纳米氧化铝颗粒对高性能环氧树脂玻璃化转变温度的影响

采用机械分散工艺制备了Al2O3/环氧复合材料,研究了颗粒含量和颗粒表面改性对复合材料玻璃化转变温度(Tg)的影响规律。结果表明:微米颗粒的加入并未改变环氧树脂的Tg,而纳米颗粒的加入则产生了较大影响。当未表面改性的Al2O3纳米颗粒含量超过10%(质量分数,下同)时,复合材料的Tg开始下降;纳米颗粒含量为18%时,相比纯树脂体系,复合材料的Tg下降了约25℃。经过辛基硅烷表面改性的纳米Al2O3颗粒与树脂的相容性得到改善,对体系的增黏效果减小,复合材料的Tg降低幅度较小。     

环氧型丙烯酸酯橡胶增韧聚乳酸的结构与性能

采用甲基丙烯酸环氧丙酯与丙烯酸酯类单体共聚的环氧型丙烯酸酯橡胶(ACM)增韧聚乳酸(PLA)。冲击测试结果发现,随着ACM含量的增加,共混物冲击强度先增加后降低,增韧剂最佳的质量分数为25%,冲击强度可达到670J/m;拉伸性能测试表明,随着ACM含量增加,共混物的杨氏模量和屈服应力逐渐降低;ACM的玻璃化转变温度随着橡胶组分的增加逐渐上升,PLA相的玻璃化转变温度变化不明显;差示扫描量热(DSC)测得加入ACM后,PLA冷结晶温度降低;扫描电镜(SEM)发现橡胶粒子质量分数为10%时能均匀分散在PLA中,ACM含量增加,相区尺寸变大;形变区观察发现,ACM橡胶粒子发生空洞化,基体发生剪切屈服。     

埃洛石纳米管及液体橡胶改性环氧复合材料性能研究

通过超声辅助机械分散技术制备了环氧/埃洛石纳米管与环氧/埃洛石纳米管/液体橡胶复合材料,借助差示扫描量热仪、拉伸测试和扫描电镜等手段研究了其固化行为、拉伸性能和断面形貌。结果表明:埃洛石纳米管及柔性橡胶在环氧树脂中呈均匀的分散状态;埃洛石纳米管使环氧树脂的拉伸强度和模量增加,断裂伸长率降低;柔性橡胶/埃洛石纳米管按比例复配可平衡环氧树脂的强度、模量和韧性。     

纤维素纳米纤维对环氧树脂/聚己内酯共混体系结构及性能影响

以溶剂交换的方法将纤维素纳米纤维(CNF)均匀分散到环氧树脂,并结合熔融共混法成功制备了环氧/聚己内酯(PCL)/CNF复合体系。通过扫描电镜、拉力和冲击试验机考察了CNF的加入对环氧树脂/PCL共混体系形貌结构及性能影响。结果表明,CNF的加入对低浓度环氧树脂/PCL共混体系形貌结构及力学性能影响不大。而对高浓度环氧树脂/PCL共混体系形貌结构和力学性能影响较为明显:随着CNF加入量的增加,均能观察到比较明显的两相结构,但两相相区尺寸逐渐减小,PCL富集相的连续性增强;力学实验结果表明CNF的加入使材料的韧性和强度均能提高,冲击强度和拉伸强度分别较未添加CNF的体系提高了91%和24%。     

微纳米SiC/环氧树脂复合材料的界面和非线性电导特性

以微米和纳米SiC为填料,制备了不同填料配比的微纳米SiC/环氧树脂(EP)复合材料。测试了微纳米SiC/EP复合材料的玻璃化转变温度、室温介电谱和直流电导特性。分析了填料与基体之间的界面对玻璃化转变温度、介电谱及直流电导特性的影响。实验结果表明,在微米和纳米SiC填料的共同掺杂下,随着纳米SiC填料含量的增加,微纳米SiC/EP复合材料的玻璃化转变温度先降低后升高。在相同频率下,微纳米SiC/EP复合材料具有更低的相对介电常数和低频损耗峰幅值。与EP相比,微纳米SiC/EP复合材料具备显著的非线性电导特性。与微米SiC/EP复合材料相比,微纳米SiC/EP复合材料具有更高的非线性指数和阈值电场强度。微纳米SiC/EP复合材料的非线性电导特性与SiC颗粒和EP基体之间的界面区密切相关。      

填料含量对纳米BaTiO_3/环氧树脂复合体系介电性能的影响

通过采用机械共混法制备纳米BaTiO3/环氧树脂两相复合材料和纳米BaTiO3/环氧树脂/炭黑三相复合材料。观试了纳米BaTiO3/环氧树脂两相复合材料的微观形态、介电常数与介电损耗角正切,以及纳米BaTiO3/环氧树脂/炭黑三相复合材料的介电常数与介电损耗角正切,根据微观结构理论、极化理论以及渗流理论分析了纳米BaTiO3填料含量对纳米BaTiO3/环氧树脂复合材料微观形态和介电性能的影响,及导电相炭黑的加入对该复合体系介电性能的影响。     

热塑性颗粒-无机粒子协同增韧碳纤维增强环氧树脂复合材料

针对碳纤维增强环氧树脂(CF/EP)复合材料层间断裂韧性进行研究,通过在CF/EP复合材料层间添加四种无机纳米粒子和三种热塑性颗粒对其进行II型层间断裂韧性(G_IIC)研究,选择工艺性和增韧性效果好的两种无机纳米粒子和热塑性颗粒进行协同增韧研究。结果表明,CF/EP复合材料的G_IIC在适当的无机纳米粒子含量下都得到提高,这主要是由于无机纳米粒子在层间形成了有效吸收断裂能的微结构,纳米羟基氧化铝(AlOOH)的工艺性及增韧性等综合性能最好,AlOOH质量分数为1wt%时,CF/EP复合材料的G_IIC达到931 J/m2,提高了29.3%;热塑性颗粒中,改性聚芳醚酮颗粒(PAEK)的综合性能最好,添加10wt% PAEK,CF/EP复合材料的G_IIC可以提高32%,这是由于预制在层间的热塑性颗粒随着基体流动而得到扩散,形成了独特的跨层间连续结构,从而使裂纹扩展的阻力增加,有效提高了CF/EP复合材料的G_IIC;10wt%PAEK和1wt%AlOOH共同增韧CF/EP复合材料的G_IIC达到1 368 J/m2,相对于未增韧的CF/EP复合材料提高了90%,增韧效果比PAEK和AlOOH对CF/EP复合材料的增韧效果之和大,这表明,PAEK和AlOOH同时加入CF/EP复合材料层间,对CF/EP复合材料具有协同增韧效应。      

环氧树脂/纳米ATO复合材料的性能研究

将纳米ATO添加到环氧树脂中,采用超声波分散制备环氧树脂/纳米ATO复合材料,对复合材料的导电性能及物理机械性能进行了测试,并采用扫描电镜对复合材料的断裂形貌进行了分析.实验结果表明:复合材料的电阻率随着ATO含量的增加而减小,当ATO%=8%时,电阻率达到了105Ω·cm;随着纳米碳纤维的加入量的增加,复合材料的拉伸强度呈现一个先增加后减小的趋势,当ATO的质量分数为5%时,复合材料的力学性能最佳.     

氧化锌/环氧纳米复合材料的制备及其光学性能研究

采用均相沉淀法制备了氧化锌(ZnO)前驱体,通过煅烧前驱体制备了不同粒径的ZnO纳米颗粒,并在此基础上制备了ZnO/环氧纳米复合材料.借助TG、XRD和TEM等手段对纳米ZnO进行了表征,采用UV-VIS研究了ZnO含量、颗粒粒径等因素对复合材料光学性能的影响.研究结果表明:在紫外光区,提高ZnO的含量和选择ZnO最佳粒径,可以改善对紫外光的屏蔽效果;随着ZnO粒径的减小,ZnO对紫外光的屏蔽存在明显的蓝移现象,因此选择合适的粒径尤为重要.在可见光区,ZnO含量和颗粒粒径的影响相似,当ZnO含量低于0.07wt%、粒径小于27nm时复合材料的透过率几乎没有变化,增加含量或增大粒径透过率则随之下降.当ZnO的粒径为27nm时,添加0.07wt%的ZnO所制备的ZnO/环氧纳米复合材料具有优异的光学性能:在保持可见光区高透明性的同时又能够对紫外光区有良好的屏蔽效果,能够满足LED封装等光学器件的需要.     

橡胶纳米复合材料计算机模拟研究进展与挑战

总结了作者课题组采用分子动力学模拟研究橡胶纳米复合材料目前取得的主要进展,包括不同几何形状的纳米颗粒在橡胶基体中的分散机理、颗粒与橡胶分子链间的界面结合(聚合物玻璃化层是否存在)、颗粒对应力应变增强机理、碳纳米弹簧的引入对橡胶粘弹性的调控以及橡胶纳米复合材料非线性行为(Payne效应)产生的机理。模拟结果表明,存在一个最佳界面相互作用与接枝密度以实现纳米颗粒均匀分散;对于片状颗粒,在类似氢键界面相互作用时,存在聚合物玻璃化层。静态力学增强来自于两个方面:一是颗粒诱导分子链取向与排列,二是分子链吸附临近颗粒形成桥链在大变形下的有限链伸长。同时发现,碳纳米弹簧的加入会明显降低复合材料的滞后损失,并且得出纳米颗粒直接接触聚集与由分子链同时吸附多个颗粒成网对Payne效应非线性行为均有贡献。这些基础问题的澄清,将为制备动静态力学性能兼顾的橡胶纳米复合材料提供重要科学依据与理论指导,进而实现我国轮胎制品的高性能化与绿色化。最后针对橡胶纳米复合材料多层次多尺度结构与性能关系,简要评述了计算机模拟研究存在的挑战。     

Mechanical properties and fracture behaviors of epoxy composites with multi-scale rubber particles

In this work, we developed a strategy to balance the toughness and thermal resistance of epoxy composites by incorporating the multi-scale rubber particles. Two types of rubber i.e. the phase-separation-formed submicron liquid rubber (LR) and preformed nano-scale powered rubber (PR) particles were chosen as tougheners. It was found that the combination of these multi-scale rubber particles not only provides superior efficiency in enhancing the impact resistance of epoxy composites, but also results in balanced glass transition temperature. In particular, the highest gain in impact strength was obtained for the ternary composites containing 9.2 wt% submicron liquid rubber and 9.2 wt% nano-sized powered rubber which were ∼112% higher than the maximum enhancements of ∼49% and ∼66% for the corresponding binary composite systems with the single-phase rubber, respectively. The damage zone observation and fracture surface analysis suggested that the combined use of multi-scale particles was effective to promote matrix plastic deformation including void growth and shear banding induced by the improved rubber cavitation/debonding, which is likely responsible for the highly improved impact resistance of the ternary composites.     

Synthesis of nickel–rubber nanocomposites and evaluation of their dielectric properties

Nanocomposites based on natural rubber and nano-sized nickel were synthesized by incorporating nickel nanoparticles in a natural rubber matrix for various loadings of the filler. Structural, morphological, magnetic and mechanical properties of the composites were evaluated along with a detailed study of dielectric properties. It was found that nickel particles were uniformly distributed in the matrix without agglomeration resulting in a magnetic nanocomposite. The elastic properties showed an improvement with increase in filler content but breaking stress and breaking strain were found to decrease. Dielectric permittivity was found to decrease with increase in frequency, and found to increase with increase in nickel loading. The decrease in permittivity with temperature is attributed to the high volume expansivity of rubber at elevated temperatures. Dielectric loss of blank rubber as well as the composites was found to increase with temperature.     

Effect of hybridization of liquid rubber and nanosilica particles on the morphology, mechanical properties, and fracture toughness of epoxy composites

A liquid carboxyl-terminated butadiene–acrylonitrile copolymer (CTBN) and SiO₂ particles in nanosize were used to modify epoxy, and binary CTBN/epoxy composites and ternary CTBN/SiO₂/epoxy composites were prepared using piperidine as curing agent. The morphologies of the composites were observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), and it is indicated that the size of CTBN particles increases with CTBN content in the binary composites, however, the CTBN particle size decreases with the content of nanosilica in the ternary composites. The effects of CTBN and nanosilica particles on the mechanical and fracture toughness of the composites were also investigated, it is shown that the tensile mechanical properties of the binary CTBN-modified epoxy composites can be further improved by addition of nanosilica particles, moreover, obvious improvement in fracture toughness of epoxy can be achieved by hybridization of liquid CTBN rubber and nanosilica particles. The morphologies of the fractured surface of the composites in compact tension tests were explored attentively by field emission SEM (FE-SEM), it is found that different zones (pre-crack, stable crack propagation, and fast crack zones) on the fractured surface can be obviously discriminated, and the toughening mechanism is mainly related to the stable crack propagation zone. The cavitation of the rubber particles and subsequent void growth by matrix shear deformation are the main toughening mechanisms in both binary and ternary composites.     

Role of rigid nanoparticles and CTBN rubber in the toughening of epoxies with different cross-linking densities

Experimental investigations were conducted to characterize the fracture behaviours of Bisphenol A diglycidyl ether (DGEBA) epoxies modified with rigid nanoparticles (nanosilica or halloysite) and a reactive liquid carboxylterminated butadiene–acrylonitrile (CTBN) liquid rubber to identify toughening mechanisms and toughenability in the cured epoxies with different cross-linking densities. The epoxy was cured using three different hardeners, a heterocyclic amine (piperidine), a cycloaliphatic polyamine (Aradur 2954) and an aromatic amine [4,4′-Diaminodiphenyl sulfone (DDS)] to form nanocomposites with different cross-linking densities. It was found that both the hybrid particles, nanosilica with CTBN rubber and halloysite with CTBN rubber, were effective additives that clearly increased the fracture toughness of the three epoxy composites. In particular, the use of halloysite nanoparticles as additives for the epoxies showed greater potential than nanosilica to increase strength and modulus due to the reinforcing effect of the halloysite nanotubes (HNTs). The epoxy systems cured with the hardeners (Aradur 2954 and DDS), which generated relatively high cross-linking densities, evidenced inferior toughenability of the hybrid particles, compared with the epoxy systems cured using the hardener (piperidine), which produced lower cross-linking densities. The CTBN rubber formed dissimilar domains in different epoxy systems, features which were attributed to the different toughenability of the hybrid particles in the systems due to variations in the dominant toughening mechanisms involved.     

橡胶改性对硼纤维/环氧单向复合材料力学性能的影响

对环氧树脂进行液体丁腈橡胶改性, 并采用缠绕无纬布层压成型工艺制备了硼纤维/环氧单向复合材料。测试了环氧树脂液体丁腈橡胶改性前后硼纤维/环氧单向复合材料的力学性能, 研究了硼纤维/环氧单向复合材料的纵向拉伸破坏模式。结果表明, 基体中的10%液体丁腈橡胶使硼纤维/环氧单向复合材料的拉伸强度、 弯曲强度、 层间剪切强度和断裂延伸率分别提高了18.42%、 13.39%、 28.45%和43.40%, 但其拉伸和弯曲模量稍有下降。基体中含10%液体丁腈橡胶的硼纤维/环氧单向复合材料的纵向拉伸破坏模式为界面层的内聚破坏和脱黏破坏共存的混合破坏。      

Styrene-butadiene rubber/halloysite nanotubes composites modified by epoxidized natural rubber

The reinforcement effects of halloysite nanotubes on styrene-butadiene rubber and the modification effect of epoxidized natural rubber on styrene-butadiene rubber/halloysite nanotubes composites were studied. The structure, morphology and properties of styrene-butadiene rubber/halloysite nanotubes composites before and after the incorporation of epoxidized natural rubber were investigated. The results indicated that epoxidized natural rubber can promote the dispersion and orientation of halloysite nanotubes in styrene-butadiene rubber matrix at nanoscale and strengthen interfacial combination between halloysite nanotubes and styrene-butadiene rubber by the formation of covalent bonds and hydrogen bonds between epoxidized natural rubber and halloysite nanotubes. Consequently epoxidized natural rubber can improve the mechanical properties of the vulcanizates of styrene-butadiene rubber/halloysite nanotubes composites. Besides epoxidized natural rubber can decrease the rolling resistance of the vulcanizates and increase the wet grip property of the vulcanizates.     

Improved fracture toughness and fatigue life of carbon fiber reinforced epoxy composite due to incorporation of rubber nanoparticles

In this study, core–shell rubber (CSR) nanoparticles with approximate particle size of 35 nm were used as a modifier for the epoxy polymer. The effects of various CSR contents in the epoxy matrix on mode I interlaminar fracture toughness, tensile strength, and fatigue life of the carbon fabric reinforced epoxy (CF/EP) composites were investigated. The experimental results showed that the mode I interlaminar fracture toughness at crack initiation and propagation significantly improved by 71.21 and 58.47 %, respectively, when 8.0 wt% CSR was dispersed in the epoxy matrix. The fatigue life of the modified CF/EP composites at all of CSR contents dramatically increased 75–100 times longer than that of the unmodified CF/EP composites at high cycle fatigue while tensile strength slightly increased by about 10 %. Field emission scanning electron microcopy (FESEM) observations of the fracture surfaces were conducted to explain failure mechanisms of CSR addition to the CF/EP composites. The evidences of the rubber nanoparticle debonding, plastic void growth, and microshear banding were credited for delaying the onset of matrix crack, and reducing the crack growth rate, as a result, attributed to increase in the mechanical properties of the CF/EP composites.     

过氧化氢处理胶粉对橡胶-沥青黏弹性的影响

为了研究废胎胶粉经过氧化氢（H₂O₂）溶液处理后其孔结构和表观形貌的变化及对所制备橡胶-沥青高温性能的影响,采用三种不同比例的H₂O₂溶液对废胎胶粉进行表面改性处理,并制备橡胶-沥青。通过胶粉气体吸附试验、扫描电镜试验、沥青旋转黏度试验和动态剪切流变试验分析了不同比例的H₂O₂溶液对胶粉的孔隙结构、微观形貌和所制备橡胶-沥青的黏度、黏弹性等宏观力学性能的影响规律。结果表明:胶粉经H₂O₂溶液处理后,平均孔径明显变小,孔体积和孔面积的变化呈现一定的规律;随H₂O₂溶液比例的增加,胶粉颗粒间接触面增加,表面絮状物和孔隙增多,加强了胶粉与沥青的界面结合度。这使得胶粉中的橡胶烃在沥青中的溶解度增加,炭黑颗粒释放增多,胶粉颗粒的强度、弹性和耐磨性等力学性能下降,导致橡胶-沥青的弹性、黏度和高温抗车辙能力降低。      

Friction and wear of rubber/epoxy composites

The sliding wear rate and frictional coefficient of epoxy/rubber or epoxy/rubber/aluminium oxide composites were measured against themselves as a wear rate. The observed wear rate-sliding velocity data appear to be explicable by a recently proposed fatigue-shear model based on damage accumulation physics. The proposed equation seems to explain both dry and wet friction (water lubricant) environments. The microstructural features of a worn surface were examined using a scanning electron microscope (SEM) and related to the measured tribological data.     

纳米碳酸钙粉末橡胶复合粒子增强增韧聚氯乙烯

以纳米CaCO₃浆料和丁苯胶乳、 羧基丁苯胶乳、 丁腈胶乳为原料, 采用共凝聚法分别制备了三种纳米CaCO₃-粉末橡胶复合粒子, 并制备了三种纳米CaCO₃-粉末橡胶/聚氯乙烯(PVC)复合材料, 系统研究了复合粒子含量对PVC力学性能的影响, 并探讨了复合粒子的增强增韧机制。结果表明: 复合粒子在PVC树脂中分散均匀, 复合粒子中的纳米CaCO₃粒子以"裸露态"和橡胶"包裹态"两种形式存在于PVC基体中; 三种复合粒子均能显著提高PVC的缺口冲击强度, 纳米CaCO₃-粉末丁腈橡胶(CaCO₃-NBR)能同时起到增强增韧的效果, 而纳米CaCO₃-粉末丁苯橡胶(CaCO₃-SBR)在提高缺口冲击强度的同时也损失了PVC原有的刚性, 使其弯曲模量和拉伸强度大幅度降低, 纳米CaCO₃-粉末羧基丁苯橡胶(CaCO₃-X-SBR)的改性效果鉴于前两者之间; 复合粒子与PVC基体的相容性是影响复合粒子增强增韧改性效果的决定性因素, 相容性好的复合粒子能同时起到增强增韧的效果。