title: Tunable softening and toughening of individualized cellulose nanofibers-polyurethane urea elastomer composites.
abstract: A series of elastomeric nanocomposites with superior tensile strength and extensibility, simultaneously exhibiting softening, was prepared using in situ polymerization by homogeneously dispersing TEMPO-oxidized cellulose individualized nanofibers (TOCNs) in a polyurethane urea (PUU) matrix. The structure of these PUU composites covalently cross-linked with the TOCNs was characterized. It was interesting to find that the amount and size of the hard domains in the composites gradually decreased by introducing crosslinkable TOCNs. With only 2wt% of TOCNs incorporated, a 10.4-fold increase in tensile strength, 5.5-fold increase in strain-to-failure, and a decrease of 35% in the coefficient of thermal expansion were achieved, compared with those of neat PUU. However, the elastic modulus of the nanocomposites gradually decreased with up to 1wt% of TOCNs. Conversely, with 2wt% of TOCNs, the stiffness of the elastomers again increased, due to filler-filler interaction over the CNFs percolation in the nanocomposites.
authors.affiliation: Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Republic of Korea.
authors.forename: Minwoo
authors.initials: M
authors.lastname: Lee
authors.affiliation: Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Republic of Korea; Department of Green Chemistry and Environmental Biotechnology, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea.
authors.forename: Min Haeng
authors.initials: MH
authors.lastname: Heo
authors.affiliation: Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Republic of Korea; Department of Green Chemistry and Environmental Biotechnology, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea.
authors.forename: Hwi-Hui
authors.initials: HH
authors.lastname: Lee
authors.affiliation: Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Republic of Korea; Department of Green Chemistry and Environmental Biotechnology, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea. Electronic address: ywkim@krict.re.kr.
authors.forename: Young-Wun
authors.initials: YW
authors.lastname: Kim
authors.affiliation: Center for Biobased Chemistry, Korea Research Institute of Chemical Technology, 141 Gajeong-ro, Yuseong-gu, Daejeon, 34114, Republic of Korea; Department of Green Chemistry and Environmental Biotechnology, University of Science & Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon, 34113, Republic of Korea. Electronic address: jshin@krict.re.kr.
authors.forename: Jihoon
authors.initials: J
authors.lastname: Shin
keywords: Cellulose nanofibers; Chemical cross-linking; Ductile; Nanocomposites; Toughening