title: The role of nanocrystalline cellulose on the microstructure of foamed castor-oil polyurethane nanocomposites.
abstract: Nanocrystalline cellulose (CNC), obtained by sulphuric acid hydrolysis, was used to synthesize polyurethane foams (PUFs) based on a functionalized castor oil polyol and a Methylene diphenyl diisocyanate (MDI). Formulations with varying isocyanate index (FI) and NCO number were prepared. At 0.5 wt.%, SEM's of the fractured surface underlined that the CNC acted both as a nucleation agent and as a particulate surfactant with cell geometries and apparent density changing selectively. The chemical structure of the PUF (FTIR) changed after the incorporation of CNC by a relative change of the amount of urea, urethane and isocyanurate groups. A low NCO number and isocyanate index contributed to the migration of the CNC to the Hard Segment (HS), acting as reinforcement and improving substantially the compressive mechanical properties (Ec and σc improvements of 63 and 50%, respectively). For a high NCO number or isocyanate index, the CNC migrated to the Soft Segment (SS), without causing a reinforcement effect. The migration of the CNC was also detected with DSC, TGA and DMA, furtherly supporting the hypothesis that a low NCO number and index contributed both to the formation of a microstructure with a higher content of urethane groups.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT La Plata CONICET-UNLP, Diag. 113 y 64, La Plata, Argentina.
authors.forename: Andrés Ignacio
authors.initials: AI
authors.lastname: Cordero
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), CCT La Plata CONICET-UNLP, Diag. 113 y 64, La Plata, Argentina.
authors.forename: Javier Ignacio
authors.initials: JI
authors.lastname: Amalvy
authors.affiliation: Materials Engineering Center, UdR INSTM, University of Perugia, Strada di Pentima 4 05100 Terni, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Fortunati
authors.affiliation: Materials Engineering Center, UdR INSTM, University of Perugia, Strada di Pentima 4 05100 Terni, Italy.
authors.forename: José María
authors.initials: JM
authors.lastname: Kenny
authors.affiliation: Instituto de Tecnología de Polímeros y Nanotecnología (ITPN), CONICET-UBA, Buenos Aires, Argentina. Electronic address: lmchiacchiarelli@yahoo.com.ar.
authors.forename: Leonel Matías
authors.initials: LM
authors.lastname: Chiacchiarelli
mesh_terms: D002368:Castor Oil / Q000138:chemical synthesis / Q000737:chemistry*; D055119:Elastic Modulus; D017953:Isocyanates / Q000138:chemical synthesis / Q000737:chemistry; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure*; D053758:Nanoparticles / Q000737:chemistry*; D011140:Polyurethanes / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature; D013818:Thermogravimetry; D001559:Benzhydryl Compounds
chemical_list: D002368:Castor Oil; D017953:Isocyanates; D011140:Polyurethanes; C028279:polyurethane foam; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds
keywords: Castor oil polyol; Mechanical properties; Nanocrystalline cellulose; Polyurethane foams; Thermal properties