Research On Vermiculite Expansion Characteristics And The Determination Method Of Vermiculite Expansion Ratio

Exfoliated vermiculite is an excellent thermal and acoustic insulated environment-friendly and energy-saving material, with the characters of fire-resistant, corrosion-resistant and freeze-resistant, which can be applied very widely. There's abundant of vermiculite mineral resources in our country, but the expansion mechanism of vermiculite is not clear, without a corresponding expansion rate determination, the development and utilization has many problems such as less product variety, simple rough expansion process, low utilization of fine particle vermiculite compared with foreign countries.To study the mechanism of expansion, using the industrial vermiculite from lingshou of hebei as experimental material, characterized it with X-ray spectrum analysis, infrared spectroscopy and X-ray diffraction analysis, and studied the structural feature and expansion characteristics of vermiculite. It revealed that the raw material mainly composed of vermiculite and hydrobiotite, dehydrating as the temperature increases gradually. Vermiculite lost interlayer water forming a"talc layer"structure till 500℃, and the volume of vermiculite expanded apparently. However, when the temperature reached 900℃, the Si-O tetrahedron structure was destroyed, thereby affecting the expansion property of vermiculite.Analyzing the tapies of cation in industrial vermiculite by X-ray energy dispersive spectrometer, the cation exchange capacity(CEC) of vermiculite was 55.6mmol/100g measured by ammonium chloride-ethanol method. The vermiculite was modified by different concentrations of sulfuric acid, sodium carbonate, and hexadecyl trimethyl ammonium bromide. The results indicated that the CEC of acidized vermiculite,Na-modified vermiculite,organo-intercalated vermiculite increased to 73.5mmol/100g,60.2mmol/100g and 68.8mmol/100g, respectively.Aiming at the current situation that there is no uniform standard for the determination of vermiculite expansion ratio, the measuring methods were discussed respectively from individual and cumulative volume expansion ratios, according to the comparison and analysis, we got the advantages and limitations of existing measuring methods of vermiculite expansion ratio. Finally, based on microstructure of vermiculite, this paper put forward a new method to characterize quality of expanded vermiculite, using the BET specific area and pore radius of vermiculite tested by Accelerated Surface Area and Porosimetry (ASAP) to ascertained the vermiculite expansion ratio.The traditional vermiculite expansion process was thermal exfoliated by fuel or electricity. With the development of vermiculite technology, the main process at present was microwave exfoliated and chemical exfoliated. The main factors affecting vermiculite expansion ratio were size, heating temperature, heating time and modified condition, the orthogonal experiment indicated that the optimum processing conditions were: the size was 1-2mm, hydrogen peroxide was 20%, heating temperature was 700℃, heating time was 60s. It could further accelerate the exploitation and application of the environment-friendly and energy-saving materials with the in-depth study of vermiculite processing.