Influence of addition of fine cellulose fibers on physical properties and structure of paper

Abstract

Recently, various fine cellulose fibers (CFs) such as cellulose nanofiber and microfibrillated cellulose have been developed. However, it is not clear how the addition of these fine CFs influences the physical properties and structure of paper. This study examines the benefits of adding fine CFs, including nano- and submicron-sized CFs, to paper by mixing them into unbeaten pulp, and discusses CF size differences between the micron and smaller scales. Two types of CFs were used in this study. One consists of micro-, submicron-, and nano-sized CFs (CF1) and another consists of nano- and submicron-sized CFs (CF2). The results show that both CF1 and CF2 enhance the tensile index, stretch at break, and tensile energy absorption of a handsheet. To explain these results, the fiber strength index and bond strength index were calculated using the Page's equation, and the tensile index for the handsheets with CF1 and CF2 showed a strong correlation with the bond strength index, thus suggesting that CF1 and CF2 were deposited in locations where there was interfiber bonding. However, differences were observed in the internal structures of the paper samples, indicating that CF2 did not change the pore volume and pore size of the resulting samples.