纳米CaCO_3的改性、表面结构与流变行为研究

Modification,Surface Structure and Rheological Behavior of Nanosized CaCO_3

采用铝锆偶联剂和棕榈酸改性纳米CaCO3粉体.借助XRD,FTIR,接触角及流变学等测试方法对纳米CaCO3的表面结构进行表征.XRD分析表明:改性纳米CaCO3保持原样品完整的体相结构,为方解石型纳米微晶.FTIR分析证明:表面改性剂与纳米CaCO3表面是以化学键合和物理吸附方式相结合,粒子表面存在羧基等有机官能团的红外吸收特征.通过测定苯和水在改性纳米CaCO3粉末压片上的接触角,计算了改性纳米CaCO3的表面能和极性分量,并与未改性纳米CaCO3进行比较.结果表明,经表面改性,纳米CaCO3的表面能和极性分量明显降低,其在有机溶液中的吸附功增大,界面张力大大降低;经棕榈酸改性的纳米CaCO3表现出较好的亲油疏水性,而铝锆偶联剂改性的纳米CaCO3同时具有亲水性和亲油性.以液体石蜡为溶剂,研究了表面改性对纳米CaCO3悬浮液流变行为的影响.实验发现:经过表面处理,纳米CaCO3粉体悬浮液流变行为发生较大的变化,稳态剪切黏度大大降低,表现出较小的动态弹性储能模量和黏性损耗模量,而损耗因子较大.

Surface modification of nanosized CaCO3 with zircoaluminate coupling agent and palmitic acid was carded out. The surface structure of prepared samples was characterized by XRD, FTIR, contact angle and rheological behavior determination. It was confirmed by XRD that the modified nanosized CaCO3 samples kept the same bulk structure as unmodified CaCO3. According to the spectra of FTIR, it was inferred that chemical binding and physical adsorption between surface modifiers and the nanosized CaCO3 had happened during the modification reaction. The surface free energies and polar components of the nanosized CaCO3 modified with zircoaluminate coupling agent and palmitic acid were calculated by measuring contact angles for water and benzene on the palletized surfaces. It was found that the surface energies and polar components of the nanosized CaCO3 modified with palmitic acid were lower than those of the nanosized CaCO3 modified with zircoaluminate coupling agent, and the contact angle for water on the surfaces of unmodified nanosized CaCO3, nanosized CaCO3 modified with zircoaluminate coupling agent and the nanosized CaCO3 modified with palmitic acid were 0°, 40° and 104°, respectively. It was confirmed that the nanosized CaCO3 modified with palmitic acid was of intense lipophilicity, while the nanosized CaCO3 modified with zircoaluminate coupling agent was of both hydrophilicity and lipophilicity. The rheological behavior of the suspensions composed of the unmodified and modified nanosized CaCO3 with paraffin was compared. The results showed that the apparent viscosity, dynamic elastic storage modulus and viscid loss modulus of the modified nanosized CaCO3 suspension were lower than those of the unmodified nanosized CaCO3 suspension, while the loss factor was higher.