Preparation And Properties Of CaCO₃/SiO₂/NH₂/PANI Conductivity Composite Powders

CaCO₃, as an important inorganic filler, is widely used in various fields such as rubber, plastics, paper making and coatings due to low cost, excellent performance and non-poisonous. Despite such attractive properties, the poor conductivity of CaCO₃ significantly limits its application in various materials. One method for overcoming this problem is by preparing its composite with conducting polymers. In this paper, CaCO₃ was firstly modified by TEOS and KH550. Then, polyaniline?PANI? was synthesized on the surface of the CaCO₃/SiO₂/NH₂ composites, resulting the formation of core-shell composites of CaCO₃/SiO₂/NH₂/PANI. The morphology, structure and conductivity of the CaCO₃/SiO₂/NH₂/PANI composite particles is characterized by XRD, TEM, FTIR,TGA and four probe method.CaCO₃ was prepared by multi-decomposed method. Then, we used Sol-Gel method, where TEOS was used as the precursor of SiO₂, ammonia as the catalyst,ethanol as co-solvent, to do research on the technique of coating modification of CaCO₃.The results indicated that when the reaction temperature was in 45 oC, the concentration of TEOS and proportion of Vethanol:VH₂O were 0.6 mol/L and 8:2, it successful coated a close shell of SiO₂ onto CaCO₃ core. The as-prepared CaCO₃/SiO₂ has a core-shell structure, and coating with SiO₂ don not change the morphology and structure of CaCO₃.However, coating with SiO₂ layer improves the acid resistance of CaCO₃. The CaCO₃ is uniformly coated by SiO₂ through the chemical bonds of Ca-O-Si.KH550 was used to modified the surface of CaCO₃/SiO₂ composites. The CaCO₃/SiO₂/NH₂ shows highest activation rate when content of KH550 was 2.5%. The immobilization of KH550 on the surface of CaCO₃/SiO₂ further improved the acid resistance of the CaCO₃.In the preparation process of CaCO₃/SiO₂/NH₂/PANI via a in situ polymerization,CaCO₃/SiO₂/NH₂ was used as the raw materials, ammonium peroxydisulfate and HCl were used as the initiation and dopant, respectively. The best condition for preparing of CaCO₃/SiO₂/NH₂/PANI as follows: The volume ratio of ethanol to water was 7:0, the mass ratio was was 1.5:1, and the concentration of HCl was 0.6 mol/L. Under the condition of the process, CaCO₃/SiO₂/NH₂ was well covered by the PANI. Compared with the pristine PANI, the CaCO₃/SiO₂/NH₂/PANI composites showed much better thermal stability.