聚乳酸改性的研究进展

综述了聚乳酸化学、物理以及纳米复合改性方面的研究进展,重点讨论了目前的研究热点及其今后的发展趋势,并时其前景做了展望.     

FEP纤维的等离子体表面改性

以空气气氛对聚全氟乙丙烯（FEP）纤维进行等离子体处理,利用SEM、DSC、XPS对改性前后纤维的性能及形貌进行表征,并测试水在纤维表面的接触角。等离子体处理后纤维的表面发生了C—F键断裂,表面形貌变得粗糙,O原子含量增加4.65%,F原子含量降低4.37%,O/C、F/C原子含量比分别由0.19和0.28变为0.25和0.22,但DSC结果表明结晶度未发生变化;水在纤维表面的接触角由改性前的112.3°降至改性后的54.1°,纤维亲水性得到明显增强。     

Plasma surface modification of advanced organic fibres

A marked improvement in the interlaminar shear strength and flexural strength of aramid/ epoxy composites is observed when the fibres are pretreated in an ammonia or ammonia/ nitrogen gaseous discharge (plasma) to introduce amine groups on to the fibre surface. Scanning electron and optical microscopic observations are used to examine the microscopic basis for these results. Scanning electron micrographs of shear fracture surfaces show clean fibre/matrix separation in composites made from untreated fibres, indicative of weak interfacial bonding. In contrast, shear fracture surfaces of composites containing plasma-treated fibres exhibit clear evidence of fibre fibrillation and matrix cracking, suggesting stronger interfacial bonding. Optical microscopic examination of flexure specimens shows that enhanced strength results mainly from reduced compressive fibre buckling and debonding, due to an increase in fibre/matrix interfacial bond strength. This increase is not accompanied by any significant change in the interlaminar fracture energy or flexural modulus of the composites, but there is an appreciable loss in transverse ballistic impact properties. These results are also examined in terms of the observed increase in fibre/matrix interfacial strength.     

Plasma surface modification of advanced organic fibres

The interlaminar shear strength, interlaminar fracture energy, flexural strength and modulus of extended-chain polyethylene/epoxy composites are improved substantially when the fibres are pretreated in an ammonia plasma to introduce amine groups on to the fibre surface. These property changes are examined in terms of the microscopic properties of the fibre/matrix interface. Fracture surface micrographs show clean interfacial tensile and shear fracture in composites made from untreated fibres, indicative of a weak interfacial bond. In contrast, fracture surfaces of composites made from ammonia plasma-treated fibres exhibit fibre fibrillation and internal shear failure as well as matrix cracking, suggesting stronger fibre/matrix bonding, in accord with the observed increase in interlaminar fracture energy and shear strength. Failure of flexural test specimens occurs exclusively in compression, and the enhanced flexural strength and modulus of composites containing plasma-treated fibres result mainly from reduced compressive fibre buckling and debonding due to stronger interfacial bonding. Fibre treatment by ammonia plasma also causes an appreciable loss in the transverse ballistic impact properties of the composite, in accord with a higher fibre/matrix interfacial bond strength.     

Plasma surface modification of advanced organic fibres

Aramid and extended-chain polyethylene fibres have been treated in ammonia and oxygen plasmas in order to enhance adhesion to vinylester resins and thereby improve fibre/resin interfacial properties in composites made from these materials. For both aramid/vinylester and extended-chain polyethylene/vinylester composites, the plasma treatments result in significant improvements in interlaminar shear strength and flexural strength. Extended-chain polyethylene/vinylester composites also exhibit increased flexural modulus. Scanning electron and optical microscopic observations have been used to examine the microscopic basis for these results, which are compared with results previously obtained for aramid/epoxy and extended-chain polyethylene/epoxy composites. It is concluded that the increased interlaminar shear and flexural properties of vinylester matrix composites are due to improved wetting of the surface-treated fibres by the vinylester resin, rather than covalent chemical bonding.     

苎麻织物表面改性对其增强热固性聚乳酸复合材料力学及阻燃性能的影响

采用碱处理、硅烷偶联剂处理、碱+硅烷偶联剂复合处理、碱+阻燃剂+硅烷偶联剂复合处理对苎麻织物进行表面改性,采用模压工艺制备了苎麻织物增强热固性聚乳酸(PLA)复合材料。研究了4种表面改性方法对苎麻织物/PLA复合材料弯曲性能的影响,采用SEM研究了苎麻纤维与PLA基体之间的界面结合状况。结果表明:经过4种表面改性处理后苎麻织物/PLA复合材料的弯曲性能均有所提高,其中碱+硅烷偶联剂复合处理后提高幅度最大,苎麻织物/PLA复合材料的弯曲强度、模量分别提高了59.5%、51.9%。碱+阻燃剂+硅烷偶联剂复合处理后苎麻织物/PLA复合材料的弯曲强度、模量较未处理时分别提高了38.0%、66.8%;且苎麻织物/PLA复合材料60s点火时间的损毁长度为8.25cm,达到了美国DOT/FAA/AR-00/12要求的标准。SEM结果表明:改性处理后苎麻织物/PLA复合材料中纤维与树脂之间的界面结合更好。     

PBO纤维表面等离子体接枝改性研究

采用等离子体接枝改性方法对PBO纤维表面进行改性研究，利用AFM分析改性前后纤维表面的形貌变化，测试了改性前后纤维表面浸润性变化，并采用Microbond方法表征了纤维与树脂基体的界面IFSS。结果表明：等离子体接枝后纤维表面引入了活性基团，纤维浸润性改善；在100W、10min接枝条件下IFSS提高了75％。     

Plasma surface treatment and modification of glass fibers

New helical coupling plasma system for continuous surface treatment and modification (surface processing) of fiber bundles has been developed and tested for glass fibers. The system enables surface processing of single filaments and flat substrates as well. Surface processed glass fibers and their bundles were examined as reinforcements for glass fiber/polyester composite systems. Processing of fibers comprised a surface treatment using argon gas and a surface modification using hexamethyldisiloxane and vinyltriethoxysilane monomers. Interfacial and interlaminar shear strengths of plasma processed glass fiber/polyester systems were compared with those of untreated and commercially sized fibers.     

聚乳酸的直接缩聚、改性及应用研究现状

阐述了聚乳酸的直接缩聚法合成工艺,论述了聚乳酸的改性方法包括:共聚、交联、表面改性、共混、增塑、复合以及一些新技术,综述了聚乳酸在生物医用领域及塑料纤维领域的应用进展。     

How to improve mechanical properties of polylactic acid with bamboo fibers

Bamboo fibers (BF) were mixed in polylactic acid (PLA) to improve its mechanical properties: impact strength and heat resistance. Three different types of BF were extracted from raw bamboo by either sodium hydroxide (NaOH) treatment or steam explosion in conjunction with mechanical processing. They were designated as “short fiber bundle,” “alkali-treated filament” and “steam-exploded filament,” respectively. Composite samples were fabricated by injection molding using PLA/BF pellets prepared by a twin-screw extruding machine. Among them, the highest bending strength was obtained when steam-exploded filaments were put into PLA matrix. Impact strength of PLA was not greatly improved by addition of short fiber bundles as well as both filaments. In order to improve the impact strength of PLA/BF composites, PLA composite samples were alternatively fabricated by hot pressing using medium length bamboo fiber bundles (MFB) to avoid the decrease in fiber length at fabrication. Impact strength of PLA/MFB composite significantly increased, in which long fiber bundles were pulled out from the matrix. The addition of BF improves thermal properties and heat resistance of PLA/BF composites due to the constraint of deformation of PLA in conjunction with crystallinity promoted by anneal (at 110 °C for 5 h).     

Plasma transferred arc surface modification of a low carbon steel

The potential of Plasma Transferred Arc (PTA) hardfacing goes beyond the surface welding of superalloys. This work evaluated low carbon steel surface modification by PTA deposition of fine WCoC carbides, and mixtures of Fe powders and 5–35 wt% carbides. Characterization included visual inspection, optical and scanning electron microscopy, X-ray diffraction and microhardness profiles. PTA processing allowed for the dissolution of carbides confirmed by X-ray diffraction, leading to homogeneous microstructures. Microstructures varied from a Widmanstätten morphology to a typical dendritic solidification structure upon the WCoC content. Surface soundness depended on powder preparation and composition. Sound surfaces exhibiting hardness up to 700 Hv were obtained for the 35 wt% WCoC powder mixture.     

Formation of a nano-pattering NiTi surface with Ni-depleted superficial layer to promote corrosion resistance and endothelial cell-material interaction

Zirconium ion implantation was performed on NiTi alloy to suppress Ni ion release as well as to improve corrosion resistance and cell-material interaction. A thicker Ni-depleted nano-scale composite layer formed after Zr implantation and the corrosion resistance was evidently increased in aspects of increased E _br ? E _corr (difference between corrosion potential and breakdown potential) and decreased corrosion current density. 2.5/2 NiTi sample possessed the highest E _br ? E _corr, more than 500 mV higher than that of untreated NiTi, suggesting a significant improvement on pitting corrosion resistance. Ni ion release rate of Zr–NiTi was decreased due to the depletion of Ni in the superficial surface layer and the diffusion resistance effect of the ZrO₂/TiO₂ nano-film. Increased surface wettability induced by increased surface roughness was obtained after Zr implantation. Zr–NiTi samples were found to be favorable to endothelial cells (ECs) proliferation, especially after 5 and 7 days culture.     

Surface modification of polylactic acid by ion,electron beams and low-temperature plasma: a review

Journal of Materials Science - We review the work that has been done on the modification of polylactic acid by irradiation methods including low-temperature plasma treatment, electron-beam...     

硬脂酸对纳米TiO2有机表面修饰方法的研究

报道了一种利用硬脂酸对纳米TiO2进行有机表面修饰的新方法,主要包括纳米TiO2水分散液的制备和把纳米TiO2粒子由水分散液中转移到溶有硬脂酸的甲苯溶液中两个过程.采用红外光谱(FT-IR)、X射线光电子能谱(XPS)、热分析(TG-DTA)、透射电镜(TEM)、粒度分布、紫外-可见光谱和分散性实验等对所得的样品进行了...     

Surface modification of poly-L-lactic acid films by electrostatic self-assembly to promote vascular smooth muscle cells growth

The intention of this study was to surface modify the poly-L-lactic acid (PLLA) film and evaluate the effects of the surfaces on the growth of vascular smooth muscle cells (VSMCs) in vitro. Collagen and hyaluronic acid (HA) were utilized as polycation and polyanion in this study. Layer-by-layer (LBL) self-assembly technique was used to lead to the formation of multilayer moleculer on the poly-L-lactic acid (PLLA) film surfaces. Collagen/HA layers was overcasted coating on the PLLA surface after the activation layers by poly-(ethyleneimine) (PEI). The structure and morphology of the multilayer molecular were examined by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrophotometer and atomic force microscope (AFM), respectively. The ATR-FTIR analysis illuminated the presence of collagen on the PLLA surface. The AFM results showed the multilayer appeared on PLLA surface. The VSMCs were adopted to evaluate the cyto-compatibility of the modified PLLA films. It was found that the viability of VSMCs on the modified PLLA films were greater than that on original PLLA films and tissue culture plastic after ten days culture (p < 0.05). Scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM) data also confirmed the homogeneous results. These data suggest that collagen/HA coat can be successfully adopted in the surface modification of PLLA film through LBL technique, and also can enhance its cell compatibility.     

聚乳酸的降解研究

探讨了聚乳酸水解以及超声波降解情况,利用傅立叶红外光谱(FT-IR)和凝胶渗透色谱仪测定其基团及相对分子质量变化。研究结果表明:聚乳酸超声波降解同其水解均为酯键断裂导致的,并且是酯键的任意断裂,在水解过程中聚乳酸质量损失快慢为盐酸溶液>磷酸缓冲液>去离子水;聚乳酸在水解过程中,相对分子量随降解时间的延长而减小,但在超声波作用30min下其质量有一定程度的损失而相对分子量反而增大,推断其可能发生了部分交联反应。     

纳米氧化锌硬脂酸改性工艺研究

用硬脂酸作改性剂,对其改性纳米氧化锌的工艺条件进行了研究,并给出了适合工业化生产的最佳工艺条件。     

聚己二酸丙三醇酯增韧改性聚乳酸的研究

以丙三醇(G)、己二酸(A)为原料,制备了一种新型聚乳酸(PLA)增韧改性剂--聚己二酸丙三醇酯(PGA).通过熔融共混的方法制备了PGA/PLA共混物,并*利用偏光显微镜(PoM)、动态力学分析(DMA)等对其动态热机械性能、冲击强度及相态结构进行了表征.研究结果表明,PGA的加入改善了PLA材料的柔性,PGA含量为15%的PGA/PLA共混物的冲击强度达到48.0J/m,比纯PLA提高了300.0%.     

Surface modification of a porous hydroxyapatite to promote bonded polymer coatings

Porous hydroxyapatite (Hap) blocks were sintered at several temperatures and methyl methacrylate (MMA) grafted onto the surface in a 2-step heterogeneous system as a model example for surface modification. First, sintered porous Hap was modified with 2-methacryloyloxyethylene isocyanate (MOI) monomer in anhydrous dimethyl sulfoxide using di-n-butyltin (IV) dilaurate as a catalyst and hydroquinone as an inhibitor. Amount of the introduction of MOI monomer on porous Hap was 1.62 wt % at sintered temperature 800 °C, 0.68 wt % at it of 1000 °C, and 0.59 wt % at it of 1200 °C. Scanning electron microscopy (SEM) showed that porous Hap pore size and shape before and after MOI treatment were unchanged. Second, graft polymerization with MMA through the vinyl bond on porous Hap was conducted using ,-azobis isobutyronitrile (AIBN) as an initiator. Amount of Grafted PMMA on the MOI modified porous Hap was 2.84 wt % at sintered temperature of 800 °C, 6.97 wt % at it of 1000 °C, and 6.27 wt % at it of 1200 °C. MOI-modified and PMMA-grafted porous Hap were characterized using Fourier transform infrared (FT-IR) spectroscopy. The compressive strength of sintered porous Hap with grafted PMMA increased about 2.7–6.7 times compared to intact porous Hap. This 2-step surface modification on porous Hap is widely applicable to graft polymerization with vinyl polymer and conjugation with a protein or an oligopeptide, such as growth factor or an adhesion molecule, to improve Hap mechanical properties and functionality.     

A new growth factor controlled drug release system to promote healing of bone fractures: nanospheres of recombinant human bone morphogenetic-2 and polylactic acid

To prepare a new drug control release system, which can markedly promote the healing of bone fractures. Optimized water-in-oil-in-water multiple emulsion evaporation method, prepared nanospheres of recombinant human bone morphogenetic-2 and polylactic acid (rhBMP-2-PLA-Ns). Its physical character was determined by the enzyme linked immunosorbent assay method. Its bioactivity was measured with the microculture tetrazolium test immunohistochemical analyses, alizarin red staining and western blot analysis. rhBMP-2-PLA-Ns exhibited an even and uniform spherical appearance without adhesion, with a particle size distribution between 35 and 65 nm, and a mean size of 45 nm. The drug loading volume and encapsulation efficiency reached ([124.73 +/- 0.41] x 10(-3))% and (90.54 +/- 1.32)%, respectively. The drug release in vitro persisted for 14 days, with a mean concentration of 73.44 +/- 5.38 ng/ml, and corresponded to the Higuichi equation (r = 0.9962). The microculture tetrazolium test showed that 4 days later, the optical density value ranking was rhBMP-2-PLA-N group > rhBMP-2 group > blank control group. Fluorescence immunocytochemical analysis showed that 10 days later the fluorescent density of the rhBMP-2-PLA-N group was significantly higher than the other two groups. Western blot analysis confirmed that the amount of vascular endothelial growth factor in the rhBMP-2-PLA-N group was the greatest. This study showed that rhBMP-2-PLA-Ns have excellent biological activity, can promote proliferation, differentiation and mineralization of osteoblasts. The drug release time is suitable for fracture healing and is an ideal delivery system for fracture healing.