生物固定支撑材料等领域的应用前景进行了展望。聚乳酸/羟基磷灰石复合材料的高性能化和降解速率可控将是新一代聚乳酸/羟基磷灰石复合材料的追求目标。     

聚乳酸/羟基磷灰石复合材料研究进展

综述了近年聚乳酸/羟基磷灰石复合材料的制备及改性方法,包括溶液共混法、熔融共混法和原位共聚法等。同时对聚乳酸/羟基磷灰石复合材料在人工骨修复以及生物固定支撑材料等领域的应用前景进行了展望。聚乳酸/羟基磷灰石复合材料的高性能化和降解速率可控将是新一代聚乳酸/羟基磷灰石复合材料的追求目标。     

碳纤维增强聚乳酸复合材料的研究进展

介绍了以碳纤维为增强纤维、聚乳酸为基体,采取相应的加工工艺制备出碳纤维增强聚乳酸复合材料的种类与制备工艺,研究了该复合材料的相关性能,发现该材料与聚乳酸材料相比力学性能、抗冲击性能得到了明显改善,有一定的降解性,并且生物相容性良好,适合于开发骨折内固定材料、骨修复材料等.概述了碳纤维增强聚乳酸复合材料在工业化生产及应用中存在的主要问题,并对今后的应用研究进行了展望.     

低聚物对左旋聚乳酸水解性能的影响

左旋聚乳酸(PLLA)在可植入生物全降解材料中具有极其重要的地位。然而,在对力学强度有一定要求的条件下降解速度慢的问题始终存在。为了探究促进左旋聚乳酸降解的方法,采用溶液共混和热压成型的方式制备了左旋聚乳酸与左旋乳酸低聚物的混合物。并进一步对其力学、热力学、质量损失和降解速率进行了研究。结果表明,加入适量的低聚物可以保持较高的力学强度;共混后结晶峰值温度(T_c)、玻璃化转变温度(T_g)降低、无相分离出现,说明低聚物共混有很好的相容性;质量损失表明,低聚物能加快左旋聚乳酸降解;降解速率模型分析表明,5%低聚物含量的共混物可以实现左旋聚乳酸3倍的降解速率。     

稀土耐热改性剂让聚乳酸性能“升级”

聚乳酸是一种可生物降解材料。玉米、秸秆、稻壳等植物资源所提炼出的淀粉物质都可以成为制造聚乳酸的原料,而聚乳酸具有良好的生物可降解性,使用后能被自然界中微生物完全降解,其生成产物为二氧化碳和水,对环境没有污染,是公认的环境友好材料。虽然聚乳酸的应用领域非常广阔,但是具有韧性差、热稳定性差、断裂伸长率小、基体较脆等缺点,并且由于技术成熟度低,生产成本高也制约着聚乳酸的扩大应用。如何解决这些问题将成为推动聚乳酸材料发展的攻坚点,包头稀土研究院将稀土改性剂作为了突破口。     

高密度聚乙烯复合薄膜生物降解性的研究

将聚乳酸、淀粉分别与高密度聚乙烯(HDPE)共混,制备了具有一定降解性能的HDPE塑料薄膜。研究了聚乳酸和淀粉对HDPE薄膜力学性能、降解性能、降解后的力学性能、结晶、微观结构等的影响。结果表明:聚乳酸和淀粉能提高HDPE薄膜的力学性能,复合薄膜降解30d后力学性能会有一定程度的降低。     

生物降解材料在水环境中降解性能的研究进展

综述了目前典型生物降解材料在水环境中降解性能的研究现状,详细介绍了聚乳酸（PLA）高分子材料（PLA、PLA共聚物、PLA复合材料等）、聚羟基烷酸酯（PHA）、聚己内酯（PCL）、聚丁二酸丁二醇酯（PBS）、聚（己二酸丁二醇酯?对苯二甲酸乙二醇酯）（PBAT）和CO₂共聚物等在不同水环境中的降解性能;最后总结了生物降解材料未来需要关注的问题和发展方向。     

生物降解材料聚乳酸及其共聚物的降解研究

论述了聚乳酸(PLA)的基本性质、降解过程、降解机理,综述了国内外PLA降解方法的研究进展,探讨了降解的影响因素,并展望了PLA的开发和应用前景.     

Poly(lactic acid)/carbon nanotube nanocomposites with integrated degradation sensing

For the first time, an in-situ degradation monitoring system for biodegradable polymers is reported in present work. The proposed concept is based on a conductive biodegradable polymer composite, where carbon nanotubes (CNTs) are incorporated in poly(lactic acid) (PLA) in order to develop an intelligent biocomposite system that can sense biodegradation. Changes in electrical resistivity of the PLA/CNT nanocomposites were successfully correlated with degradation levels of the biopolymer. PLA/CNT nanocomposites demonstrated excellent degradation sensing abilities at CNT concentrations around the percolation threshold, with resistivity changes of about four orders of magnitude with biodegradation. In contrast to many other stimuli, biodegradation resulted in a reduction in resistivity due to an increased CNT network density after partial removal of the amorphous phase of the polymer matrix.     

A review on degradation mechanisms of polylactic acid: Hydrolytic,photodegradative, microbial,and enzymatic degradation

Recently, thoughtful disagreements between scientists concerning environmental issues including the use of renewable materials have enhanced universal awareness of the use of biodegradable materials. Polylactic acid (PLA) is one of the most promising biodegradable materials for commercially replacing nondegradable materials such as polyethylene terephthalate and polystyrene. The main advantages of PLA production over the conventional plastic materials is PLA can be produced from renewable resources such as corn or other carbohydrate sources. Besides, PLA provides adequate energy saving by consuming CO₂ during production. Thus, we aim to highlight recent research involving the investigation of properties of PLA, its applications and the four types of potential PLA degradation mechanisms. In the first part of the article, a brief discussion of the problems surrounding use of conventional plastic is provided and examples of biodegradable polymers currently used are provided. Next, properties of PLA, and (Poly[L-lactide]), (Poly[D-lactide]) (PDLA) and (Poly[DL-lactide]) and application of PLA in various industries such as in packaging, transportation, agriculture and the biomedical, textile and electronic industry are described. Behaviors of PLA subjected to hydrolytic, photodegradative, microbial and enzymatic degradation mechanisms are discussed in detail in the latter portion of the article.     

Influence of blocked polyisocyanate on thermomechanical, shape memory and biodegradable properties of poly(lactic acid)/poly(ethylene glycol) blends

A series of shape memory biodegradable blends from poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) were prepared by solution casting method. Ethyl cellosolve-blocked polyisocyanate (EC-bp) was synthesized and used as a cross-linker to obtain cross-linked PLA/PEG blends. The chemical structure of the prepared composite was confirmed by Fourier transform infrared spectra. Thermomechanical, thermal and shape memory properties of the blends were investigated and compared by dynamic mechanical analysis, thermogravimetric analysis and shape memory testing. The results showed that EC-bp cross-linked PLA/PEG blends had better thermal and thermomechanical properties than non-cross-linked blends and displayed good shape memory effects in both shape fixity rate and shape recovery rate. Moreover, the effect of EC-bp addition on the rate of biodegradable degradation in a phosphate buffer solution (pH 7.4) was studied at 37?°C. The prepared cross-linked PLA/PEG blends demonstrated better degradation resistance compared to the non-cross-linked blends.     

Novel Biodegradable 3D-Printed Analgesics-Eluting-Nanofibers Incorporated Nuss Bars for Therapy of Pectus Excavatum

A novel hybrid biodegradable Nuss bar model was developed to surgically correct the pectus excavatum and reduce the associated pain during treatment. The scheme consisted of a three-dimensional (3D) printed biodegradable polylactide (PLA) Nuss bar as the surgical implant and electrospun polylactide–polyglycolide (PLGA) nanofibers loaded with lidocaine and ketorolac as the analgesic agents. The degradation rate and mechanical properties of the PLA Nuss bars were characterized after submersion in a buffered mixture for different time periods. In addition, the in vivo biocompatibility of the integrated PLA Nuss bars/analgesic-loaded PLGA nanofibers was assessed using a rabbit chest wall model. The outcomes of this work suggest that integration of PLA Nuss bar and PLGA/analgesic nanofibers could successfully enhance the results of pectus excavatum treatment in the animal model. The histological analysis also demonstrated good biocompatibility of the PLA Nuss bars with animal tissues. Eventually, the 3D printed biodegradable Nuss bars may have a potential role in pectus excavatum treatment in humans.     

Maleic Anhydride-Grafted PLA Preparation and Characteristics of Compatibilized PLA/PBSeT Blend Films

Poly(butylene sebacate-co-terephthalate) (PBSeT) is a biodegradable flexible polymer suitable for melt blending with other biodegradable polymers. Melt blending with a compatibilizer is a common strategy for increasing miscibility between polymers. In this study, PBSeT polyester was synthesized, and poly(lactic acid) (PLA) was blended with 25 wt% PBSeT by melt processing with 3–6 phr PLA-grafted maleic anhydride (PLA-g-MAH) compatibilizers. PLA-g-MAH enhanced the interfacial adhesion of the PLA/PBSeT blend, and their mechanical and morphological properties confirmed that the miscibility also increased. Adding more than 6 phr of PLA-g-MAH significantly improved the mechanical properties and accelerated the cold crystallization of the PLA/PBSeT blends. Furthermore, the thermal stabilities of the blends with PLA-g-MAH were slightly enhanced. PLA/PBSeT blends with and without PLA-g-MAH were not significantly different after 120 h, whereas all blends showed a more facilitated hydrolytic degradation rate than neat PLA. These findings indicate that PLA-g-MAH effectively improves PLA/PBSeT compatibility and can be applied in the packaging industry.     

Melt-spun poly(lactic acid) fibers modified with soy fillers: Toward environment-friendly disposable nonwovens

Poly(lactic acid) (PLA) has a significant potential as a biodegradable polymer, but its high cost and slow biodegradability restrict its use in disposable products. This study establishes a novel route to accomplish both objectives by the addition of low-cost soy fillers into PLA, which reduced material cost and increased the degradation rate of resulting soy-PLA fibers. Due to partial thermal degradation of soy fillers at PLA melt temperature, they could be melt-compounded into PLA up to 5 wt%. Fine continuous fibers (D ∼ 25-50 μm) were successfully produced via melt spinning, and further melt-consolidated into prototypical nonwovens. The tensile strength of soy-PLA fibers containing soy reside and soy flour were 56 ± 9 and 44 ± 5 MPa, respectively. Although slightly lower than that of neat PLA fibers (74 ± 2 MPa), the fibers possessed adequate tenacity for use as nonwoven fabrics. Fiber modulus remained unaffected at about 2.5 GPa. The soy-PLA fibers displayed a relatively rough exterior surface and provided a natural-fiber feel. The overall degradation of soy-PLA fibers was accelerated about 2-fold in a basic medium due to the preferential dissolution of soy that led to increased surface area within the PLA matrix indicating their potential for use in biodegradable nonwovens.     

Poly(lactic acid)/polystyrene bioblends characterized by thermogravimetric analysis,differential scanning calorimetry,and photoacoustic infrared spectroscopy

Bioblends are composites of at least one biodegradable polymer with nonbiodegradable polymer. Successful development of bioblends requires that the biodegradable polymers be compatible with other component polymers. Compatibility can be assessed by evaluating the intermolecular interactions between the component polymers. In this work, the interaction in binary bioblends comprising biodegradable poly(lactic acid) (PLA) and polystyrene (PS) was investigated using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared photoacoustic spectroscopy (FTIR‐PAS). The TGA studies indicated that incorporation of PLA in PS resulted in thermal destabilization of PS. The DSC studies showed that some parameters favored partial miscibility of PS in PLA, while others favored immiscibility, such as the existence of two glass transitions. The FTIR‐PAS spectra revealed the presence of intermolecular n–π interactions between PLA and PS and indicated that the degree of interaction was dependent on the concentrations of the polymers in the bioblends. FTIR‐PAS results computed via differential spectral deconvolution were consistent with, and therefore support, the results of TGA and DSC analyses of PLA/PS bioblends. The degradation kinetics, used to determine the degradation mechanism, revealed a two‐ or three‐step mechanism. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007