疏水型PA6/SiO2有机无机杂化材料的制备及性能

以正硅酸乙酯(TEOS)、甲基三乙氧基硅烷(MTES)和己内酰胺(CPL)为原料,采用原位阴离子开环聚合法,制备了疏水型PA6/SiO2有机无机杂化材料。PA6/SiO2有机无机杂化材料表面外的Si-CH3基团赋予了材料优异的疏水性能。随着硅溶胶含量(SiO2%,质量分数)的提高,接触角θ增大,当SiO2%大于8.5时,接触角θ增大不明显,并最终稳定在130°左右。红外图谱(FT-IR)和X射线光电子能谱(XPS)分析结果显示,硅溶胶的羟基和未完全水解的烷氧基能够与PA6的前驱体发生杂化反应。X射线衍射结果显示,采用本实验方法制备出的PA6和疏水型PA6/SiO2有机无机杂化材均为α晶型,而DSC结果表明,PA6/SiO2有机无机杂化材料的熔点略高于PA6。     

聚己内酯/ 环氧树脂/ SiO2杂化材料的制备及性能

采用端硅氧烷基聚己内酯( PCL-TESi) 作为无机前躯物, 通过环氧树脂/ KB-2 的固化反应和PCL-TESi的溶胶2凝胶过程, 制备了聚己内酯/ 环氧树脂/ SiO₂ ( PCL/ EP/ SiO₂ ) 有机-无机杂化材料。利用红外光谱、透射电镜( TEM) 、热失重分析( TGA) 及在甲苯溶液中的溶胀试验对不同SiO₂ 含量的杂化材料进行分析。研究发现, 随着PCL-TESi 含量增大杂化体系交联密度降低; 此杂化体系中存在环氧和Si —O —Si 两种交联网络, 微观上形成纳米两相结构; Si —O —Si 交联网络的形成显著提高了材料的耐热性能, 使失重5 %时的热分解温度从120.5 ℃(纯环氧树脂/ KB-2 体系) 提高到277.6 ℃(SiO₂质量分数为3. 84 %的杂化体系) 。      

笼型倍半硅氧烷(POSS)/环氧树脂有机无机杂化材料的热性能

为了提高环氧树脂(EP)的性能,采用具有氨基官能团的笼型倍半硅氧烷(POSS)改性.首先通过POSS与EP发生化学反应,形成有机无机杂化树脂;然后固化杂化树脂,得到POSS/EP有机无机杂化材料.文中研究了杂化树脂的凝胶特性和杂化材料的热性能,包括热变性温度(HDT)、玻璃化转变温度(Tg)和高温热分解性能.研究结果表...     

聚醋酸乙烯酯/二氧化硅杂化材料的制备与性能研究

以硅酸钠在HCl溶液中的水解,经四氢呋喃(THF)萃取,制备聚硅酸溶胶,再与聚醋酸乙烯酯(PVAC)的THF溶液混合,经溶胶-凝胶过程制备了PVAC/SiO2有机/无机杂化材料.用扫描电镜(SEM),红外光谱(IR),X射线衍射,热失重及透光率等的分析测试,对制备的PVAC/SiO2杂化材料进行了结构与性能的研究.结果表明:本法制备的杂化材料中SiO2在PVAC的基体中分布均匀,SiO2在非晶态的PVAC中亦呈无定形态,杂化材料的硬度、软化温度和热分解温度都比纯PVAC有较大的提高;SiO2含量少于40%的杂化材料其断裂伸长率、屈服强度和断裂强度也比纯PVAC提高;另外,还发现在制备过程中加入少许偶联剂KH-570后,杂化材料中的有机-无机相间的相容性增加,不易发生相分离,材料的透光性能也大为改善.     

原位聚合法制备环氧树脂/纳米SiO2灌封材料的性能研究

采用原位聚合法制备了环氧树脂/纳米SiO2灌封材料.用透射电镜(TEM)、扫描电镜(SEM)、差热扫描量热法(DSC)等方法研究了材料的结构与性能.结果表明,环氧树脂/纳米SiO2灌封材料的冲击强度和弯曲强度随纳米SiO2含量而变化,当其含量为3%(质量分数)时二者出现最大值,与纯环氧树脂固化物相比冲击强度和弯曲强度分别提高了98%和112%.同时纳米SiO2的加入也使灌封材料的电性能和热性能得到改善,线膨胀系数明显降低,环氧树脂的粘度稍有增加.     

QCS/SiO_2有机/无机杂化膜的制备及其溶胀动力学研究

以季铵化壳聚糖(QCS)为主体膜材料,二氧化硅(SiO2)为无机前躯体通过溶胶-凝胶法制备QCS/SiO2有机/无机杂化膜,通过傅利叶变换红外光谱(FT-IR)、扫描电镜(SEM)和热失重分析(TGA)对制备得到的膜的结构、形貌以及热稳定性进行表征。同时,对QCS/SiO2杂化膜的溶胀机理、SiO2含量对该杂化膜溶胀度、溶胀速率和溶胀动力学的影响等因素进行了考察。结果表明:无机物质SiO2的含量对膜的溶胀过程有显著影响,随着SiO2含量的增加,溶胀速率常数呈现先增大而后减小的趋势。而且,该系列杂化膜在pH=7的水溶液中吸水溶胀时,溶胀过程遵循Schott’s二级溶胀动力学模型。另外,无机物质的引入优化了杂化膜的吸水溶胀过程,当杂化膜中无机物质SiO2含量为15%时(质量分数),初始溶胀速率(KsW2∞)为769.23,吸水速度较快。     

环氧树脂/超支化聚酯/纳米SiO2复合材料的制备及性能

采用超支化聚酯与聚硅酸溶胶共混改性环氧树脂,制备了环氧树脂/超支化聚酯/纳米SiO2三元共混体系纳米复合材料。研究了超支化聚酯/聚硅酸溶胶增韧改性环氧树脂固化体系的力学性能及热性能,通过X射线衍射(WAXD)、差示扫描量热(DSC)、热重分析(TGA)及扫描电镜(SEM)等测试手段对材料的微观相态结构与性能进行了表征。结果表明,超支化聚酯/聚硅酸的加入使纳米复合材料的力学性能和热性能得到明显提高。当纳米SiO2的含量为1%(质量分数,下同)时冲击强度比纯环氧树脂提高了10.48kJ/m2,材料的起始热分解温度也提高了27℃。     

聚醋酸乙烯酯／二氧化硅杂化材料的制备与性能研究

以硅酸钠在HCL溶液中的水解，经四氢呋喃（THF）萃取，制备聚硅酸溶胶，再与聚醋酸乙烯酯（PVAC）的THF溶液混合，经溶胶-凝胶过程制备了PCAC/SiO2有机/无机杂化材料。用扫描是镜（SEM），红外光谱（IR），X射线衍射，热失重及透光率等的分析测试，对制备的PVAC/SiO2杂化材料进行了结构与性能的研究。结果表明：本法制备的杂化材料中SiO2在PVAC的基体中分布均匀，SiO2在非晶态的PVAC中亦呈无定形态，杂化材料的硬度、软化温度和热分解温度都比纯PVAC有较大的提高；SiO2含量少于40%的杂化材料其断裂伸长率、屈服强度和断裂强度也比纯PVAC提高；另外，还发现在制备过程中加入少许偶联剂KH-570后，杂化材料中的有机-无机相间的相容性增加，不易发生相分离，材料的透光性能也大为改善。     

低收缩块状PMMA/SiO_2杂化材料制备及性能表征

以甲基丙烯酸甲酯(MMA)、正硅酸乙酯(TEOS)和硅烷偶联剂(MPMS)为原料,采用溶胶-凝胶法制备出低收缩、具有良好光学性能的PMMA/SiO2杂化材料。通过透射电子显微镜、差热分析、红外吸收光谱和紫外光-可见分光光度计表征了杂化材料的微观形貌、热性能和透明性。结果表明材料的网络结构相对比较均匀,在可见光波长范围内材料均一性好;有机相和无机相之间是通过共价键相互连接的,没有出现有机相、无机相分离现象;杂化材料的透光率约90%。     

高模量、低热膨胀系数聚酰亚胺杂化薄膜的制备

通过在聚酰胺酸中加入正硅酸乙酯(TEOS)和硅烷偶联剂(KH550),制备了不同SiO2含量的PI/SiO2杂化薄膜.采用FTIR、TMA、SEM以及TGA分析了PI/SiO2杂化薄膜的性能和结构.结果表明,TEOS经水解缩合与聚酰亚胺(PI)形成了有机-无机杂化网络结构,SiO2均匀分散在聚酰亚胺基体中;SiO2和偶联剂的引入提高了杂化薄膜的热稳定性;随着SiO2含量的增加,PI/SiO2杂化薄膜的拉伸强度降低,但当SiO2含量达到20%时,弹性模量增大到3.4GPa.     

Engineering the coefficient of thermal expansion and thermal conductivity of polymers filled with high aspect ratio silica nanofibers

The thermomechanical properties of epoxy filled with two different types of silica nanofillers: spherical nanoparticles and nanofibers were investigated as a function of silica nanofiller aspect ratio and concentration. Results indicated that at room temperature and at 8.74% silica nanofiber concentration (by volume) the thermal conductivity of epoxy increased twofold and coefficient of thermal expansion (CET) decreased by ∼40%. Silica nanofiber filled epoxy showed 1.4 times greater CET and 1.5 times greater thermal conductivity compared to spherical nanoparticle filled epoxy. The significant changes observed in thermomechanical properties of silica nanofiber filled epoxy were attributed to its high aspect ratio by constraining the polymer matrix as well as reducing the phonon scattering due to the formation of a continuous fiber network within the matrix. In addition to being electrically insulating, the improved properties of silica nanofiber filled epoxy make it an extremely attractive material as underfill and encapsulant in advanced electronic packaging industry.     

Substantiating the role of phase bicontinuity and interfacial bonding in epoxy-silica nanocomposites

Nanocomposites consisting of an epoxy network matrix and a silica reinforcing phase were produced from a resin mixture functionalized with alkoxysilane coupling agents. Particulate nanocomposites were obtained by dispersing silica-organosol particles in the resin, while bicontinuous phase nanocomposirtes were obtained by the in-situ hydrolysis and condensation of tetraethoxysilane containing minor amounts of γ-glycidoxyl trimethoxysilane. Functionalization of the epoxy resin with an amine silane coupling agent was found to be more effective in aiding the dispersion of silica sol particles in the resin than the corresponding resin functionalized with a mercaptan silane coupling agent. Similar differences in the efficiency of coupling agent grafted on to the epoxy resin were observed for bicontinuous phase nanocomposites. The amine silane functionalization produces denser silica domains, which results in a higher rubber-plateau modulus and higher resistance to solvent penetration. The study also showed that the particulate nanocomposites are very ineffective in improving the solvent resistance of the base resin, even when the resin is grafted with a very efficient amine silane coupling agent, which promotes interfacial bonding. The different types of morphology were characterized by transmission electron microscopy and small angle X-ray scattering analysis.     

Preparation and characterization of water-borne epoxy shape memory composites containing silica

Shape memory silica/epoxy composites were successfully prepared by hydrolysis of tetraethoxysilane (TEOS) within the epoxy matrix via latex, freeze-drying, and hot-press molding method. The silane coupling agent 3-triethoxysilylpropylamine (KH550) was introduced to improve the interfacial properties between the in-situ generated silica particle and epoxy matrix. The morphology structure and the effect of the content of the in-situ formed silica on the mechanical and shape memory properties of the silica/epoxy composites were studied. The experimental results indicated that the silica particles were homogenously dispersed and well incorporated into the epoxy matrix. Significant improvements were achieved in the mechanical property of the organic–inorganic hybrid materials. The silica/epoxy composites exhibited high shape recovery and fixity ratio approximately 100% even after 10 thermo-mechanical cycles.     

The influence of multiscale fillers on the rheological and mechanical properties of carbon-nanotube–silica-reinforced epoxy composite

Multiscale fillers were fabricated through synthesis of carbon nanotubes (CNTs) on silica microparticles by the use of chemical vapor deposition. Three types of catalyst precursors with different concentrations and reaction times were investigated to find the optimal conditions for CNT synthesis. The produced multiscale fillers of CNT–silica were incorporated within epoxy resin to fabricate a multiscale composite. Rheological analysis and tensile and impact tests were performed to study the effect of fillers on the structural properties of composites. The rheological results demonstrated a similar viscous behavior between CNT–silica suspensions and epoxy, which implies that there was no critical increase of viscosity. Significant improvements in the elastic modulus and tensile and impact strength were achieved for epoxy matrix filled with the optimal fraction of multiscale fillers. The reinforcing efficiency of multiscale fillers was evaluated by comparing the results of micromechanical models with experimental data.     

Mechanical properties of nano-silica particulate-reinforced epoxy composites considered in terms of crosslinking effect in matrix resins

In this study, the mechanical properties of nano-silica particulate-reinforced epoxy composites with different crosslinking densities were clarified experimentally to consider the interaction effects between nano-particles and the network structure in matrix resin. The matrices were prepared by curing with an excessive mixture of diglycidyl ether of bisphenol A type epoxy resin as the curing agent for the stoichiometric condition. The volume fraction of the silica particles with a median diameter of 240 nm was constantly 0.2 for every composite. The crosslinking densities and glass transition temperatures of the neat epoxy resins were identified from thermo-viscoelastic properties measured by dynamic mechanical analysis. Elastic moduli and strengths of the composites and the neat epoxy resins were measured by three-point bending tests. The glass transition temperatures of the neat epoxy resins decreased linearly as the crosslinking densities decreased from the stoichiometric condition. The glass transition temperatures of the composites were reduced by adding the nano-silica particles. The bending moduli of the composites in the glassy state could be predicted by using a mixture law of the composites regardless of the crosslinking densities and glass transition temperatures. The bending strengths were found to be sensitive to the crosslinking densities: they were both higher (for composites with high crosslinking densities) and lower (for composites with low crosslinking densities) than those of the neat epoxy resin. These results demonstrate that the interaction between nano-particles and network structures reduces the bending strengths, especially for low crosslinking densities.     

Strength of unidirectional glass/epoxy composite with silica nanoparticle-enhanced matrix

A technique was developed to improve the strength of unidirectional composites by enhancing the matrix properties through nanoparticles infusion. A commercially available standard DGEBA epoxy with silica nanoparticles (Nanopox F 400) was used as the matrix to make fiber composites. The silica nanoparticles in Nanopox were grown in situ via a sol–gel process resulting in a concentration of 40 wt% which was later diluted to 15 wt% particle loading. TEM images showed very uniform dispersion of silica nanoparticles with a size distribution of about 20 nm. Compression test revealed a substantial improvement (40%) in elastic modulus of the modified epoxy. A modified vacuum assisted resin transfer molding process was used to fabricate unidirectional E-glass fiber reinforced silica/epoxy nanocomposites. Inclusion of silica nanoparticles dramatically increased the longitudinal compressive strength and moderately increased the longitudinal and transverse tensile strengths. A microbuckling model was used to verify the compression testing results.     

Influence of addition of silica particles on reaction-induced phase separation and properties of epoxy/PEI blends

Polyether imides (PEI)/silica nanocomposites, prepared by sol–gel process, were used to modify the epoxy resin (ER), and the effect of silica particles on reaction-induced phase separation and mechanical properties of these systems were investigated. SEM images of the fracture surface of ER/PEI/silica composites showed an interesting morphology transformation with the increase of silica particle content. SEM–EDX results indicated that silica particles once formed in the PEI gradually migrated and concentrated in epoxy-rich region during the phase separation because of the better affinity between silica particles and epoxy resin. FTIR measurement and rheological test confirmed that the silica particles make the polymerization reaction of epoxy faster and the dynamic DSC results demonstrated that the activation energy of these systems decreased with the increase of the silica particles. Mechanical measurements approved that the introducing of PEI/silica nanocomposites into the epoxy could lead to great improvement of the impact strength and storage module.     

环氧网络结构设计与复合材料增韧的研究

本文以自由体积理论,对BF₃MEA固化环氧网络结构与T_g的关系进行了研究,并分析了组分对网络T_g的贡献,为确定固化剂的影响,对BF₃MEA及DDS固化环氧网络的断裂韧性进行了测试。结果表明,DDS固化体系的韧性要比BF₃MEA固化的相应的环氧网络的高。根据理论分析及实验结果,对复合材料基体的网络结构进行了重新设计,在提高复合材料层间韧性的同时保证其耐热性不会下降。实验结果验证了这一设想。     

Characterization of transverse tensile, interlaminar shear and interlaminate fracture in CF/EP laminates with 10 wt% and 20 wt% silica nanoparticles in matrix resins

The transverse tensile properties, interlaminar shear strength (ILSS) and mode I and mode II interlaminar fracture toughness of carbon fibre/epoxy (CF/EP) laminates with 10 wt% and 20 wt% silica nanoparticles in matrix were investigated, and the influences of silica nanoparticle on those properties of CF/EP laminates were characterized. The transverse tensile properties and mode I interlaminar fracture toughness (G_IC) increased with an increase in nanosilica concentration in the matrix resins. However, ILSS and the mode II interlaminar fracture toughness (G_IIC) decreased with increasing nanosilica concentration, especially for the higher nanosilica concentration (20 wt%). The reduced G_IIC value is attributed to two main competing mechanisms; one is the formation of zipper-like pattern associated with matrix microcracks aligned 45° ahead of the crack tip, while the other is the shear failure of matrix. The ratio of G_IIC/G_IC decreased with the concentration of silica nanoparticles, comparable with similar CF/EP laminates with dispersed CNTs in matrix. Fractographic studies showed that interfacial failure between carbon fibre and epoxy resin occurred in the neat epoxy laminate, whereas a combination of interfacial failure and matrix failure occurred in the nanosilica-modified epoxy laminates, especially those with a higher nanosilica concentration (20 wt%).     

Mechanical properties of epoxy composites reinforced with a low volume fraction of nanosilica fillers

In this paper we focus on the preparation and mechanical properties of the nanosilica-reinforced, epoxy resin Epikote 828LVEL. Epoxy composites containing two sizes of spherical silica nanoparticles, 130 nm and 30 nm, were prepared at a fixed volume fraction (V_P = 0.5%). To prevent agglomeration, the silica fillers were initially pre-treated with diglycidyl ether of bisphenol A (BADGE). Due to the low content of silica fillers, their inclusion in the matrix was confirmed by the increased roughness of a fracture surface compared to the smooth surface of the neat epoxy. Raman spectroscopy was employed to obtain additional information about the crack-propagation path. The mechanical properties, characterized by a three-point bending test, revealed a 10–20% increase in the composite's modulus of elasticity with 30-nm and 130-nm silica-filler inclusions. Elongation at break, on the other hand, decreased for 5–10% in both composites compared to neat epoxy, suggesting brittle fracture behavior in silica/epoxy composites. The fracture toughness results showed a 25–30% improved toughening for both composites compared to the pure epoxy. The composite's resistance to failure in terms of the impact energy was, however, strongly dependent on the size of the silica: we observed a 30% increase for the 130-nm, and a 60% increase for the 30-nm, silica/epoxy composites, compared to the pure epoxy.