The influence of density on the mechanical response of reinforced high-density polyurethane foams : a statistical approach

Abstract

In this work,rigid polyurethane foams(RPUF)reinforced bymicrofibrillated cellulose (MFC) were manufactured usingthe freerising method and also under confinement inside a closed mould, aiming to increase apparent densityand improvemechanical response. Neat RPUF were also manufactured for comparison.The mechanical response, evaluated by compression (following ASTMD1621 standard) tests were correlated with the final composite apparent density (evaluated following ASTM D1622standard). Simple linear regression statistical models, based onF-test, were developed using stat graphics software, aiming to understand and correlatethe increment in densityand its influence on the improvement in mechanical response. Different models were developed to describe the foam behavior. The mainresults showa more significant influence of the density onstrength thanstiffnessfor the neat RPUF, unlike the MFC-reinforced RPUF, which presented an oppositeresponse. These effects couldbe caused by the lowercontent of voids whenthe foams were produced under confinement, and bythe greater crosslinkdensity, when MFC was added.