ASSUNÇÃO, L. M. C.; ASSUNÇÃO, Lígia Maria Campos.
Resumo:
Pyroexpansion and mineralogical characterization assays were performed in seven vermiculite samples from different localities of Northeastern Brazil. The "degree of exfoliation" was evaluated by measuring the apparent specific mass and the increase in plate thickness. The first test cited was performed on samples with different particle size (Tyler sieves): above 1/2 "between 1/2" and / 4 ", between 1/4" and # 6, between # 6 and # 14, between # 14 and # 28 and below # 28, at temperatures of 600 ° C '700 ° C, 800 ° C, 900 ° C and 1000 ° C and oven residence times of 3 min., 5 min., 8 min and 10 min The increase in thickness was determined for three large plate samples The "degree of exfoliation" was found to be dependent on the diameter and thickness of the vermiculite plates and the temperature of the assay and reached values within the range. piroexpandados commercial products, for four of the samples tested.The mineralogical characterization used, among others: chemical analysis, cation exchange capacity, differential thermal analysis and x-ray diffraction analysis. air-dried samples treated with ethylene glycol, heated to 550 ° C and treated with MgCl 2. The presence of vermiculite was found in all seven samples studied, sometimes in mixture, sometimes interratified with other minerals such as mica, chlorite and talc.
