环氧树脂/粘土纳米复合材料的制备与性能研究

研究了有机蒙脱土在环氧树脂中的插层和剥离行为,制备了两种环氧树脂/蒙脱土纳米复合材料并测试了其力学性能。实验结果表明,环氧树脂与有机土的相容性好,二者混合时环氧树脂很容易插入到粘土层间。使用经不同有机阳离子处理的两种有机蒙脱土,分别制得插层型和剥离型环氧/粘土纳米复合材料,力学性能结果表明,剥离型纳米复合材料的性能优于同组成的插层型纳米复合材料。     

胺类固化剂-插层剂体系对粘土在环氧树脂中剥离的影响

在对胺类固化剂-插层剂体系分析的基础上,选定叔胺类固化剂(BDMA)-Bronsted酸类插层剂(CH3(CH2)11NH3Cl)体系,制得了环氧树脂/粘土纳米复合材料,复合材料的XRD分析表明粘土在环氧树脂中已经剥离.结合有关研究成果,得出以下结论:在其他条件合适的情况下,只要插层剂为Bronsted酸类或者固化剂为叔胺类,就能得到剥离型的环氧树脂/粘土纳米复合材料.     

尼龙6/橡胶/天然粘土纳米复合材料的制备及其力学性能

采用一种新型的超细全硫化粉末橡胶/蒙脱土复合粉末(UFPRM),可以制备出剥离型的尼龙6/橡胶/天然粘土(尼龙6/UFPRM)纳米复合材料,所用的橡胶是一种具有特殊结构的超细全硫化粉末橡胶(UFPR).微观分析表明,橡胶粒子在尼龙6基体中分散良好,同时天然粘土在橡胶粒子之间的基体中剥离.在一定份数下,复合粉末可以同时提高尼龙6的韧性、刚性及耐热性;随着复合粉末含量的增加,材料的冲击强度进一步增加.而且,复合粉末对高分子量尼龙6的增强、增韧效果好于低分子量尼龙6.进一步研究发现,在适当的剪切速率下,尼龙6/橡胶/天然粘土纳米复合材料可以获得较好的综合力学性能.     

桐油酸酐固化环氧树脂/蒙脱土纳米复合材料的研究

通过阳离子交换的方法将蒙脱土进行有机化处理，使蒙脱土由亲水性变成亲油性且层间距扩大，采用浇模固化成型法制备环氧树脂／桐油酸酐／蒙脱土纳米复合材料，并用XRD，DMTA等手段研究有机蒙脱土在环氧树脂中的剥离行为，研究发现，加入桐油酸酐固化剂后，粘土被剥离而得到剥离型的纳米复合材料，而且工艺条件的变化并不明显改变剥离的效果，DMTA测试表明桐油酸酐固化的环氧树脂的玻璃化转变温度随着粘土的加入而降低。     

Preparation and properties of nitrile rubber/montmorillonite nanocomposites via latex blending

The nitrile rubber (NBR)/unmodified montmorillonite (Na-MMT) clay nanocomposites were prepared by latex blending method followed by melt mixing of compounding ingredients by using two-roll mill. The X-ray diffraction (XRD) studies showed an increase in the basal spacing and broadening of peak corresponding to crystal structure of Na-MMT indicating the formation of intercalated/exfoliated clay layers in the NBR matrix. Increase in clay content of nanocomposite increased the XRD peak height due to the formation of many of clay tactoids at higher loading. The transmission electron microscopy (TEM) strengthened the XRD finding by showing the presence of intercalated/exfoliated morphology of clay platelets having good dispersion. The modulus and tensile properties of the nanocomposites were improved with addition of Na-MMT which is proportional to clay concentration. The retention of tensile properties of aged nanocomposites, with all clay concentration, was superior to either pure NBR and carbon black filled NBR composite. The dynamic mechanical analysis showed proportional increase in storage modulus analogous to Na-MMT loading at all the temperature ranges due to the confinement of polymer chains between the clay layers. Nanocomposites with different proportions of clay showed a decrease in tan δ_max peak height with a shift towards higher temperature indicating the reduction in the segmental mobility of polymer chain. A linear model was proposed to correlate the influence of Na-MMT content on storage modulus of nanocomposites. Differential scanning calorimetry indicated a linear increase in glass transition of nanocomposites which is proportional to clay loading. Thermogravimetric analysis revealed a small improvement in the thermal stability of nitrile rubber/clay nanocomposites.     

Elastomeric epoxy nanocomposites: Nanostructure and properties

In polymer layered silicate nanocomposites, significant differences have been reported between the effects of the nano-reinforcement on rigid and elastomeric nanocomposites. In this paper, we have studied elastomeric nanocomposites based upon DGEBA epoxy resin filled with montmorillonite (MMT) and cured with a long-chain polyoxypropylene diamine, for comparison with analogous rigid nanocomposites. Ultrasonic mixing was used to disperse the MMT in the matrix to improve homogeneity and decrease the agglomerate size. Two different methods of nanocomposite preparation were used in which the MMT was first swollen with either the curing agent or the epoxy before the addition of, respectively, DGEBA or diamine. A better dispersion of the nanoclay in the matrix and a greater amount of intercalation occurred when the MMT was first swollen with the diamine. The effect of MMT concentrations up to 8 wt.% on the mechanical behaviour of the epoxy/MMT nanocomposites was investigated. It was found that the addition of MMT increased the tensile strength and modulus, although SAXS and TEM indicated that a significant fraction of the clay layers were not exfoliated. Nevertheless, the addition of the clay resulted in changes in the fracture surfaces, as indicated by SEM, consistent with the tensile results and indicative of toughening.     

一种促进粘土在环氧树脂中剥离的方法研究

使用对环氧树脂的固化反应有促进作用的有机阳离子对粘土进行有机化处理，得到的有机土与环氧树脂混合后，尽管其层间距较小，层间容纳的环氧树脂较少，但由于催化作用使层间环氧树脂固化较快，结果在环氧的固化过程中粘土更易剥离，从而得到粘土剥离程度较高的环氧树脂／粘土纳米复合材料。这一研究为制备粘土剥离程度更高、性能更好的环氧／粘土纳米复合材料提供了有效的方法。     

Mechanical and barrier properties of epoxy polymer filled with nanolayered silicate clay particles

The diglycidyl ether of bisphenol A (DGEBA) epoxy resin system filled with organo clay (OC) and unmodified clay (UC) were processed separately by two different curing agents. Triethylene tetramine (TETA) and Diaminodiphenyl methane (DDM) hardeners were used as curing agents. The nanocomposites were processed by shear mixing at different clay concentrations (1, 2, 3,5 and 10 wt%). The OC and UC were characterized by x-ray diffraction (XRD) technique. The morphology of the nanocomposites was obtained by XRD and Transmission Electron Microscopy (TEM). Bending and Impact tests conducted on these materials revealed that the organo clay filled epoxy resin showed good improvement in property over unmodified clay filled epoxy composites. The mass uptake of the nanocomposites was studied in the acid, base and water mediums. It is observed that the mass uptake in the acid medium is higher than in other mediums. The equilibrium mass uptake in all the mediums for nanocomposites was found to be lower compared to neat epoxy polymer system.     

Effect of clay and PEO-PPO-PEO block copolymer on the microstructure and properties of cyanate ester/epoxy composite

In this study, processing, morphology and properties of poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) triblock copolymer and clay modified cyanate ester/epoxy hybrid nanocomposites were investigated. The PEO-PPO-PEO triblock copolymer preferentially reaction-induced microphase separate into spherical micelles in the cyanate ester/epoxy matrix. PEO-PPO-PEO was used as both nanostructuring agent for cyanate ester/epoxy blended resin and thus the predominantly intercalated and few exfoliated platelets of were also observed with clay, which successfully reduced the brittleness of the cyanate ester/epoxy blended resin increasing the toughness of designed materials. The stiffness and heat resistance of the neat BCE/EP resin could be retained in the BCE/EP/F68/clay hybrid nanocomposites. The optimum property enhancement was observed in the hybrid nanocomposites containing 5 wt% PEO-PPO-PEO and 3 wt% clay. The thermo/mechanical properties of the hybrid nanocomposites depend on microstructure, dispersion state and the ratio between organic and inorganic modifiers content.     

Mode I interlaminar fracture behavior and mechanical properties of CFRPs with nanoclay-filled epoxy matrix

The mechanical properties and fracture behavior of nanocomposites and carbon fiber composites (CFRPs) containing organoclay in the epoxy matrix have been investigated. Morphological studies using TEM and XRD revealed that the clay particles within the epoxy resin were intercalated or orderly exfoliated. The organoclay brought about a significant improvement in flexural modulus, especially in the first few wt% of loading, and the improvement of flexural modulus was at the expense of a reduction in flexural strength. The quasi-static fracture toughness increased, whereas the impact fracture toughness dropped sharply with increasing the clay content.Flexural properties of CFRPs containing organoclay modified epoxy matrix generally followed the trend similar to the epoxy nanocomposite although the variation was much smaller for the CFRPs. Both the initiation and propagation values of mode I interlaminar fracture toughness of CFRP composites increased with increasing clay concentration. In particular, the propagation fracture toughness almost doubled with 7 wt% clay loading. A strong correlation was established between the fracture toughness of organoclay-modified epoxy matrix and the CFRP composite interlaminar fracture toughness.     

固化剂类型与固化条件对环氧/粘土纳米复合材料插层剥离行为的影响

本文作者选用了5种不同类型的胺类固化剂:二乙烯三胺(DETA),二氨基二苯基甲烷(DDM),2.4.6三(二甲氨基甲基)苯酚(DMP-30),增韧改性胺和低温固化改性胺。考察了固化剂类型,固化温度和时间对环氧树脂/粘土纳米复合材料插层剥离行为的影响。固化程度和粘土层间距分别采用FT-IR和XRD,TEM检测。结果表明:环氧/粘土的插层与剥离行为与所选用的五种固化剂类型关系不大,而主要取决于固化工艺参数。在合适的固化条件下,当环氧树脂在粘土层间的固化速度大于层外固化速度,达到基本固化时,就能实现粘土的剥离,得到环氧/粘土纳米复合材料。     

反应型有机修饰剂对环氧树脂/粘土纳米复合材料热/机械性能的影响

使带有环氧基团的三缩水甘油基对氨基苯酚(TGPAP)分别与溴代正丁烷(BB)、2-溴乙醇(BE)反应,合成了反应型粘土有机修饰剂溴化(正定烷基)双环氧基(4-环氧醚基)铵(TGPAPB)和溴化(2-羟乙基)双环氧基(4-环氧醚基)铵(TGPAPE)。用这两种修饰剂改性粘土,分别制备出具有相同反应官能团但与环氧树脂的相容性略有不同的两种有机化粘土(B-Clay和E-Clay)。再用“粘土淤浆复合法”制备出两种环氧树脂/粘土纳米复合材料,研究了两种反应型有机修饰剂对纳米复合材料的结构和性能的影响。结果表明：带有羟基的E-Clay以高度无规剥离形式均匀分布在环氧树脂基体中;而B-Clay则形成了无规剥离/插层混合结构。两种粘土均参与固化反应在环氧树脂基体和粘土片层间产生了较强的界面作用力,从而显著提高了纳米复合材料的拉伸强度。粘土质量分数为3%的两种纳米复合材料,其拉伸强度分别达到32.4 MPa(E-Clay)和28.0 MPa(B-Clay),比对应的纯环氧树脂聚合物分别提高了76.47%和52.51%。同时,这两种纳米复合材料的玻璃化转变温度(T_g)也略有提高。     

Preparation and characterization of melt-extruded thermoplastic starch/clay nanocomposites

A series of gelatinized starch–clay nanocomposites which exhibit intercalated and exfoliated structures have been developed. Various nanoclay dispersions were prepared (either by standard mixing or through the use of ultrasonics) prior to their combination with a high amylose content starch using high-speed mixing and extrusion technology. Intercalated and exfoliated type structures were observed in the sheet extruded nanocomposites using X-ray diffraction and transmission electron microscopy (TEM). Due to the hydrophilic nature of the gelatinized starch nanocomposite a novel preparatory technique was developed to produce nano scale sections for TEM. A range of plasticiser levels were used in conjunction with different unmodified nanoclays (sodium montmorillonite (Na-MMT) and fluorohectorite (Na-FHT)) having different cationic exchange capacities. It was shown that an optimum level of both plasticiser and nanoclay existed to produce a gelatinized starch film with the highest levels of exfoliation, resulting in superior properties. The use of ultrasonics was only advantageous in terms of clay dispersions at medium clay concentrations in the Na-MMT nanocomposites and higher clay concentrations in the Na-FHT, most probably due to the difference in cationic exchange capacity; however when the level of clay, water and starch was optimised an exfoliated structure was produced via standard mixing which exhibited comparable improvements in mechanical properties to ultrasonically treated samples.     

Thermal, mechanical and vibration characteristics of epoxy-clay nanocomposites

Diglycidyl ether of bisphenol-A (DGEBA) epoxy resin system filled individually with organoclay (OC) and unmodified clay (UC) were synthesized by mechanical shear mixing with the addition of diamino-diphenylmethane (DDM) hardener. The unmodified clay used was Na⁺-Montmorillonite (MMT) and the organoclay was alkyl ammonium treated MMT clay. The reinforcement effect of OC and UC in the epoxy polymer on thermal, mechanical and vibration properties were studied. X-ray diffraction (XRD) and Transmission electron microscopy (TEM) were used to study the structure and morphology of nanocomposites. Curing study shows that the addition of OC in epoxy resin aids the polymerization by catalytic effect, and UC addition does not show any effect in the curing behavior of epoxy polymer. Thermogravimetry analysis (TGA) shows enhanced thermal stability for epoxy with OC fillers than that of epoxy with UC fillers. The epoxy with OC fillers shows considerable improvement on tensile and impact properties over pure epoxy polymer and epoxy with UC fillers. The improvement in tensile and impact properties of nanocomposites is supported with the fracture surface studies. Epoxy with OC fillers shows enhanced vibration characteristics than that of the pure epoxy polymer and epoxy with UC fillers.     

Development and characterization of active nanocomposites with embedded shape memory alloy wires

Active nanocomposites of epoxy resin containing bentonite clay and shape memory alloy (SMA) were made to evaluate the thermomechanical behavior in the range of phase transformation of shape memory alloy during heating. The epoxy resin system studied was prepared using bifunctional diglycidyl ether of bisphenol A (DGEBA), crosslinking agent diaminodiphenylsulfone (DDS), purified bentonite organoclay (APOC) and thin Ni‐Ti shape memory alloy wires. The evaluated ratio DGEBA/DDS was 100:40, for the epoxy resin/clay system was 100:1 and the shape memory alloy volumetric fraction of Ni‐Ti wires were 1.55%; 2.56%; 3.57% and 4.54%. The formation of nanocomposite was confirmed by X‐ray diffraction analysis. Phase transformation of the shape memory alloy wires were determined by differential scanning calorimetry (DSC). Specimens of the active nanocomposites were characterized mainly by dynamic mechanical analysis (DMA). According to the DMA results was evidenced a significant increase in glass transition temperature and storage modulus when 1 parts per hundred resin of clay is added to epoxy resin. A recover of storage modulus was observed in the active nanocomposite during heating in the range of the phase transformation of Ni‐Ti shape memory alloy wires when the volumetric fraction is above 3.5%.     

Evaluation of the influence of nanoparticles' shapes on the formation of poly(lactic acid) nanocomposites obtained employing the solution method

PLA nanocomposites were prepared by adding organically modified montmorillonite clay (Viscogel B8) and a homoionic clay (NT25), as well as unmodified silica (A200) and modified organic silica (R972). All nanocomposites were obtained by the solution intercalation method using chloroform as a solvent. The materials obtained were essentially characterized by X-ray diffraction and low-field nuclear magnetic resonance relaxometry, through the measurement of proton spin-lattice relaxation time (LF-NMR). Both clays and silicas used to obtain the polymeric nanocomposites showed good dispersion in the polymeric matrix. The relaxation times were distinct for each type of nanoparticle used. The nanocomposite formed with homoionic clay, NT25, presented an increase in the relaxation data, indicating formation of intercalated nanocomposites, contrary to the action of the organoclay Viscogel B8, which preferentially formed an exfoliated nanocomposite. When unmodified and organo-modified silica were added to PLA, an increase in the relaxation time of the polymer matrix was observed. According to the relaxation data, the organosilica R972 dispersed better in the polymeric matrix and consequently interacted better than the A200.     

Morphology/behaviour relationship of nanocomposites based on natural rubber/epoxidized natural rubber blends

In order to analyze the effect of an epoxidized natural rubber (ENR) and filler treatment on the morphology and behavior of natural rubber (NR) nanocomposites, blends of these polymers have been prepared. The nature and extent of the clay dispersions in the filled samples were evaluated by X-ray diffraction. In the presence of ENR, an exfoliated structure was obtained which suggests that enough rubbery polymer was incorporated into the interlayer spacing. The effect of clay in rubber compounds was analyzed through rheological, mechanical and swelling characterization. A sensible improvement in the nanocomposite properties was observed by the addition of organoclay. It has been deduced that the properties of the compounds strongly depend on the extent of the silicate nanolayers dispersion into the rubber matrices as well as on the organoclay type and elastomer compatibility.     

Effect of processing parameters and clay volume fraction on the mechanical properties of epoxy-clay nanocomposites

The influence of processing parameters and particle volume fraction was experimentally studied for epoxy clay nanocomposites. Nanocomposites were prepared using onium ion surface modified montmorillonite (MMT) layered clay and epoxy resin (DEGBF). Two different techniques were used for dispersing the clay particles in the epoxy matrix, viz. high-speed shear dispersion and ultrasonic disruption. The volume fraction of clay particles was systematically varied from 0.5 to 6%, and mechanical properties, viz. flexural modulus and fracture toughness, were studied as a function of clay volume fraction and the processing technique. The flexural modulus was observed to increase monotonously with increase in volume fraction of clay particles, while, the fracture toughness showed an initial increase on addition of clay particles, but a subsequent decrease at higher clay volume fractions. In general, nanocomposites processed by shear mixing exhibited better mechanical properties as compared to those processed by ultrasonication. Investigation by X-ray diffraction (XRD) revealed exfoliated clay structure in most of the nanocomposites that were fabricated. Morphologies of the fracture surfaces of nanocomposites were studied using a scanning electron microscopy (SEM). Presence of river markings at low clay volume fractions provided evidence of extrinsic toughening taking place in an otherwise brittle epoxy.     

酚醛树脂/蒙脱土纳米复合材料的制备及其泡沫的研究

采用原位聚合的方法将酸化的蒙脱土(H-MMT)与酚醛树脂(PF)进行复合,制成剥离型酚醛树脂/蒙脱土(PF/MMT)纳米复合材料和其泡沫体.用XRD和TEM对复合材料的结构进行研究,并对复合材料泡沫体的性能进行了测试.结果表明:H-MMT与酚醛树脂复合后能形成剥离型PF/MMT纳米复合材料,制成的泡沫中的MMT片层发生...     

Investigation of the nanomechanical properties of nylon 6 and nylon 6/clay nanocomposites at sub-ambient temperatures

The nanomechanical properties of nylon 6, nylon 6/exfoliated clay and nylon 6/non-exfoliated clay nanocomposites have been investigated from room temperature to ?10 °C in a controlled environment with humidity less than 1% RH. The hardness, elastic modulus and creep resistance of nylon 6 were improved in the nanocomposites across the temperature range. However, the effective reinforcement of the clay depended on the temperature due to the change between the glassy and transition states in the nylon. The exfoliated clay nanocomposite showed the greater improvements than in the non-exfoliated clay nanocomposite at all testing temperatures due to the improved constraint of the polymer chains by the clay platelets in the exfoliated structure. The surface mechanical properties of nylon 6 and the nanocomposites were also found to be highly sensitive to the moisture level during the tests; increasing the humidity in the room temperature tests resulted in a dramatic decrease in hardness and stiffness due to plasticisation by water molecules. The kinetics of the re-humidification process on nylon 6 were studied by monitoring the change in nanoindentation response. Analysis of the indentation creep revealed a significant change in the strain rate sensitivity when the humidity of the near-surface region probed by nanoindentation was in the vicinity of the glass transition.