基于SEM与FTIR研究改性钢渣/橡胶复合材料的热氧老化机理

钢渣是冶金工业中产生的主要固体废弃物，其产量约为每年粗钢产量的15%~20%。由于技术的局限，导致我国钢渣利用率较低，仅为年钢渣产量的10%，同时加之管理制度的不健全，导致钢渣大量露天堆放，对土地资源、地下水源，以及空气质量形成严重影响。面对上述问题，以热闷渣、电炉渣和风淬渣研发改性钢渣微粉，并且将改性钢渣微粉与复合橡胶进行复合制备改性钢渣/橡胶复合材料。依据《硫化橡胶或热塑性橡胶热空气加速老化和耐热试验》（GB/T3512—2014）对改性钢渣/橡胶复合材料进行热氧老化处理，采用平衡溶胀法测定改性钢渣/橡胶复合材料的交联密度，扫描电子显微镜（SEM）、热重分析仪（TGA）和傅里叶转换红外光谱仪（FTIR）分别测试其微观形貌、失重率和结构组成，从微观层面阐述改性钢渣/橡胶复合材料的热氧老化机理。结果表明在热氧老化前期老化作用在改性钢渣/橡胶复合材料表面，其内部以交联键形成反应为主；在热氧老化中期老化作用已经作用改性钢渣/橡胶复合材料内部，造成交联键断裂反应速度高于交联键形成反应速度，形成大量断裂交联键；在热氧老化后期由于改性钢渣/橡胶复合材料内部已经存在大量断裂交联键，导致主链及交联键断裂速度降低，交联键形成反应占优势。改性钢渣微粉以热闷渣（SiO₂含量高）为原材料，有利于形成聚合物大分子链贯穿炭黑网络的结构，提高综合性能，尤其是物理机械性与滞后性；以电炉渣、风淬渣（Fe₂O₃含量高）制备改性钢渣微粉，有利于热传导性能的改善，不仅提高改性钢渣/橡胶复合材料的耐热性，而且提高其硬度与脆性。热氧老化过程中改性钢渣/橡胶复合材料内部在橡胶分子链α-H上发生了不同程度的氧化反应，并在橡胶分子链周围生成了羟基、羧基和醇类化合物，双键烯氢含量降低。

Thermal Oxidative Aging Mechanism of Modified Steel Slag/Rubber Composites Based on SEM and FTIR

Steel slag tailings are the main solid waste in the metallurgical industry, with the production of 15%~20% of crude steel. Due to limited technology, the utilization ratio is quite low and only reaches 10% of steel slag tailings production. Meanwhile, steel slag tailings are disposed of in direct stacking and landfill since the management system is not perfect, which pollutes land, underground water, and air quality. In the face of the above problems, in this study, the modified steel slag powder was developed by hot slag, electric furnace slag and air quenching slag, and the modified steel slag powder was compounded with composite rubber to prepare modified steel slag/rubber composites. According to the “Accelerated aging and heat resistance test of vulcanized rubber or thermoplastic rubber in hot air” (GB/T3512—2014), the modified steel slag/rubber composites were subjected to thermo-oxidative aging treatment. The cross-linking density of the modified steel slag/rubber composites was determined by the equilibrium swelling method. The microstructure, weight loss rate and structural composition of the modified steel slag/rubber composites were tested by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), and Fourier transform infrared spectrometer (FTIR), respectively. The thermo-oxidative aging mechanism of the modified steel slag/rubber composites was expounded from the micro level. The results show that the cross-linked bond formation reaction is the main reaction in the surface of modified steel slag/rubber composites during the early thermal-oxidative aging. In the middle stage of thermo-oxidative aging, the aging effect has acted on the internal of modified steel slag/rubber composites, resulting in the fracture reaction rate of cross-linking bonds higher than that of forming a large number of broken cross-linking bonds. In the later stage of thermal-oxidative aging, many broken cross-linked bonds have been formed in the modified steel slag/rubber composites, resulting in the decrease of the fracture speed of the main chain and cross-linked bonds and the formation of cross-linked bonds is dominant. The modified steel slag powder with high SiO₂ content as raw material is beneficial to form the structure of polymer macromolecular chain through carbon black network and improves the comprehensive performance, especially the physical and mechanical properties and hysteresis. Preparation of modified steel slag powder with electric furnace slag and air quenching slag (high Fe₂O₃ content) is beneficial to improving heat conduction performance.