Impact of degree of substitution of cationic xylan on strength of cellulose fiber networks along with medium conductivity

Hemicelluloses have been considered as an efficient component to improve the bonding or strength of fiber networks. The degree of substitution (DS) of cationic hemicelluloses and the ionic strength of applied medium are therefore two most important and crucial factors influencing its performance in wet-end of papermaking. Therein, the impact of DS of cationic xylan (CX) derived from corncob on the strength of fiber networks was systematically explored in aqueous media with various ionic strengths. Initially, a series of CXs with DS ranging from 0.051 to 0.113 were synthesized via a microwave-assisted method. The resulting CXs were applied as wet end additives in the media with conductivity of 500, 2500, and 5000 mu s/cm, representing the low, moderate, and high level of electrolytes in closed white water circulation, respectively. Comparing to the control, all CXs improved the tensile and tear strength of paper significantly, while not in burst strength. The medium conductivity had an adverse impact on the performance of CXs, and the optimum DS of CXs was down shifted to about 0.05 +/- 0.06. To mimic the adsorption of CXs on fiber surface, the adsorption behavior of CXs on negatively charged gold sensor was monitored by SPR in an attempt to reveal the mechanism. It was found that CXs with low DS had a larger adsorption capacity, thicker and softer adlayer, which are beneficial to fiber bonding and paper strength. This study is meaningful to the applications of xylan into value-added products and to the valorization of agricultural and forestry wastes.

Automated summary

The study indicates that the degree of substitution of cationic hemicelluloses significantly affects their performance in the wet end of papermaking, with the optimum DS varying under different ionic strengths. Cationic xylan with low DS shows better enhancement on fiber network bonding and paper strength.