氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土纳米复合材料制备及其耐介质老化性能

采用原位聚合和混炼插层相结合技术制备了氢化丁腈橡胶/聚甲基丙烯酸镁/有机蒙脱土(HNBR/PMgMA/OMT)纳米复合材料,通过XRD,SEM和TEM等测试方法研究了HNBR/PMgMA/OMT纳米复合材料的结构、形态和性能.PMgMA离子簇与未反应完全的MgMA单体形成纳米-微米共存形态结构,PMgMA对HNBR有显著的增强效果,HNBR/PMgMA/OMT纳米复合材料具有良好的加工性能、物理机械性能和耐介质老化性能.TEM结果显示MgMA/OMT并用有助于OMT剥离分散,有机蒙脱土在硫化胶中形成以剥离和插层为主、反插层和未插层共存的微观结构;SEM显示当MgMA/OMT用量为20/10份时能明显改善复合材料的界面结合,此时纳米复合材料的拉伸强度、扯断伸长率和扯断永久变形分别为30.2 MPa,520%和30%;同时具有优异的耐热空气和耐油老化性能,耐热水性能也明显改善,在165℃的热空气、水和油中长期老化14天的老化系数分别达到0.61,0.63和0.84,其耐介质老化性能明显好于炭黑增强HNBR硫化胶及HNBR/PMgMA复合材料.良好的蒙脱土片层分散结构是提高HNBR/PMgMA/OMT纳米复合材料耐介质老化性能的主要原因.     

原位聚合甲基丙烯酸盐/低温氢化丁腈橡胶的结构与性能

采用不同阳离子的碱和甲基丙烯酸(MAA),通过混炼和硫化过程的原位聚合,制备了聚甲基丙烯酸盐(SPMAA)改性氢化丁腈橡胶(SPMAA-HNBR).用扫描电子显微镜、透射电子显微镜、傅里叶变换红外光谱仪、示差扫描量热仪及浸泡溶胀实验研究了SPMAA阳离子种类(Na+,Mg2+和Al3+)对SPMAA-HNBR性能的影响.结果表明,随着阳离子电荷数的增加,SPMAA逐渐在SPMAA-HNBR内部形成强的离子簇结构,导致其与HNBR间的相容性变差,甚至出现大尺寸的聚集体.这种明显的相分离结构造成聚甲基丙烯酸铝(Al SPMAA)改性氢化丁腈橡胶的拉伸强度和耐油溶胀性能都低于含电荷数较少的聚甲基丙烯酸钠(Na SPMAA)和聚甲基丙烯酸镁(Mg SPMAA)改性氢化丁腈橡胶的性能.各种SPMAA-HNBR的玻璃化转变温度均未发生变化,保持了-30℃的低温弹性.因此,选择生成不同阳离子的SPMAA,可在保持HNBR低温性能的基础上,有效控制SPMAA-HNBR的性能.     

利用静电界面制备高性能蒙脱石/氢化丁腈橡胶

将甲基丙烯酸(MA)和烷基胺改性蒙脱石(MMT)混合成浆料后,加入到氢化丁腈(HNBR)橡胶中,通过热硫化工艺,制备了MMT/HNBR橡胶复合材料.采用扫描电子显微镜、透射电子显微镜、小角X射线衍射仪、傅里叶变换红外光谱仪和转矩流变仪研究了MA改性的MMT与橡胶间的界面及分散性,并对复合材料的各种性能进行分析.结果表明,在热硫化过程中,不仅形成了橡胶的交联网络,而且也促使MA在橡胶中发生原位聚合.生成的聚甲基丙烯酸与MMT表面的烷基胺形成离子对,从而在橡胶和MMT间构筑了强的静电界面.同时MA在MMT层间发生聚合反应,提高了MMT在橡胶中的分散性.动态机械性能和200%应变的应力松弛实验表明,良好分散的MMT和静电界面有效约束了橡胶分子链在力学拉伸过程中的运动.与纯橡胶相比,MMT/HNBR橡胶复合材料具有更大的拉伸强度和韧性.此外,橡胶复合材料还具有良好的N2气阻隔性能.因此,配制MA/MMT浆料是一种简单方便的MMT改性方法,制备的MMT/HNBR橡胶复合材料可用于制造具有高强韧性和气体阻隔性要求的橡胶产品.     

高耐磨低生热NBR/TBIR复合材料的结构与性能

采用高反式-1,4-丁二烯-异戊二烯共聚橡胶(TBIR)对丁腈橡胶(NBR)进行改性, 制备了高耐磨、 低生热输送轮用白炭黑填充的NBR/TBIR橡胶纳米复合材料. 研究了NBR/TBIR橡胶纳米复合材料的交联密度、 物理力学性能及填料分散性, 探讨了材料的结构对性能的影响. 研究结果表明, 与纯NBR相比, NBR/TBIR橡胶纳米复合材料的硫化速率和交联密度随TBIR用量的增加而增大; 在保持NBR硫化胶基本力学性能、 耐老化性能和耐溶剂性能基本不变的前提下, TBIR的加入使NBR/TBIR硫化胶的耐磨性提高15%, 动态压缩生热降低5%, 动态压缩永久变形降低22%, 白炭黑分散水平提高; 与丁腈橡胶/顺丁橡胶[NBR/BR(80/20), 质量份数比]硫化胶相比, NBR/TBIR(80/20, 质量份数比)硫化胶具有更低的动态压缩生热和动态压缩永久变形及更好的填料分散性.     

TBIR应用于航空胎侧胶的热氧老化性能

研究了反式-1,4-丁二烯-异戊二烯共聚橡胶(TBIR)应用于航空轮胎胎侧胶[天然橡胶(NR)/顺丁橡胶(BR)/TBIR]的耐热氧老化性能.结果表明,与NR/BR硫化胶相比,10～20份质量的TBIR取代BR后,NR/BR/TBIR硫化胶的交联密度明显提高,压缩温升降低2. 2～3. 4℃,耐屈挠疲劳性能提高约100%,填料分散性改善,填料团聚体体尺寸减小,拉伸性能基本不变.随热氧老化时间延长,硫化胶的交联密度先增加后降低,并用TBIR的硫化胶交联密度在老化48 h后趋于平缓.与NR/BR相比,老化后的NR/BR/TBIR硫化胶生热最低,耐屈挠疲劳性最高.     

聚氨酯弹性体/蒙脱土纳米复合材料的合成与性能

采用聚氨酯本体预聚法 ,利用原位插层聚合合成了聚氨酯 蒙脱土纳米复合材料 .通过X 射线衍射(XRD)和Molau实验研究了蒙脱土在复合材料中的分散情况 .红外分析 (IR)表明随着蒙脱土含量的增加 ,复合材料羰基氢键减少 .动态力学分析 (DMA)以及差热分析 (DSC)结果说明随着蒙脱土含量的增加 ,材料的玻璃化温度降低 .聚氨酯纳米复合材料的拉伸强度和断裂伸长率同时提高 ,表现出较好的力学性能 .     

接枝改性碳酸钙及其在聚合物中的应用研究

介绍了近年来碳酸钙表面接枝改性的研究进展,讨论了自由基接枝聚合、辐照接枝聚合和力化学表面接枝聚合及偶联剂预处理与辐照并用接枝聚合改性方法。其中重点讨论了最新研究的偶联剂预处理与辐照并用接枝改性纳米碳酸钙的方法。用此方法制备的聚合物/纳米碳酸钙纳米复合材料在其他力学性能基本不变的情况下,大幅度提高了其缺口冲击强度和断裂伸长率。指出了碳酸钙表面接枝改性应向着提高接枝单体量和采用弹性体单体方面发展。     

纳米二氧化硅与辐射硫化三元乙丙橡胶相互作用的研究

用Kraus方程、IR光谱和交联密度等手段研究了纳米二氧化硅与辐射硫化三元乙丙橡胶间的相互作用。Kraus曲线显示纳米二氧化硅与辐射硫化三元乙丙橡胶之间存在着相互作用；红外光谱的结果表明纳米二氧化硅与橡胶分子发生了化学反应，生成了化学键。用平衡溶胀法测定了纳米二氧化硅填充辐射硫化三元乙丙橡胶的交联密度，发现当填料含量低于40phr时，填充辐射胶的总交联密度随填料用量增加而提高；继续增加填料含量，总交联密度不再继续提高；物理交联密度也呈现出相同的变化趋势。同时，纳米二氧化硅与辐射硫化三元乙丙橡胶的相互作用增强，使得硫化胶的力学性能随着相互作用的加强而得到改善。     

天然微晶纤维素晶须补强天然橡胶的研究

采用硫酸酸解天然微晶纤维素(microcrystalline cellulose,简称MCC)制备纳米微晶纤维素晶须(cellulosewhisker,简称CW),加入天然橡胶胶乳共沉后混炼硫化.结果表明,CW对天然橡胶具有明显的补强作用,经间苯二酚(R)与六亚甲基四胺(H)改性后,NR/RH-CW复合材料的模量、断裂伸长率和撕裂强度都进一步改善.热空气(100℃,72 h)老化后,NR/RH-CW复合材料的力学性能明显优于纯NR,其拉伸强度由28.54 MPa下降至21.78 MPa,变化率缩小至23.7%;断裂伸长率由594%下降至493%,变化率缩小至17.0%,而纯NR的拉伸强度由22.0 MPa下降至2.4 MPa,变化率为89.1%;断裂伸长率由579%下降至168%,变化率为71.0%.扫描电镜分析表明,RH-CW与NR基体的界面相容性较CW改善.热重分析表明,CW的加入使NR的5%失重温度降低,但残重增加,微分曲线在520℃处出现了一个小峰,RH-CW的加入,使该峰变大,残重进一步增加.     

双马来酰亚胺树脂/SiO_2纳米复合材料的制备及性能

以表面含有胺基官能团的纳米SiO_2为填料,通过一步原位聚合法制备双马来酰亚胺树脂/SiO_2纳米复合材料(BMI/SiO_2).采用热重分析仪(TGA)、红外光谱分析仪(FTIR)、邵氏D硬度计(H)等仪器设备对BMI/SiO_2纳米复合材料进行测试分析,探讨纳米SiO_2对双马来酰亚胺聚酯树脂的热稳定性能、硬度和界面强度的影响.结果表明,所制备的BMI/SiO_2纳米复合材料的硬度随加入的纳米SiO_2含量的增加,呈现逐渐升高趋势.当纳米SiO_2含量为3%时,相对于双马来酰亚胺聚酯,复合材料的硬度提高了80%.通过热稳定性分析可知,纳米SiO_2的加入降低了双马来酰亚胺树脂基体材料的热分解温度,使其从458℃降低到451℃.通过对双马来酰亚胺/SiO_2纳米复合材料的界面分析发现,纳米SiO_2的表面接枝了双马来酰亚胺分子链,说明纳米SiO_2参与了双马来酰亚胺的聚合过程,有利于提高聚合物基体材料与填料间的界面强度,进而提高复合材料的机械性能.     

Influence concentration of modifying agent on properties of natural rubber/organoclay nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different concentrations of octadecylamine organic modifying agent at 0.5, 1.0 and 1.5 times the CEC of Na-MMT. Influence of concentration of modifying agent on properties of the organoclays and natural rubber/organoclay nanocomposites was investigated. It was found that the optimum concentration of modifying agent was 1.5 times the CEC of Na-MMT. That is, at this concentration, larger d-spacing of organoclay particles and higher degree of clay dispersion in natural rubber matrix were observed. Larger interlayer d-spacing also caused enhancement of the mechanical properties of the NR/organoclay nanocomposites. Additionally, the NR/organoclay nanocomposites with higher concentration of modifying agent exhibited faster curing reaction with higher crosslink density. Furthermore, the organoclays with larger d-spacing and higher degree of dispersion in the natural rubber matrix exhibited enhancement of the mechanical and dynamic properties and thermal stability of natural rubber/organoclay nanocomposites.     

Multifunctional action of in situ formed Zn-salt of monoallylmaleamic acid

Monoallylmaleamic acid (CH₂=CH-CH”2-NH-CO-CH=CH-CO-OH; MAMA) when used in combination with zinc basic carbonate (ZBC) shows multifunctional action during processing and peroxide curing of hydrogenated nitrile rubber (HNBR). It follows from the lower viscosity, higher crosslinking degree and higher tensile strength of samples prepared from HNBR, MAMA, ZBC and peroxide, compared with the HNBR cured with the peroxide only. This kind of activity of the such system is connected with the in situ formation of very small particles of Zn-MAMA salt dispersed in the rubber matrix and in part chemically bound to the rubber.     

Mechanical properties of carbon black filled hydrogenated acrylonitrile butadiene rubber for packer compounds

Hydrogenated acrylonitrile butadiene rubber (HNBR) was chosen to develop peroxide cured and carbon black N220 (CB) reinforced high modulus vulcanizates with possible applications in packers for oil exploration. HNBR vulcanizates are investigated by Rubber Processing Analyzer RPA 2000 and stress-strain tests conducted both in elongation and compression mode. All the mechanicals properties were tested both at room temperature (RT) and 150 °C in order to reflect application of packers. The results show that the modulus of CB filled HNBR vulcanizates increases with the increase of CB loadings in shear, tensile and compression mode. The physical interactions resulting from CB reinforcements show a stronger temperature-dependence than chemical crosslinks formed by curing agent. So the addition of reinforcing carbon black will have limited benefit for producing packer compounds with high enough modulus at high temperature, but more amount of curing agent will contribute to a stable high enough modulus. It is testified the filler-filler interaction is more temperature dependent than filler-rubber interaction and more chemical crosslinks increase the filler-rubber bonding and slightly decrease the filler-filler interaction, which is confirmed by the reinforcement factors. Compression tests show a strong dependence on the geometry of the samples and the compressive Payne Effect is examined by the multiple compression cycles. It gets stronger as the CB loading is increased.     

Effect of radiation dose on the properties of natural rubber nanocomposite

Effect of radiation dose and carbon nanotubes (CNT) on the mechanical properties of standard Malaysian rubber (SMR) was investigated in this study. SMR nanocomposites containing 1–7 phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200 kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M₁₀₀) were studied as a function of radiation dose. The structure and morphology of reinforced natural rubber was investigated by FESEM, TEM and AFM in order to gain further evidence on the radiation-induced crosslinking. It was found that the Ts, M₁₀₀ and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100 kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation.     

Curing and Physical Properties of Natural Rubber/Wood Flour Composites

Natural rubber based composites were prepared by incorporating Wood flour of two different particle size ranges (250–300 µm) and (300–425 µm) and concentrations (15 and 30 phr) into the matrix, using a Banbury® internal mixer according to a base formulation. Curing characteristics of the samples were studied. Influence of particle size and loading of filler on the properties of the composites was analyzed. Results obtained show that the addition of wood flour to natural rubber increased scorch time and curing time and caused improvement in modulus at 300% strain and in tear properties. However, it decreased tensile strength and elongation at break. The particle size range of 300–425 µm was found to offer the best overall balance of mechanical and dynamic properties (tan δ and viscous torque). Swelling behavior of the composites in toluene was also analyzed in order to determine the rubber volume fraction and crosslinking density. Composites with the bigger particle size wood flour were found to have greater crosslinking density than the ones with smaller particle size, fact that could possibly indicate a better rubber-filler interaction in the former. Major percentage of filler increased slightly this interaction. Water absorption behavior of the composites with wood flour reached a maximum of 12% w/w when 30 phr of filler were incorporated; nonetheless, particle size did not affect this property. The ageing study in presence of air at 70 °C revealed that natural rubber composites with wood flour maintained the same classification cell with temperature as the pure rubber. A compound with 30 phr of carbon black was prepared for comparative purposes. Results obtained were as expected. Scorch time decreased and higher values of modulus at 300% strain and tensile strength were achieved, due to strongest interaction between filler and elastomer.     

丁腈羟平均官能度对固化反应及固化物性能的影响

以过氧化氢为引发剂,加入巯基乙醇或丙烯酸羟乙酯,合成了四种不同官能度的端羟基丁二烯-丙烯腈共聚物。以异佛尔酮二异氰酸酯为固化剂,N,N'-二羟丙基苯胺为链延伸剂,制得一系列多嵌段聚氨酯弹性体,研究了平均官能度对固化反应速度及固化物力学性能、动态力学性能、热性能和耐油性能的影响规律。     

The mechanical properties of a model hydrogenated nitrile butadiene rubber (HNBR) following simulated sweet oil exposure at elevated temperature and pressure

A typical carbon black reinforced hydrogenated nitrile butadiene rubber (HNBR) was exposed to a mix of hydrocarbons (toluene, heptane and cyclohexane) at elevated temperatures and pressure in order to chemically age the material. The effect of this exposure on the mechanical properties is reported; the most significant change is a dramatic increase in tensile stiffness for specimens exposed at 160 °C for 12 weeks. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) revealed changes in the glass transition behaviour of this material, with a general reduction in the magnitude of the glass transition with increasing ageing time. In addition, gravimetric studies of the swollen specimens after removal from the hydrocarbon mix showed that the more aged specimens underwent significantly slower drying rates compared to less aged specimens. These results may be explained by an increase in crosslink density in the materials being the main mechanism occurring during chemical ageing of these HNBR compounds.     

Effect of chitosan derivatives as rubber antioxidants for increasing durability

A series of chitosan derivatives, namely polydiethylamino-ethylmethacrylate-chitosan-graft-copolymer (chitosan-g-DEAEMA), polycarboxy-chitosan-graft copolymer (chitosan-g-COOH), polyvinyl alcohol chitosan-graft-copolymer (chitosan-g-VOH), and carboxymethyl-chitosan (CM-chitosan), were synthesized and investigated as antioxidants for natural rubber (NR) and acrylonitrile butadiene rubber (NBR) mixes and vulcanizates to increase their durability. The rheometric characteristics of the rubber mixes were determined using an oscillating disc rheometer. The physico-mechanical properties of the rubber vulcanized were measured before and after exposure to thermal oxidative aging. It was found that the CM-chitosan had an accelerating effect on the curing process of NR and NBR. Also, the investigated polymers enhanced the properties of rubbers (NR and NBR) especially after ageing up to 7 days compared with commercial antioxidants, such as phenyl ß-naphthylamine (PßN) and N-isopropel-Nphenyl-p-phenylene diamine (IPPD) which are used in the rubber industry. After ageing, the retained values of tensile strength, modulus at 100 % strain, and elongation at break were improved. The optimum concentration of the investigated compounds used to give good properties was found to be 1–2 parts per 100 of rubber (phr). In addition, these prepared polymers showed a decrease in the equilibrium swelling of rubber in toluene which is the proper solvent and consequently increases the crosslink density for rubbers.