胶粉在改性沥青中的物化行为分析

Analysis of Physical and Chemical Behavior of Crumb Rubber in Asphalt

生产胶粉改性沥青(CRMA)是实现废橡胶资源化利用及减轻环境污染的有效途径。为了研究胶粉在沥青中的物理及化学行为,采用邻苯二甲酸二丁酯(DBP)模拟沥青的轻组分,将胶粉置入DBP中,在175℃下,反应1.5 h后分离胶粉与轻组分,对轻组分进行气相色谱与质谱联用(GC-MS)分析,讨论胶粉与轻组分发生的物理化学作用;对不同条件下制备的胶粉改性沥青分离胶粉后进行红外光谱(IR)和差示扫描量热(DSC)分析,研究橡胶改性沥青中的官能团变化和热力学特性。结果表明,分离胶粉后的DBP中存在19种检出物,除含量最高的DBP外,其余物质均为胶粉浸出物或与轻组分的反应产物,即胶粉在轻组分中发生了复杂的物理化学反应。胶粉沥青样品中的—CH_2和C=C双键等特征官能团吸收峰大幅增强,橡胶分子在沥青中发生断链降解释放出小分子物质溶于沥青组分发挥改性作用;195℃、1.5 h和175℃、3.0 h制备的沥青样品DSC谱线出现了强烈的吸热峰,即处理温度过高或时间过长,可能发生胶粉过度降解、胶粉团聚或沥青老化行为,使胶粉改性沥青的物化状态发生改变,导致性能劣化。从胶粉物化变化的角度,建议制备胶粉改性沥青时,胶粉掺量(质量分数)应在20%左右,处理温度不高于195℃,处理时间不超过1.5 h。

Preparation of crumb rubber modified asphalt（CRMA） is an＇effective way to recycle waste rubber and to reduce environmental pollution, To study the physical and chemical behavior of crumb rubber in asphalt, dibutylphthalate（DBP） is used to simulate the light components of asphalt. The reaction time is 1.5 h at 175℃ after crumb rubber is stirred into the DBP. The light components are separated from crumb rubber. The physical and chemical effects of crumb rubber in the light components, are investigated by gas chromatography-mass spectrometry （GC-MS） analysis of the separated light component. To study functional group changes and thermodynamic properties of rubber modified asphalt, CRMAs were respectively prepared under conditions of different temperature and treating time. Infrared spectra （IR） and differential scanning calorimetry（ DSC ） tests were then conducted on asphalt samples after removing crumb rubber by sieving method. The results indicate that 19 kinds of substances are detected in separated light components. In addition to the highest contents of DBP, the others are speculated to be all the materials from crumb rubber or the products from the complex physical and chemical reactions between crumb rubber and the light components. The absorption peaks of typical functional groups --CH2 and C==C increase significantly, which fully proves that the molecular chains of rubber rupture and release small molecule materials dissolved into asphalt playing a role of asphalt modification. The strong endothermic peaks of DSC curve appear for asphalt samples prepared at 195℃, 1.5 h and 175℃, 3.0 h. Therefore, the processing conditions such as high temperature and long time may lead to excessive degradation or aggregation of crumb rubber as well as asphalt aging, which change the physical and chemical properties and performances of CRMA. The production conditions of CRMA are recommended that the dosage of crumb rubber is 20% approximately, at a temperature less than 195℃ and the treating time less than 1.5 h.