Modificação superficial da celulose visando o aumento da durabilidade de compósitos à base de cimento

Abstract

Increasing researches to increase the useful life of asbestos composites in order to meet the minimum durability requirements of the final product is of great importance, since they have a fragile mechanical behavior and can present cracks when exposed to traction. The objective of this study was to evaluate the physical-mechanical performance and the durability of extruded asbestos composites produced with surface-modified cellulose pulp from latex and polyurethane castor oil. The following concentrations were used for the chemical modification of the fibers: 5, 10, 15, 20 and 25% of latex and polyurethane of castor oil in relation to the dry mass of the cellulose pulps. The composites were produced in laboratory scale by extrusion. The formulation used was 5% cellulose pulp, 60% Portland cement (CPV-ARI), 33% crushed agricultural limestone, 1% hydroxypropylmethylcellulose (HPMC) and 1% polyester carboxylic additive (ADVA) and final water / cement ratio of 0.4. The mechanical, physical and microstructural properties were determined before and after the accelerated aging test. It was observed that the coating of the cellulose with latex resulted in a decrease in the mechanical strength of the fiber-cement. However, for the 20% concentration of latex, there was a decrease in the hydrophilicity of the cellulose pulp and an improvement of the physical properties of the fiber, providing greater protection after aging. The use of castor-based polyurethane to coat the cellulose provided an improvement in the physical properties, but a reduction in the mechanical properties of the composites after 28 days of cure. However, after the aging cycles, the superficial modification of the pulps with Polyureatana de Manona (PUR) showed to be promising for the maintenance of cellulose fiber properties in the cement matrix.