Thermal stability and ablation properties of silicone rubber composites

Effects of incorporation of clay and carbon fiber (CF) into a high temperature vulcanized (HTV) silicone rubber, i.e., poly(dimethylsiloxane) (PDMS) containing vinyl groups, on its thermal stability and ablation properties were explored through thermogravimetric analyses (TGA) and oxy‐acetylene torch tests. Natural clay, sodium montmorillonite (MMT), was modified with a silane compound bearing tetra sulfide (TS) groups to prepare MMTS₄: the TS groups may react with the vinyl groups of HTV and enhance the interfacial interaction between the clay and HTV. MMTS₄ layers were better dispersed than MMT layers in the respective composites with exfoliated/intercalated coexisting morphology. According to TGA results and to the insulation index, the HTV/MMTS₄ composite was more thermally stable than HTV/MMT. However, addition of CF to the composites lowered their thermal stability, because of the high thermal conductivity of CF. The time elapsed for the composite specimen, loaded with a constant weight, to break off after the oxy‐acetylene flame bursts onto the surface of the specimen was employed as an index for an integrated assessment of the ablation properties, simultaneously taking into consideration the mechanical strength of the char and the rate of decomposition. The elapsed time increased in the order of: HTV < HTV/CF ≈ HTV/MMTS₄ < HTV/CF/MMTS₄ ≈ HTV/MMT < HTV/CF/MMT. This order was different from the increasing order of the thermal stability determined by TGA results and the insulation index. The decreased degree of crosslinking of the composites with MMTS₄ compared with that of the composite with MMT may be unfavorable for the formation of a mechanically strong char and could lead to early rupture of the HTV/MMTS₄ specimen. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical properties and processibilty of glass‐fiber‐, wollastonite‐, and fluoro‐rubber‐reinforced silicone rubber composites

The reinforcement of silicone rubber (SR) imparted by different types of fillers was investigated. Glass fiber (GF), wollastonite and fluoro rubber (FR) as nontraditional filler for rubber were compounded SR and mechanical properties of the prepared composites were evaluated. The addition of silane pretreated GF and wollastonite into SR, tensile strength, abrasion resistance and tear strength of the composites improved considerably. The improvement in the properties was assigned to an increased interaction between the filler and the polymer matrix. For the SR/FR composites system, the elongation at break was increase with increasing concentrations of FR due to sponge like structure resulting from poor compatibility between the two components. To investigate the production potential of extrusion processing method, prepared composites were extruded in a rod type sample. During the curing stage, GF, wollastonite and FR lead to the formation of void in the matrix resin. When GF and wollastonite were treated with silane, the void formations were reduced significantly. The silane treatment process improves not only mechanical strength but also processibility of SR composites in dry conditions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Vinyl-functionalized polyborosiloxane for improving mechanical and flame-retardancy performances of silicone rubber foam composites

In this work, we first synthesized vinyl-terminated polyborosiloxane (pBS) filler, and then incorporated it into silicone rubber foam (SRF) matrix to prepare composite materials through a simple chemical dehydrogenative foaming method under ambient conditions. The pBS filler with reactive groups could form physical and chemical crosslinking networks in SRF, leading to an excellent dispersion level of pBS in the SRF matrix. Moreover, the inserted pBS could remarkably improve the mechanical and flame-retardancy properties of SRF-pBS composites. Intriguingly, the SRF-pBS6 foam containing 6 wt% of pBS possessed a uniform porous structure and balanced mechanical properties (σ_b = 65.4 kPa, ε_b = 56.7%, compression stress 97.1 kPa), thermal conductivity (0.102 W (m K)^?1), limiting oxygen index (29.8%) and UL-94 rating (V-0) among the prepared foams. In addition, the incorporated pBS (6 wt%) could synergistically catalyze the formation of a silicon–boron strengthened ceramic-like protective layer under fire and was capable of suppressing heat and smoke production in the SRF-pBS6 foam. The present work provides a promising way for developing high mechanical and flame-retardant polymeric foam materials with good thermal insulation. © 2021 Society of Industrial Chemistry.     

碳纤维增强硅橡胶复合材料制备

由于硅橡胶具有较好的耐热性但力学性能比较差,本文用高性能的碳纤维作增强剂,硅橡胶（MVQ）作基相及偶联剂作为相容剂制备了碳纤维/硅橡胶复合材料。通过力学性能和热老化测试,确定碳纤维的用量。用偶联剂作相容剂研究了偶联剂对硅橡胶和碳纤维相容性影响;通过傅里叶变换红外光谱（FTIR)和扫描电镜(SEM)分析了碳纤维和硅橡胶交联结构和相容性。结果显示,制备了碳纤维/硅橡胶复合材料的最佳配方为硅橡胶 100份,碳纤维 12份,KH-550 2.5份。碳纤维增强硅橡胶的最佳硫化条件为：温度 175℃,压力为10MPa,时间为30min。由扫描电镜和红外光谱分析,进一步论证了用KH-550处理的比没有处理及用Si69处理的碳纤维与硅橡胶的混合相容性好。     

Investigation of silicone rubber composites reinforced with carbon nanotube,nanographite, their hybrid,and applications for flexible devices

New technology is constantly required for updating new generation flexible devices, such as stretchable sensors, flexible electronics, and actuators. In the present study, a stretchable strain sensor, and actuator were developed based on room-temperature-vulcanized (RTV) silicone rubber reinforced with carbon nanotubes (CNTs), nanographite (GR), and CNT-GR hybrids. A CNT-based strain sensor developed for RTV silicone rubber showed improved stiffness and brittleness. For example, at 5 phr of filler loading, the compressive and tensile modulus for the CNT-reinforced RTV silicone matrix improved by 287% and 240%, respectively. Similarly, the improvements in the compressive and tensile modulus were moderate for the CNT-GR hybrid (210% and 235%) and low for GR (135% and 125%). The improved brittleness resulted in a higher fracture strain of 170% and 155% for the CNT-GR hybrid and GR, respectively. The improved mechanical properties were tested in real-life applications of actuation. The actuation displacement at a filler loading of 2 phr increased to 1.65 mm (CNT), 1.25 mm (CNT-GR), and 0.08 mm (GR). From 2 to 8 kV, the actuation displacement increased by 825% (CNT), 830% (CNT-GR), and 32% (GR). The strain sensor showed a stretchability of >100% (CNT) and >100% (CNT-GR). In addition, the gauge factor was higher for the CNT-GR hybrid composites. The durability measurements showed that the change in resistance was negligible for up to 5000 cycles in both the CNT and CNT-GR rubber composites. A series of experiments confirmed that compared to the composite based on RTV silicone rubber and CNT, the CNT-GR hybrid showed a robust flexibility and stretchability as a piezo-resistive strain sensor and actuator.     

质子辐照对MQ硅树脂增强加成型硅橡胶力学性能的影响

采用空间综合辐照模拟设备研究了100keV和150keV能量的质子辐照对MQ硅树脂增强加成型硅橡胶力学性能的影响。结果表明,辐照后材料表面产生老化裂纹,随辐照能量、粒子注量的增加,裂纹的数量增多,裂纹增大;质子辐照对硅橡胶的力学性能影响较大,邵尔A硬度、拉伸强度和扯断伸长率随辐照粒子注量的增大先增加而后下降;小粒子注量的辐照对硅橡胶的损伤较小,以交联为主,而大粒子注量的辐照则以降解为主;高辐照能量对硅橡胶的损伤更为严重。     

玄武岩短纤维增强硅橡胶复合材料的制备及性能

采用玄武岩短纤维(BF)增强硅橡胶,制备了BF/硅橡胶复合材料,考察了硅烷偶联剂的种类、BF用量以及硫化条件对复合材料力学性能的影响,并用扫描电子显微镜观察了复合材料的微观形貌。结果表明,用KH 550对BF进行表面处理,所得复合材料的力学性能优于以Si 69处理的材料;当BF用量为20份时,BF/硅橡胶复合材料的力学性能最好;制备复合材料的最佳硫化条件为10 MPa×175℃×25 min;用KH 550处理BF,BF与硅橡胶的相容性比用Si 69处理的好。     

Effects of metal oxides on the dielectric and mechanical properties of silicone rubber composites

Polysiloxane dielectric elastomers have garnered a considerable deal of attention over the last decade due to their potential as electroactive soft materials. However, the intrinsic low dielectric constant of polysiloxanes has proven a serious limitation in their practical use. In this work, we controlled the dielectric properties of silicone rubber composites by changing the type and content of oxide fillers. The silicone-based dielectric elastomers with a high dielectric constant (5.21@1 kHz), low modulus (1.62 MPa), and high elongation (1100%) were successfully obtained. The effects of different types of metal oxides on the dielectric properties and mechanical properties of the prepared composites are further explored. Due to their excellent comprehensive features, these types of materials are expected to be applied in capacitive sensors, actuators, generators, and beyond.     

导热填料对室温硫化硅橡胶性能的影响

分析比较了氮化硅、氧化锌、勃姆石、氮化铝、碳化硅和石英粉等6种填料对室温硫化硅橡胶性能的影响,优选出氮化硅作为导热填料。比较了不同粒径的氮化硅性能,制备了综合性能较好的导热室温硫化硅橡胶。     

填料对双组分缩合型室温硫化硅橡胶性能的影响

考察了多种补强填料和半补强(或增量)填料如硅藻土、碳酸钙和氧化铝等对室温硫化(RTV)硅橡胶的机械性能和介电性能的影响。结果表明,采用经六甲基二硅氮烷处理的气相法白炭黑或沉淀法白炭黑作填料时,RTV硅橡胶多方面的性能都有所提高;采用补强填料和半补强填料并用的RTV硅橡胶的性能优于使用单一补强填料的RTV硅橡胶;随着填料用量的增加,RTV硅橡胶的机械性能、相对介电常数和介质损耗因数都有一定程度的提高,但体积电阻率有所降低。     

纳米SiO2对有机硅树脂增强加成型硅橡胶性能的影响

以由单官能硅氧单元和四官能硅氧单元组成的有机硅树脂(简称MQ硅树脂)增强加成型硅橡胶为基体,采用机械共混方式加入少量纳米S iO2,研究了纳米S iO2对MQ硅树脂增强硅橡胶的性能影响。结果表明,纳米S iO2在硅橡胶中以聚集体的形式存在,大小约为几十到几百纳米;纳米S iO2填充MQ硅树脂增强的硅橡胶的邵尔A硬度、拉伸强度和扯断伸长率与未填充纳米S iO2的硅橡胶基本相当,撕裂强度增大;其高温热稳定性优于未填充纳米S iO2的硅橡胶,但其透明性稍有下降。     

Cure characteristics and mechanical properties of short nylon fiber‐reinforced nitrile rubber composites

Acrylonitrile butadiene rubber (NBR)‐based composites were prepared by incorporating short nylon fibers of different lengths and concentration into the matrix using a two‐roll mixing mill according to a base formulation. The curing characteristics of the samples were studied. The influence of fiber length, loading, and rubber crosslinking systems on the properties of the composites was analyzed. Surface morphology of the composites has been studied using Scanning Electron Microscopy (SEM). Addition of nylon fiber to NBR offers good reinforcement, and causes improvement in mechanical properties. A fiber length of 6 mm was found to be optimum for the best balance of properties. It has been found that at higher fiber loadings, composites show brittle‐type behavior. Composites vulcanized by the dicumyl peroxide (DCP) system were found to have better mechanical properties than that by the sulfur system. The swelling behavior of the composites in N,N‐dimethyl formamide has been analyzed for the swelling coefficient values. Composites vulcanized in the DCP system were found to have higher rubber volume fraction than that in the sulfur system, which indicates better rubber–fiber interaction in the former. The crosslink densities of various composites were also compared. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1023–1030, 2004     

Thermal and mechanical properties of liquid silicone rubber composites filled with functionalized graphene oxide

To improve the thermal and mechanical properties of liquid silicone rubber (LSR) for application, the graphene oxide (GO) was proposed to reinforce the LSR. The GO was functionalized with triethoxyvinylsilane (TEVS) by dehydration reaction to improve the dispersion and compatibility in the matrix. The structure of the functionalized graphene oxide (TEVS‐GO) was evaluated by Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, X‐ray diffraction (XRD), and energy dispersive X‐ray spectroscopy (EDX). It was found that the TEVS was successfully grafted on the surface of GO. The TEVS‐GO/LSR composites were prepared via in situ polymerization. The structure of the composites was verified by FTIR, XRD, and scanning electron microscopy (SEM). The thermal properties of the composites were characterized by TGA and thermal conductivity. The results showed that the 10% weight loss temperature (T₁₀) increased 16.0°C with only 0.3 wt % addition of TEVS‐GO and the thermal conductivity possessed a two‐fold increase, compared to the pure LSR. Furthermore, the mechanical properties were studied and results revealed that the TEVS‐GO/LSR composites with 0.3 wt % TEVS‐GO displayed a 2.3‐fold increase in tensile strength, a 2.79‐fold enhancement in tear strength, and a 1.97‐fold reinforcement in shear strength compared with the neat LSR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42582.     

Effect of hollow glass beads on density and mechanical properties of silicone rubber composites

In this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm³ with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface-modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface-modified HGB in mechanical properties was analyzed.     

短切碳纤维及碳纤维布增强硅橡胶复合材料的制备及力学性能

将短切碳纤维(CF)、白炭黑和甲基乙烯基硅橡胶(VMQ)共混后,与碳纤维布(CFC)复合制备VMQ复合材料.考察了CFC层数对复合材料的拉伸性能、邵尔A硬度、耐磨性能及动态力学性能的影响.结果表明,随着CFC层数的增加,复合材料的扯断伸长率基本不变,拉伸强度逐渐升高.与仅添加10份(质量,下同)CF的复合材料相比,加入...     

纳米二氧化钛对MQ硅树脂增强硅橡胶性能的影响

以MQ硅树脂增强加成型硅橡胶为基体,采用机械共混方式,加入少量纳米二氧化钛进行改性,制备了纳米二氧化钛改性硅橡胶。试验结果表明,MQ硅树脂增强的硅橡胶中,加入少量纳米二氧化钛改性后,能够改善硅橡胶的力学性能,其硬度和断裂伸长变化不大,而拉伸强度和抗撕强度提高,硅橡胶的耐热性也提高。溶胀实验表明,添加纳米粒子后,硅橡胶的溶胀比降低,凝胶质量分数和交联密度增加。     

Short sisal fiber‐reinforced tire rubber composites: Dynamic and mechanical properties

The world tendency toward using recycled materials demands new products from vegetable resources and waste polymers. In this work, composites made from powdered tire rubber (average particle size: 320 μm) and sisal fiber were prepared by hot‐press molding and investigated by means of dynamic mechanical thermal analysis and tensile properties. The effects of fiber length and content, chemical treatments, and temperature on dynamic mechanical and tensile properties of such composites were studied. The results showed that mercerization/acetylation treatment of the fibers improves composite performance. Under the conditions investigated the optimum fiber length obtained for the tire rubber matrix was 10 mm. Storage and loss moduli both increased with increasing fiber content. The results of this study are encouraging, demonstrating that the use of tire rubber and sisal fiber in composites offers promising potential for nonstructural applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 670–677, 2004     

不同孔隙结构的硅海绵材料及其力学性能研究

采用不同方法制备了密度和孔隙率相近、孔隙结构不同的2种硅海绵材料,并表征了其孔隙结构的差异,研究了2种孔隙结构明显不同的硅海绵材料在力学性能方面的差异。研究结果表明：硅海绵材料的孔隙结构对断裂强度、断裂伸长率、压缩应力应变及压缩应力松驰等力学性能有较大的影响。     

Facile preparation and flame retardancy mechanism of cyclophosphazene derivatives for highly flame-retardant silicone rubber composites

A novel and efficient flame retardant cyclophosphazene derivative Hexa (p-acetamidophenoxy) cyclotriphosphazene (HACP) was successfully prepared via a facile one-step reaction. The chemical structure of HACP was characterized and confirmed by FT-IR, ¹H and ¹³C NMR. Then the as-prepared HACP was incorporated into addition-cure liquid silicone rubber (ALSR) matrix to prepare highly flame-retardant rubber composites. It was found that the incorporation of HACP can significantly enhance the flame resistance of ALSR. Typically, the ALSR composites filled with 30 phr HACP achieved UL-94 V-0 rating and meanwhile the total heat release and total smoke release were decreased by 26.9% and 41.5%, respectively. Moreover, the flame-retardant mechanism of ALSR/HACP composites was investigated by TGA, Py-GCMS, FT-IR, SEM and EDX, confirming that HACP plays a significant role in capturing free-radicals and forming protective layers. This work designed a novel cyclophosphazene-based flame retardant to significantly enhance the flame retardancy of ALSR, which may offer some valuable inspiration for the fabrication of highly flame-retardant polymer composites.     

Ablation properties of zinc borate and aluminum hypophosphite filled silicone rubber composites

The ablative properties of epoxy modified silicone rubber composites filled with zinc borate (ZB) and aluminum hypophosphite (AHP) were studied. The decomposition of the added fillers and covering connection of residual on the substrate contribute to the improvement of heat insulation. The ablation test shows that the formation of a dense char layer with certain strength is key to improving the ablative properties. The optimal ablative performance is achieved when the concentration of ZB and AHP is 10 and 5 phr, respectively. Under such circumstances, the linear ablation rate is as low as 0.032 mm/s, which is about 61% lower than the pure silicone rubber. Furthermore, the structure and composition of the formed char layer were analyzed using X-ray diffraction analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy.