Influence of thermal treatment of eucalyptus fibers on the physical-mechanical properties of extruded fiber-cement composites

Abstract

This study proposes to evaluate the effect of the heat treatment in commercial eucalyptus fibers (produced by thermo-mechanical process) on the physical-mechanical properties of extruded fiber-cements composites. The fibers were treated with different temperatures of heat treatment (140, 170, 200 and 230 °C) for 60 min in a “Macro-ATG” oven. The chemical and morphological characteristics of the natural fibers were evaluated before and after the thermal treatment. The cementitious paste was composed by 67.9% cement, 29.1% limestone and 3% eucalyptus fibers. Hydroxypropylmethylcellulose (HPMC) and polyether carboxylic acid (ADVA 175) were added to the cement paste both in 1% (based on the cement mass) to facilitate the extrusion process. The thermal treatments at 200 and 230 °C were efficient in reducing the extractives content. On the other hand, a decrease in length, diameter and lumen size of the fibers has occurred. The decrease in extractives content did not influence the properties of water absorption, modulus of rupture (MOR) and modulus of elasticity (MOE). The increase in lignin content resulted in increase for apparent porosity and decrease of the toughness in reinforced fiber-cement produced with fibers treated at 200 and 230 °C. The application of the thermal treatment for the fibers did not show improvement in fiber-cement in the evaluated conditions. It is recommended to evaluate other properties of the fiber-cement reinforced with the mentioned treated fibers, such as natural and laboratorial weathering.