Carboxymethylcellulose (CMC) as a model compound of cellulose fibers and polyamideamine epichlorohydrin (PAE)-CMC interactions as a model of PAE-fibers interactions of PAE-based wet strength papers

Carboxymethylcellulose (CMC) is a cellulose derivative obtained by the carboxymethylation of some hydroxyl groups in the cellulose macromolecules. In this article, we use CMC as a model compound of cellulose fibers to study polyamineamide epichlorohydrin (PAE)-fibers interactions during the preparation of PAE-based wet strength papers. The main advantages of the use of CMC to replace cellulose fibers are its water-soluble character and the homogeneous reaction medium during mixing with PAE resin. Based on C-13 cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) and Fourier transformed infra-red (FTIR) spectroscopy, we prove the formation of ester bonds in PAE-CMC films boosted by a thermal posttreatment at 105 degrees C for 24 h. These ester bonds are derived from a thermally induced reaction between carboxyl groups in the CMC structure and azetidinium ions (AZR) in the PAE resin. PAE-based handsheets were prepared from 100% Eucalyptus fibers. After preparation, some samples were thermally posttreated (TP) at 130 degrees C for 10 min and stored under controlled conditions (25 degrees C and 50% relative humidity or RH). For lowest PAE dosage, storage of the not thermally posttreated (NTP) PAE-based handsheets does not allow them to reach the tensile strength values of TP PAE-based handsheets (at 130 degrees C for 10 min), but the difference in terms of breaking length remains low. For the highest PAE addition level, NTP and TP PAE-based handsheets exhibit close values of the breaking length from 30 days of storage under controlled conditions (25 degrees C and 50% RH). When a thermal posttreatment is applied, the wet strength development of PAE-based papers is a combined effect of homo- and co-cross-linking mechanisms. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42144.