Painel reconstituído a partir do sisal (agave sisalana) para isolamento térmico de edificações

Abstract

Constructions in the Brazilian semi-arid region are subject to great seasonal temperature variability, which implies unfavorable conditions in housing in this region in terms of thermal performance. At the same time, the use of technologies aimed at the thermal comfort of homes has drawbacks in terms of application, from the consumption of non-renewable raw materials to the emission of polluting gases that are harmful to human health. The sisal inflorescence is a by-product of Agave sisalana, a species exploited in the sisal region for fiber production. However, the inflorescence is an underestimated residue, found in large quantities in the sisal region and which, according to the bibliography, as a lignocellulosic material, could be converted into a reconstituted panel, Allied to this, the low thermal conductivity of cellulose would make the generated panel a thermal insulating solution for buildings, with less environmental impact, especially constructions in the semi-arid region. This work aims to develop and analyze a reconstituted material produced with the sisal inflorescence and polyurethane castor based resin, considering the potential of lignocellulosic materials in terms of thermal insulation capacity and the favorable reconstitution process. The sisal inflorescences were physically characterized using NBR 7190 (ABNT, 1997); Inflorescence microstructure, chemical composition and thermal degradation were also analyzed. The reconstitution of the panels was made from the crushed sisal inflorescence and the use of castor based polyurethane resin; the reconstituted material was classified according to the bibliography and NBR 14810 (ABNT, 2002), which was also the guideline for physical and mechanical tests on the material developed. The determination of the material's thermal conductivity was performed by the protected hot plate method, using NBR 15220 (ABNT, 2005). The evaluation of the thermal insulating capacity was performed using the calorimeter method. The degree of biological degradation, by termite attack, and the flammability of the panel were also verified by UL 94 V and H (Underwriters Laboratories Inc., 1998). The results found are in agreement with reconstituted materials observed in the literature review; The thermal degradation analyzes demonstrate the stability of the raw material for use as residential thermal insulator as the degradation analysis for temperatures below 200 ºC; The physical characteristics of the material such as swelling thickness and water absorption are higher than the results found in references, however the density and humidity remained within the limits of the review; The panels produced with inflorescence core and content of 10% of castor resin and pressing tension of 2 MPa showed greater dimensional stability after curing; The physical and mechanical characteristics of the panels are compatible with the classification of the developed insulator; The thermal insulation capacity verified was higher than the materials commonly used in constructions; The thermal conductivity coefficient of the developed panel had a better performance compared to vegetal and synthetic thermal insulation materials. The panels with 3 layers of 10 mm each had 0.0251 W/m.k and the panel with a single layer of 30 mm had 0.0243 W/m.k; these results classify the panel as a good thermal insulator. The biological degradation by soil termites of the Nasutitermes corniger species, observed less interests for panel consumption than in relation to the sisal bloom stalk in natura, which was 17.9% higher. For thermal degradation by fire, it showed self-extinguishing capacity for horizontal burning, however for vertical burning the fire had consumed the specimen till the holding clip, with a velocity of burning of 175.47 mm/minute. The found results indicates the potential of using sisal bloom stalk panels in order to thermal insulation applicability for residential purpose