Sunflower stalk neutral sulfite semi-chemical pulp: an alternative fiber source for production of fluting paper

• Neutral sulfite semi-chemical pulp was prepared from sunflower stalk.
• The pulp had very good response to refining, produced denser sheets.
• Produced papers revealed desired tensile-loaded and compression-loaded strengths.
• Fluting paper with better quality was made from the stalks than local hardwoods.

Sunflower stalk was evaluated as a potential fiber source to make fluting paper using neutral sulfite semi-chemical pulping process, in comparison with Mazandaran wood and paper industry mill made hardwood-based neutral sulfite semi-chemical (NSSC) pulp. Sunflower stalk consists of two distinct fractions including inner bulky pith and outer woody wall. The stalk has to be de-pithed for the purpose of papermaking because of lower cellulose, and higher ash content in pith-containing stalk. The results of pulping showed that the rate of delignification in NSSC cooking of de-pithed sunflower stalk with 20% lignin was surprisingly very low, despite of being a non-wood fiber source. However, sunflower stalk NSSC pulp showed very good response to refining and produced denser sheet due to lower digester yield and higher fiber flexibility coefficient, in comparison with Mazandaran wood and paper industry pulp sample. In addition, sunflower stalk pulp has been demonstrated to be an appropriate fiber source for making fluting paper at higher or comparable tensile-loaded strength properties such as tensile and burst, and higher compression-loaded strength properties including corrugated medium test and ring crush test.