A novel vermiculite/ vegetable polyurethane resin-composite for thermal insulation eco-brick production

Affordable houses with thermal insulation materials are an efficient and creative solution for needy populations in regions where high temperatures are a public health and economic problem. In this sense, the present work had as objective to present, produce, and evaluate composites of raw vermiculite (RV) or expanded vermiculite (EV) in a vegetable polyurethane resin (VPR) matrix as thermal insulation eco-bricks. First, RV and EV were characterized by thermogravimetry (TG/DTG), X-ray fluorescence spectrometry (XRF), and scanning electron microscopy (SEM) coupled to energy-dispersive X-ray spectroscopy (EDX). Second, VPR was analyzed by TG/ DTG. Then, materials were mixed and conformed into bricks in concentrations of 70, 80, and 90 wt % of raw vermiculite, and also 70, 80, 90 wt % of expanded vermiculite. The produced bricks were submitted to an alterability test with immersion into chemical reagents (ASTM D 543), humid atmosphere attack (NBR 8095), UV exposure (ASTM G 53), compressive test (ASTM D 695), physical indexes (NBR 12766), thermal insulation test, and TG/flammability test (ASTM D 635). Analysis of Variance (ANOVA) derived by a mixed 2 and 3-level design was utilized. Only 70% raw vermiculite passed NBR 8492 (soil-cement brick - dimensional analysis, compressive strength determination and water absorption - test method) and for this reason, was chosen for prototype production. Vermiculite react more with acid solutions. Vermiculite incorporation improves thermal stability and flame retardancy. 70 wt % RV brick was able to reduce 65% of the temperature, with good compressive strength (4.12 MPa) and low specific mass (1.47 g cm-3).