Effects of Magnesium Hydroxide on the Flame Retardancy of Ethylene-Vinyl Acetate Copolymers/Nitrile Rubber Blends

The fire-resistant noncorrosive ethylene-vinyl acetate copolymers with vinyl acetate (VA) content > 40 wt.% (EVM)/acrylonitrile-butadiene rubber (NBR)/magnesium hydroxide (MDH) composites were prepared, and the influence of MDH contents on flame retardancy, thermal stability, filler dispersion, and mechanical properties were studied. The flame-retardant effect of three different flame retardants [micro-sized MDH (mMDH), nano-sized MDH (nMDH), and micro-sized aluminum hydroxide (mATH)] was also investigated by cone calorimetry, thermal gravimetric analysis, and rubber process analysis in this paper. The decrease of the heat release rate and total heat release, the increase of residual mass, and the enhancement of thermal stability of the composites were all due to the flame-retardant effect of the MDH. The EVM/NBR vulcanizates had the best flame retardancy when the mMDH content was 180 phr. It was also found that the nMDH, mMDH, and mATH at the same loading had no obvious influence on the limiting oxygen index, while the combustion behaviors measured by the cone calorimeter had significant differences. The addition of ATH prolonged the time to ignition. The mMDH showed a better flame retardancy for EVM/NBR vulcanizates than the nMDH.     

The Effect of Reclaim Softener on Properties of Reclaimed Rubber

The reclaiming process of full tire rubber powder with no treatment was carried out with a torque rheometer. The effect of reclaim softener types and loads on reclaiming and the properties of the revulcanized reclaimed rubber were investigated. The sol fraction significantly increased and the crosslink density gradually decreased with the increase of reclaim softener loads, but the reclaimed rubber with wood tar reclaim softener had the lowest sol fraction and highest crosslink density at the same loads as other reclaim softeners. The types of reclaim softener had almost no influence on the types of scission, but the proportion of main-chain scission increased with the increase of reclaim softener loads. An improvement of processability was observed with the increase of reclaim softener, but it was accompanied by a decrease in tensile strength. Dynamic mechanical properties of the reclaimed rubber were also investigated. The uncured reclaimed rubbers loaded with reclaim softener showed much lower G′values and slightly higher tan δ values than the reclaimed rubber without reclaim softener and the cured reclaimed rubbers showed much lower G′values and slightly lower tan δ values than the blank.     

Measuring the solidification time of silicone rubber using optical inspection technology

A room temperature vulcanization silicone rubber was widely used as the mold making material due to its high elasticity, good heat-resistance and low surface energy. To enhance the efficiency of making the silicone rubber mold, accurately measuring the solidification time is an important issue. This study demonstrated a non-invasive measurement system to measure the solidification time of silicone rubber. The solidification time can be determined rapidly from the thickness of silicone rubber according to the predicted equation. The maximum relative error of the predicted equation is about 8.26%. The temperature rise of the silicone during the solidification process is an important phenomenon to determine the solidification behavior of silicone rubber. The solidification mechanism of silicone rubber mold is demonstrated.     

飞机跑道胶痕的自动识别系统设计与实现

为了减轻机场跑道除胶工作人员的劳动强度,提高除胶工作效率,文章提出了一种基于机器视觉的胶痕自动查找和识别方法,设计了基于ARM单片机控制的图像无线采集和基于PC机控制的图像接收、图像预处理和图像识别系统。文章通过分析预处理后的数据特点,确定了基于细胞神经网络算法的胶痕识别算法,然后在MATLAB仿真环境下确定了该算法的最优模型和参数,最后在Visual C++ 6.0环境下完成了该算法的程序编译,调试并完成了对胶痕的自动识别过程。理论仿真和程序测试的结果证明了文章提出的方法在胶痕自动识别系统中的可行性,也为机场特种设备的无人化和智能化提供了参考。     

氢及其同位素在溴化丁基橡胶中渗透的分子模拟

使用分子动力学(MD)和巨正则蒙特卡罗(GCMC)的方法,对H_2,D_2,T_2在溴化丁基橡胶(BIIR)中的扩散和溶解行为进行了计算模拟,运用自由体积理论探讨了气体分子在聚合物内的扩散机理,并得出气体的运动轨迹。结果表明:对氢及其同位素而言,质量越小,运动速度越快,扩散系数越大,溶解度系数比较接近,渗透系数的模拟值与实验值基本吻合,为提高材料的阻隔性能提供了一定理论基础,同时预测出硫化溴化丁基橡胶对氚水也有较好的阻隔性能。     

金属丝网橡胶压缩力学性能研究

对金属丝网橡胶进行了静态压缩试验。利用控制变量法研究了压缩量、相对密度、金属丝丝径、丝材和承压面积对金属丝网橡胶压缩力学性能的影响,并对平均刚度和能量耗散系数随压缩量和相对密度的变化关系进行了研究。试验结果表明:随着压缩量的增加,金属丝网橡胶非线性力学特性逐渐增强;相对密度越大,金属丝网橡胶承压能力越强;金属丝的丝径和丝材主要影响金属丝网橡胶非线性阶段的力学特性,丝径越大,丝材越硬,承压能力越强;承压面积越大,金属丝网橡胶的承压和耗能性能越好;随着压缩量的增加,平均刚度增大,承压能力增强,能量耗散系数减小,减震性能降低;随着相对密度的增加,平均刚度和能量耗散系数均增大,承压能力和减震性能均增强。     

The abnormal behavior of polymers glass transition temperature increase and its mechanism

In terms of the classical theory in textbooks, the two components with phase separation in a binary polymer blend will, depending on their compatibility, have their respective Tg get closer or remain in their original values. According to the classical theory, the Tg of plastic component shall remain unchanged or move toward the lower Tg of rubber component in a rubber/plastic blend. However, ultra-fine full-vulcanized powdered rubber (UFPR) with a diameter of ca. 100 nm can simultaneously increase the toughness and the Tg of plastics, which is abnormal and is difficult to explain by classical theory. In this feature article, the abnormal behavior and its mechanism are discussed in detail.     

采用ATRP合成天然橡胶接枝共聚物——Ⅰ. ATRP大分子引发剂的制备

通过环氧化反应在天然橡胶分子链上引入环氧基制得环氧化天然橡胶(2);利用环氧基的反应活性,2与2-溴-2-甲基丙酸发生开环反应合成了原子转移自由基聚合(ATRP)大分子引发剂——天然橡胶-g-(2-溴-2-甲基丙酸),其结构经1H NMR和IR表征.     

采用ATRP合成天然橡胶接枝共聚物——Ⅲ.NR-g-PMMA的制备

N-溴代丁二酰亚胺与天然橡胶(NR)反应合成了大分子引发剂——溴代天然橡胶[NR-Br(1)].通过原子转移自由基聚合(ATRP),以CuBr/PMDTA为催化体系,1引发甲基丙烯酸甲酯(MMA)接枝共聚制得新型天然橡胶-g-聚甲基丙烯酸甲酯[NR-g-PMMA(2)],其结构经1H NMR和IR表征.初步聚合反应动力学研究结果表明,NBS与NR在高温下反应容易伴随双键加成和环化反应,于室温反应所得1具有较高的引发活性;接枝聚合符合一级动力学反应,即2的分子量随MMA单体转化率的提高而增加.     

遥爪型液体天然橡胶的合成与表征

以天然橡胶(NR)为原料,经环氧化反应在NR分子链上引入环氧基制得环氧化天然橡胶(1);1经裂解反应合成了端羰基液体天然橡胶(2);对2进行改性得到端羟基液体天然橡胶(3),其结构经1H NMR和IR表征。探讨了反应温度、时间、氧化剂用量和环氧化程度对2的黏均分子量(M珚η)的影响。结果表明,延长反应时间、升高温度和增加氧化剂用量均可有效降低2的M珚η;1的环氧化程度对2的M珚η具有决定性作用,可通过调节环氧化程度实现2的M珚η的可控性。