原位缩聚合成含聚芳酰胺／酯的微相复合物 Ⅴ．共聚酰胺与聚砜的微相复合物制备

用原位缩聚法合成了芳香-脂肪共聚酰胺与聚砜的徽相复合物(PAA／PSF)。初步结果表明:PAA／PSF微相复合物具有热致液晶性能;PAA的加入大大提高了微相复合物的力学性能。以PA30(PAA=29．5ω)为例,拉伸强度和模量分别提高到原来的2．5倍和3．5倍。     

原位缩聚合成含聚芳酰胺/酯的微相复合材料 Ⅳ.全芳香聚酰胺与聚砜的微相复合材料制备

以原位缩聚方法合成了PPTA/PSF的微相复合材料。FTIR、DSC等分析结果表明,PPTA/PSF微相复合材料较PPTA/PBT-PTMG分子链间存在着更强的相互作用,PPTA对基体聚合物的力学性能有较大的提高。初步结果表明,加入第三单体双酚A在一定程度上提高了复合材料的抗张强度和断裂伸长率,但是模量有所下降。     

明胶/羟基磷灰石复合物微球中明胶对无机相影响的研究

在油包水的乳液体系中,通过原位合成的方法使羟基磷灰石(HAP)在明胶链上化学沉积,改变明胶溶液的浓度,制得了一系列的明胶/HAP复合物微球.采用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和热失重分析仪(TGA)等对产物的组成、形貌以及热失重情况进行了表征.结果表明,明胶用量对复合物微球中HAP的形成具有重要影响.在明胶溶液浓度为0.025 g/mL时,明胶分子链提供的结合位点恰好与溶液中游离的Ca2+、PO43-等离子达到平衡状态,复合物微球中无机相含量达40%,这是明胶与HAP以化学键合的形式结合所能得到的最大值.     

溶剂的溶胀与乙基氰乙基纤维素胆甾相结构变化

乙基氰乙基纤维素 [(E -CE)C]/聚丙烯酸 [PAA]分子复合物通过用光引发聚合乙基氰乙基纤维素 /丙烯酸胆甾型液晶溶液中的丙烯酸得到。在 (E -CE)C/PAA分子复合物中 ,PAA在水中的溶胀影响到胆甾型液晶相结构。胆甾型液晶相选择性反射光的波长随着PAA的溶胀向长波方向位移。同时还发现 ,在PAA溶胀过程中胆甾型液晶相的螺距增加 ,取向分子层之间的距离减小。     

沙棘枝条粉/PAA超强吸水复合物的制备及性能研究

以废弃沙棘枝条粉(HBP)为基体,丙烯酸(AA)为单体,过硫酸钾(K2S2O8)为引发剂,N,N'-亚甲基双丙烯酰胺(MBA)为交联剂,采用自由基溶液聚合法制备HBP/PAA(聚丙烯酸)超强吸水复合物。用红外光谱和场发射电子扫描电镜表征所制备的HBP/PAA。HBP/PAA超强吸水复合物在去离子水和0.9%Na Cl溶液的吸水倍率分别可达190.0 g/g和40.0 g/g。该复合物具有良好的保水性和反复吸放液性能。     

原位缩聚合成含聚芳酰胺／酯的微相复合物 Ⅲ．全芳聚酰胺与聚酯-聚醚体系的研究

对于聚对苯二甲酰对苯二胺(PPTA)和PBT-PTMG体系,比较了溶剂配比(CH2Cl2／NMP)、聚合物浓度、强极性溶剂的用量和加料方式对缩聚反应的影响。发现溶剂配比、基体聚合物PBT-PTMG影响PPTA的转化率和PPTA的分子质量。通过FTIR研究发现PPTA中的酰胺键-NH-和PBT-PTMG的醚键特征吸收均向低渡数位移;通过用PBT-PTMG 的良溶剂二氯甲烷对复合物进行产抽提,结果发现,刚性链PPTA与PBT-PTMG分子链有较强的氢键相互作用,从而改进了分子间的相容性,获得了PPTA／PBT-PTMG的微相复合物。PPTA／PBT-PTMG的微相复合物有较好的力学性能。     

聚砜微球的制备及应用

通过W/O/W型双重乳液法制备聚砜(PSF)微球。研究聚乙烯吡咯烷酮(PVP)、油酸(OA)、吐温80,这些油相表面活性剂对微球形成的影响。并根据微球形貌的变化来检测水中的有机污染物。结果表明:利用油酸(OA)作为表面活性剂,可以得到蜂窝状聚砜微球。并且其对水中的N-甲基吡咯烷酮(NMP)有极端的敏感反应(NMP/水,1/107)。     

淀粉、蛋白质及聚丙烯酸之间相互作用的共振光散射光谱研究

基于共振光散射光谱(RLS)探索了牛血清白蛋白(BSA)与淀粉及聚丙烯酸(PAA)三者之间的相互作用机理,并分析了BSA与淀粉之间质量比率(MR=MBSA/MStarch)对三者之间相互作用的影响。结果表明,淀粉和BSA通过各自与PAA之间氢键作用而形成一种交联三元复合物,且结合过程优先发生在PAA与BSA之间。淀粉、BSA和PAA是构成此三元复合物的初级元素,淀粉/PAA和BSA/PAA是此三元复合物的二级结构单元。此外,它们之间的相互作用还与BSA溶液浓度的高低有着密切关系。     

壳聚糖微球及壳聚糖-明胶复合物微球的制备及缓释性能研究

采用乳化-化学交联法制备壳聚糖微球及壳聚糖-明胶复合物微球,并通过实验确定了最佳的成球条件:即m(壳聚糖)∶m(明胶)=2∶1 span-80用量为10g/100 mL,乳化剪切速度为600 r/min,交联率为60％,固化时间为40min.该方法制备的壳聚糖微球球形圆滑,粘连度小,亲水性好.此外在对壳聚糖药物缓释的研究基础上,对壳聚糖复合明胶后,对药物缓释的影响情况进行了研究探索.以生物可降解性和生物相容性好的壳聚糖和明胶为载体承载阿司匹林,研制出阿司匹林壳聚糖-明胶微球,为阿司匹林提供了一种理想的缓释载体.     

高岭石/聚苯乙烯插层复合物碳热还原反应制备碳化硅晶须/氧化铝复相陶瓷粉体

以二甲基亚砜(dimethylsuIfox.de,DMSO)为插层剂制得高岭石/DMSO插层复合物,将苯乙烯单体与高岭石,DMSO插层复合物进行置换反应, 成功地将苯乙烯单体引入高岭石层间,层间苯乙烯在加热条件下聚合,制得高岭石/聚苯已烯捅层复合物.以高岭石/聚苯乙烯插层复合物为原料,在氩气保护气氛下,于1500℃碳热还原反应制备碳化硅晶须/氧化铝(SiCw/Al2O3)复相陶瓷粉体.结果表明:在高岭石/聚苯乙烯插层复合物中,高岭石 的层间距由0.717nm扩张到1.130nm,插层率接近100%.插层作用影响了层间羟基基团的振动,使其键合方式发生改变.X射线衍射和扫描电镜分 析表明:合成出SiCw/Al2O3复相陶瓷粉体中SiC和Al2O3为主品相,SiC呈晶须状,其直径≤200nm,长度≥3μm.     

Oil palm microcomposites: Processing and mechanical behavior

The present work focuses on the effect of concentration and modifications of oil palm microfibrils in natural rubber. Increase in the concentration of microfibrils resulted in the reduction of tensile and tear strengths while an increase in modulus, hardness, and abrasion resistance of composites. The extent of microfibril orientation in the composite was determined from green strength measurements. Microcomposites were also prepared by using fibrils treated with benzoyl chloride, silane coupling agent, and hydrated silica‐resorcinol‐hexamethylenetetramine bonding agent. The treated and untreated microfibrils were characterized by FTIR. Scanning electron micrograph studies were carried out to analyze the microfibril pull out and fiber/matrix adhesion of composites. The extent of fiber alignment and interfacial adhesion were analyzed from swelling measurements. Finally, experimental results of mechanical properties were compared with the theoretical predictions. POLYM. ENG. SCI., 50:1853–1863, 2010. © 2010 Society of Plastics Engineers     

Interfacial behavior of microcomposites during creep at elevated temperatures

The high temperature interfacial behavior of SiC/C/SiC microcomposites was investigated. The interfacial sliding resistance dropped slightly from a room temperature value of 10 MPa with increasing temperature up to 1300°C in argon. The interfacial shear stress was shown to remain constant during the creep of microcomposites at 1200–1300°C and 200–450 MPa in argon. For creep in air, the interfacial shear stress increases at long exposure times.     

Morphology of polypropylene/silica nano‐ and microcomposites

The aim of this study was to compare the effects of different silica grades on the structure and morphology of isotactic polypropylene (iPP)/silica composites to better understand their structure–property relationships. Isotactic polypropylene composites with 2, 4, 6, 8 vol % of added silica fillers differing in particle size (micro‐ vs. nanosilica) and surface modification (untreated vs. treated surface) were prepared by nonisothermal compression molding and characterized by different methods. The addition of all silica fillers grades to the iPP matrix significantly influenced the spherulitic morphology, while phase characteristics of the iPP matrix seemed to be unaffected. Surface modification of silica fillers exhibited stronger effects on spherulite size than size of silica particles. Nonpolar silica particles, more miscible or compatible with iPP chains than polar silica particles, enabled better spherulitic growth. The spherulite sizes tended to reach equal values at 8 vol % of added silicas showing that spherulite size became independent of filler concentration and surface modification above optimum filler concentration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Structure and properties of microcomposites and macrocomposites from block polymers

The incorporation of a rubber phase in glassy polymers, as is well known in the case of high impact polystyrene, leads-to an increase in their impact strength. Block polymers offer three principal approaches for obtaining multiphase glassy polymers in which an elastorner phase is present in the matrix of the glassy polymer. They are: (1) control ofblock polymer composition, (2) blending of block polymer with homopolymers, and (3) polymerization of a solution.of a block polymer in the monomer corresponding to one of the blocks. The observed properties, such as impact strength, modulus, and heat distortion temperature, desired in rubber modified glassy polymers are discussed for block polymer systems prepared using the above approaches.     

Experimental and numerical investigation into fatigue damage mechanisms in multifibre microcomposites

Abstract

Polarised light microscopy has been used to investigate the influence of stress level, interfibre spacing, and fibre–matrix adhesion on the fatigue micromechanisms in carbon–epoxy model composites consisting of a planar array of five intermediate modulus carbon fibres. It was found that an increase in fatigue stress results in an increase in the number of fibre breaks, a more coordinated fibre fracture pattern as a result of fibre–fibre interaction, and extensive interfacial damage. In addition, it was shown that a smaller interfibre spacing results in a higher level of fibre–fibre interaction. Finally, in the case of surface treated carbon fibres (good fibre–matrix adhesion), a more coordinated fibre failure pattern was observed owing to stronger fibre–fibre interaction, whereas in the case of untreated carbon fibres (poor fibre–matrix adhesion), extensive debonding was observed which resulted in a more random fibre failure pattern. Finally, the experimental results were validated by means of a three-dimensional finite element analysis.     

Assembly of magnetic microcomposites from low pH precursors using a novel micro-fluidic-jet-spray-dryer

Spray drying is a convenient method to produce particles in high yields within a short period of time. The benefits of this technique include efficient uses of energy and solvent, and being a virtually waste-free process that allows for scale-up. A major drawback in conventional spray drying is the polydispersity of the produced particles. Herein, a specially designed spray dryer called micro-fluidic-jet-spray-drier (MFJSD) coupled with a micro-fluidic-aerosol-nozzle (MFAN) could generate droplets in a single trajectory pattern, to produce monodisperse particles. The drying temperature could vary from <90 °C to 300 °C to accommodate heat sensitive materials if necessary. For the first time we investigated the use of MFJSD to generate uniform magnetic microcomposites, specifically focusing on the effects of precursor composition, droplet size, and secondary heat treatment on the final properties of the particles. The presence of silica nanoparticles in the precursor was demonstrated to directly affect the morphology of the particles. Precursor containing silica nanoparticles generated particles with bowl-like shapes due to slower redistribution of solutes to support the particle skeleton during drying. In the absence of silica nanoparticles, the particles were almost perfectly spherical albeit with dimpled surfaces. After being subjected to calcination after drying, iron oxide crystals were found on the particle surfaces accounting for the overall magnetic property of the microcomposites, with lower magnetisation observed for particles containing higher amount of silica.     

Rheological and mechanical behavior of LDPE/calcium carbonate nanocomposites and microcomposites

The increase of the interest in polymer nanocomposites has been leading to continuous growing search toward nanofillers alternative to the widely known clay‐based ones. One of these possible alternatives is represented by calcium carbonate nanoparticles, which have not been widely investigated in such context. In this article, a study on the rheological and morphological behavior of different low density polyethylene‐calcium carbonate nanocomposites, compared with a reference calcium carbonate microcomposite, is presented. Several different nanosized calcium carbonates at different amounts were used. The results from the rheological and mechanical tests outlined that only minor changes occur when the amount is up to 2 wt %. The use of higher filler concentrations or the increase in the processing time can significantly affect this behavior. SEM analysis allowed deeper understanding of these phenomena. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interfacial effects on dielectric properties of polymethylmethacrylate‐titania microcomposites and nanocomposites

It is discussed that dielectric properties of polymethylmethacrylate (PMMA) composites are influenced by the particle size of titania as a result of changes in the structure and dynamics of polymer chains in the interphase regions around the particles. It is hypothesized that a loosely packed interphase layer, resulted from high stiffness and high cohesion energy of PMMA chains, provides enough free volume for segmental chain movements and dipole orientation along the applied electric field and causes an increase in dielectric properties of nanocomposites at low filler contents. It is shown that the attraction of PMMA toward micro‐titania and nano‐titania is similar by measuring the surface energy of fillers. Dynamics of polymer chains around fillers is investigated by dynamic‐mechanical‐thermal analysis and broadband‐dielectric spectroscopy, and presence of a loosely packed layer is confirmed by measuring thermal and mechanical glass transition temperature of composites. It is concluded that the anomalous enhancement in dielectric properties of 2 vol% nanocomposite, compared to the corresponding microcomposite, can be attributed to the higher volume fraction of loosely packed interphase layers in the nanocomposite. POLYM. COMPOS., 38:1158–1166, 2017. © 2015 Society of Plastics Engineers