SÃntese e caracterizaÃÃo de hidrogÃis compÃsitos superabsorventes a base de poliacrilamida e vermiculita.

• Autor(a) principal: Ana Paula Dantas de Lima
• Data de Publicação: 2008
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFC
• Texto Completo: http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8511
• topic: Vermiculita; Poliacrilamida; HidrogÃis; QUIMICA

Hydrogels composites of polyacry lamide and hydrogels based on polyacry lamide and vermiculite (PAM/VMT) were synthesized through polymerization reaction i n solution. Organophilic clay was obtained from the cationic exchange reaction with a quaternary ammonium salt. From the modified clay, PAM/VMT was also synthesized. A series of hydrogels were obtained by varying the percentage of clay in relation to the m onomer (5, 10, 20 and 30%) and the crosslinking content added (0.05, 0.1 and 0.2 mol %) to the reaction medium. The hydrogels were characterized by spectroscopy in the infrared region (FTIR), thermogravimetric analysis (TGA), elemental analysis, dynamic rh eology, X - rays and scanning electron microscopy (SEM), absorbance measurements in water, salty environment and variations of pH. The X - rays diffractogram belonging to the organophilic clay demonstrated a displacement of the basal spacing in relation to the non modified clay. In addition to this, typical Infrared bands of the alkyl radical were found. The polyacry lamide and polyac ry lamide/vermiculite hydrogels presented low water ab sorbance capacity values (30 - 35 g H 2 O/g gel). A Fick behaviour was observed fo r the dynamic sorption of hydrogels. Hydrogels with superabsorbent characteristics (Weq > 1000 H 2 O/g gel) were obtained after hydrolysis with NaOH. The capacity of absorbance of water by the hydrogels was increased with the decrease on the concentration of crosslinker and higher W eq values, (swelling in the equilibrium) were observed. The hydrogels showed to be sensitive to the pH variation and to the presence of salts. The hydrogels, even though submitted through a cycle of drying and swelling, conserved t heir superabsorbent characteristics. The rheological behaviour observed is a characteristic of strong gels. The PAM gel with 10% of clay presented higher Gâ a nd Gâ values. The synthesized hydrogels demonstrated better water absorbance properties when c ompa red with commercial polyacry lamide gel.