The role of nanocrystalline cellulose on the microstructure of foamed castor-oil polyurethane nanocomposites

A. I. CORDERO; J.I. AMALVY; E. FORTUNATI; J. M. KENNY; L. CHIACCHIARELLI

CARBOHYDRATE POLYMERS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2015 vol. 134 p. 110 - 118

0144-8617

tNanocrystalline cellulose (CNC), obtained by sulphuric acid hydrolysis, was used to synthesizepolyurethane foams (PUFs) based on a functionalized castor oil polyol and a Methylene diphenyl diiso-cyanate (MDI). Formulations with varying isocyanate index (FI) and NCO number were prepared. At0.5 wt.%, SEM?s of the fractured surface underlined that the CNC acted both as a nucleation agent andas a particulate surfactant with cell geometries and apparent density changing selectively. The chemicalstructure of the PUF (FTIR) changed after the incorporation of CNC by a relative change of the amountof urea, urethane and isocyanurate groups. A low NCO number and isocyanate index contributed to themigration of the CNC to the Hard Segment (HS), acting as reinforcement and improving substantially thecompressive mechanical properties (Ecand cimprovements of 63 and 50%, respectively). For a high NCOnumber or isocyanate index, the CNC migrated to the Soft Segment (SS), without causing a reinforcementeffect. The migration of the CNC was also detected with DSC, TGA and DMA, furtherly supporting thehypothesis that a low NCO number and index contributed both to the formation of a microstructure witha higher content of urethane groups.