硅橡胶/丁基橡胶共混体系的相容性研究

采用机械共混法制备了硅橡胶/丁基橡胶共混材料。通过理论分析、红外、动态力学性能、扫描电镜等初步考察了共混体系中硅橡胶和丁基橡胶的相容性。结果表明:硅橡胶/丁基橡胶共混体系属于热力学不相容体系,当丁基橡胶用量为50份时,硅橡胶呈连续相,丁基橡胶为分散相,随丁基橡胶用量的增加,硅橡胶和丁基橡胶呈部分双相连续的状态。     

Giant barocaloric effects in natural graphite/polydimethylsiloxane rubber composites

Journal of Materials Science - Solid-state cooling based on caloric effects is considered a viable alternative to replace the conventional vapor-compression refrigeration systems. Regarding...     

Conductive rubber composites from different blends of ethylene-propylene-diene rubber and nitrile rubber

Conductive rubber composites were derived from different blends of ethylene-propylene-diene monomer (EPDM) rubber and acrylonitrile butadiene rubber (NBR) containing acetylene black. The electrical and mechanical properties of these composites were measured. The percolation limit for achieving high conductivity of conductive filler depends on the viscosity of the blend. The higher the viscosity, the higher is the percolation limit. The conductivity rises with increasing temperature, and the activation energy of conduction increases with the decrease in the loading of conductive filler and percentage of NBR in the blend. Electrical hysteresis and an electrical resistivity difference during the heating-cooling cycle are observed for these systems, which is mainly due to some kind of irreversible change occurring in the conductive networks during heating. The mechanisms of conduction of these systems were discussed in the light of different theories. It was found that the degree of reinforcement by acetylene black in blends compares with those in the pure components NBR and EPDM. This is due to incompatibility of two elastomers in the blend. This revised version was published online in November 2006 with corrections to the Cover Date.     

Magnetic and processability studies on rubber ferrite composites based on natural rubber and mixed ferrite

Polycrystalline single phasic mixed ferrites belonging to the series Ni_1–x Zn _x Fe₂O₄ for various values of _x have been prepared by conventional ceramic techniques. Pre-characterized nickel zinc ferrites were then incorporated into a natural rubber matrix according to a specific recipe for various loadings. The processability and cure parameters were then determined. The magnetic properties of the ceramic filler as well as the ferrite loaded rubber ferrite composites (RFC) were evaluated and compared. A general equation for predicting the magnetic properties was also formulated. The validity of these equations were then checked and correlated with the experimental data. The coercivity of the RFCs almost resemble that of the ceramic component in the RFC. Percolation threshold is not reached for a maximum loading of 120 phr (parts per hundred rubber by weight) of the filler. These studies indicate that flexible magnets can be made with appropriate magnetic properties namely saturation magnetisation (M _s) and magnetic field strength (H _c) by a judicious choice of x and a corresponding loading. These studies also suggest that there is no possible interaction between the filler and the matrix at least at the macroscopic level. The formulated equation will aid in synthesizing RFCs with predetermined magnetic properties.     

Synthesis and characterization of polyaniline rubber composites

Composite films of polyaniline and synthetic rubber (cis-1,4-polyisoprene) were studied to understand the charge transport under pressure and temperature. Films of different compositions were prepared to measure current–voltage curves across the film thickness. The results reveal that these materials exhibit electrical conductivity as predicted by the classical theory of percolation. This has been discussed in the light of microscopic interaction between rubber and polyaniline aggregates. Pressure dependent electrical conductivity of these composites can be best explored to develop low cost pressure sensing materials.     

石墨烯硅橡胶复合材料的性能研究

本文采用复配的石墨烯、碳纳米管和氧化铝为导热填料制备了具有导热功能的有机硅复合材料。研究了石墨烯、碳纳米管和氧化铝的复配比例对复合材料体积电阻率、导热系数、拉伸强度等性能的影响;同时,以Gr-C-4#样品为基础配方,采用硅烷偶联剂Si-G-1分别对石墨烯、碳纳米管及氧化铝进行改性,并用改性后的填料配制石墨烯硅橡胶复合材料Gr-C-Si-1#,对比样品Gr-C-4^#与Gr-C-Si-1^#的性能差异,分析了改性复配填料对复合材料性能的影响。采用石墨烯硅橡胶复合材料对电缆终端进行了封装,对封装好的电缆终端开展了100、150、200A电流下的温升实验,未出现局部过热,并测定水浸泡前后的电缆终端电阻,封装后的电缆终端电阻未出现明显上升,实验结果表明本材料可以在电缆终端或中间连接处进行灌封,可对封铅连接处的良好的保护作用,工程应用意义重大。     

Preparation of a novel type of flame retardant diatomite and its application in silicone rubber composites

A novel strategy was used for preparation of flame retardant based on biomass debris to improve the flame retardant property of silicone rubber (SR). [(6-oxido-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methyl]butanedioic acid (DDP) was used to modify diatomite by esterification method, and DDP@diatomite was obtained. The structure and morphology of this novel additive was identified using Fourier transform infrared spectroscopy (FTIR), Brunner-Emmet-Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS) together with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS) techniques. Thermogravimetric (TG) analysis was performed to evaluate the thermal degradation behaviors of diatomite and DDP@diatomite. This novel additive was applied into silicone rubber (SR) composites. Combustion parameters, including heat release rate (HRR), total heat release (THR), smoke production rate (SPR), carbon monoxide (CO), peak smoke production rate (PSPR), peak carbon monoxide (PCO) and vertical burning time, were characterized by cone calorimeter and vertical burning tests. Results indicated that this flame retardant can reduce fire risk and toxicity effectively. TG and X-ray diffraction (XRD) patterns of SR and its composites were also investigated. The inexpensive property of modified diatomite could also expand its fire safe applications.     

Electrical properties of mixed rubber composites

Different rubbers (SBR, NR and MR) were mixed together in different ratios and each mixture was loaded with 40 p.h.r, (parts of rubber per hundred parts by weight) of HAF (high abrasion furnace) carbon black in an attempt to obtain a composite of good mechanical as well as electrical properties. The rate of relative rate of change of swelling, Q, in Kerosene (1/τ=(1/Q)dQ/dt) was found to decrease by increasing the ratio of both SBR and NR in the mixture, reflecting the difficulty of the solvent to penetrate the newly formed matrix. High electrical conductivity was detected in samples containing a high proportion of IIR. A slight decrease in the activation energies, associated with gradual decrease in the temperature coefficient of conductivity for all three mixed rubber composites, was noted. The σ(T) curves were found to change appreciably with increasing pre-extension for different sensitivities of all samples.     

导电硅橡胶复合材料压缩敏感性研究

分别对短切碳纤维和炭黑填充的硅橡胶基导电复合材料试样进行了单次与循环压缩试验,研究两种复合材料的压敏特性及可重复性。测试结果表明,两种导电复合材料都具有较好的压缩敏感性;碳纤维填充时,试样的灵敏度较高,达到250左右,且电阻相对值与应变之间基本呈线性关系;炭黑填充时,试样具有较好的可重复性,但灵敏度较差。通过导电机理研究,对两种导电复合材料不同的导电敏感特性进行了分析。     

Nickel and iron nano-particles in natural rubber composites

In this work, the mechanical, electrical, and magnetic properties of natural rubber (NR) composites containing iron or nickel nanoparticles at different percentage varying from 0 to 120 phr (part of magnetic particle per hundred rubber) have been investigated at room temperature. It was found that the optimum concentration of magnetic fillers in NR is 30 phr, which improve the rheometric characteristics and physico-mechanical properties. Magnetic properties of the rubber composites have been investigated using vibrating sample magnetometer (VSM) at room temperature. The magnetic measurements show superparamagnetic behavior for all Ni and Fe nanoparticles percentage. The electrical measurements show a strong dependency of the conductivity on the percentage of magnetic nanoparticles.     

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.     

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.     

橡胶相尺度对亚微米或纳米橡胶颗粒填充环氧复合材料性能的影响

对比研究了由液体橡胶在环氧树脂中原位形成的亚微米橡胶/环氧复合材料和在环氧树脂中直接添加纳米橡胶颗粒形成的纳米橡胶/环氧复合材料的性能。研究表明：未固化混合物的黏度随着纳米橡胶相的加入逐渐增加,但随着亚微米橡胶相含量的增加而降低;橡胶/环氧复合材料的玻璃化转变温度随着纳米橡胶颗粒的加入逐渐增加,但随着亚微米橡胶相含量的增加而降低;两种橡胶相的添加均使复合材料的弹性模量降低,断裂延伸率增加;在较低含量时,纳米橡胶颗粒可以提高环氧的拉伸强度;两种橡胶填充的橡胶/环氧复合材料均显示出明显的增韧效果。微观形貌分析表明,两种橡胶均可以在应力作用下脱粘并促进裂纹尖端的塑性变形。     

Carbon fibre composites with rubber toughened matrices

In carbon fibre reinforced plastics (CFRP), the initial resistance to crack propagation parallel to fibres is determined largely by the matrix toughness. The fracture toughness (G _IC) of an epoxide resin can be increased considerably by the addition of butadieneacrylonitrile co-polymers (CTBN). These cause the precipitation of small spheres of a second phase and, for example, increaseG _IC from ～ 300 to ～ 3000 J m^?2 on the addition of 9 wt% CTBN. The large increases obtained in bulk resins are not obtained in CFRP, instead significant but modest increases are achieved. The suppression of toughness is related to the thickness of resin film through which the crack propagates.     

Short silk fibre reinforced nitrile rubber composites

The role of resorcinol-hexamethylenetetramine-silica bonding system in adhesion between silk fibre and nitrile rubber has been studied. Definite proportions of the three components of the bonding system vis-à-vis fibre loading are found to provide the optimum set of technical properties. Increase of fibre concentration in the composites causes an increase in hardness, tensile strength, tear strength, modulus, heat build-up, compression set at constant strain, abrasion loss, and restriction to solvent-swelling and a simultaneous decrease in some properties like resilience, compression set at constant stress and elongation at break. Ageing enhances the adhesion level and shows improved retention of strength properties of the composites. Increasing fibre loading in the mixes leads to a significant improvement in processing characteristics. Scanning electron microscopy studies of fracture surfaces obtained from tensile, tear, abrasion and heat build-up testing have been made in order to assess the failure mode.     

环氧化天然橡胶改性石墨烯-炭黑/天然橡胶复合材料的制备及性能

以环氧化天然橡胶(ENR)为界面改性剂,制备了石墨烯-炭黑/天然橡胶-ENR(GR-CB/NR-ENR)复合材料,研究了ENR用量对GR-CB/NR-ENR复合材料的加工性能、力学性能和动态力学性能的影响。结果表明,ENR的加入可以改善GR-CB/NR-ENR复合材料的加工性能及CB粒子在天然橡胶基体中的分散性,增加GR与NR的相容性,增强填料与NR基体间的界面相容性,同时改善GR-CB/NR-ENR硫化胶的动态力学性能、物理性能和耐老化性能。当ENR添加量为6 wt%时,GR-CB/NR-ENR复合材料撕裂强度和拉伸强度最高,硫化胶耐老化性最好。随着ENR含量的增加,GR-CB/NR-ENR复合材料的压缩疲劳温度先升高后降低;随着应变的不断增大,GR-CB/NR-ENR复合材料的储能模量G'不断减小,损耗因子tanδ先增大后减小;动态模量随着应变的增加急剧下降。