Compósitos poliméricos com resíduo de açaí para mitigação de efeitos térmicos como estratégias eco-alternativas em habitações na Amazônia

Abstract

Amazonas state capital is located in a bioclimatic zone where cross ventilation and the use of air conditioning are necessary strategies for achieving the desired comfort. In Manaus, thermal discomfort originated from high temperatures and relative air humidity is present for most of the year. When assessing urban built-up areas in terms of external coating, the building's roof is often one of the main responsible for the thermal load gain, requiring design strategies which support elements capable of attenuating heat. In addition to these thermal mitigators, the bulk of agroindustrial waste is presented as a business opportunity for the construction industry as a sustainable material, with the açaí stone as an example, which is discarded in cities as Belém and Manaus. The present work is aimed at testing polymeric composites from castor oil based bicomponent resin reinforced with açaí stone particulates for mitigating the thermal effects on Amazon households. In order to perform this work, waste supply data was surveyed and posterior collection of material in small processing companies was performed for characterizing the composites' physical, morphological and thermal properties. The results demonstrated that only in 2015, more than 13,000 tons of açaí were produced in the Amazonas state and its stone represents about 80 percent of the fruit, being disposed as waste. Research indicates that the organic residue from açaí does not have high added value, being often allocated for firing in ovens or for composting. The sheet production process began with drying of the stones, oven treatment for posterior milling in a cutting mill and sieving in five screen types for grain size tests. The composites were produced according to an experimental design with a central point, taking into account 3 resin amounts: 10, 12.5 and 15%. This way, 5 types of sheets were obtained, denominated Thick 15%, Thick 10%, Mixed 1, 2 and 3; 12.5%, Medium 15% and Medium 10%. Thick 15% type sheets provided better swelling and water absorption results, important items with regard to the panels dimensional variations. The thermography results also pointed this type of sheet as the most suitable for use in ceiling headliners and partitions due to its potential for thermal comfort. These results indicate that the sheets possess a high potential for sustainable use since they contain raw products from renewable sources, as in the case of castor for the resin and the açaí stone for the reinforcement, mitigating the açaí environmental waste footprint as well as the one for the prepolymer, which accounts for only 7,5% of the sheet composition. The conclusion is that the sheets provide an important environmental benefit, mitigating residues and promoting thermal comfort in housing as well as indicating new valuation elements for açaí, integrating knowledge from Civil Construction, Architecture and Agrometeorology in accord with the public policies for sustainable cities in the Amazon.