Residual lignin inhibits thermal degradation of cellulosic fiber sheets

Research output: Contribution to journalArticleScientificpeer-review

Researchers

Research units

  • VTT Technical Research Centre of Finland

Abstract

The market for cellulosic fiber based food packaging applications is growing together with the importance of improving the thermal durability of these fibers. To shed light on this, we investigated the role of residual lignin in pulp on the thermal stability of refined pulp sheets. The unbleached, oxygen delignified, and fully bleached pulp sheets were studied after four separate refining degrees. Comparison by Gurley air resistance, Bendtsen porosity, and the oxygen transmission rate tests showed that lignin containing sheets had better air and oxygen barrier properties than fully bleached sheets. Sheet density and light scattering coefficient measurements further confirmed that the lignin containing pulps underwent more intense fibrillation upon refining that changed the barrier properties of the sheets. Thermal treatments (at 225 °C, 20 and 60 min, in water vapor atmospheres of 1 and 75 v/v %) were applied to determine the thermal durability of the sheets. The results revealed that the residual lignin in pulps improved the thermal stability of the pulp sheets in the hot humid conditions. This effect was systematically studied by tensile strength, brightness, and light absorption coefficient measurements. The intrinsic viscosity results support the findings and suggest that lignin is able to hinder the thermal degradation of pulp polysaccharides. In spite of the fact that lignin is known to enhance the thermal yellowing of paper, no significant discoloration of the pulp sheets containing residual lignin was observed in the hot humid conditions (75 v/v %). Our results support the idea of lignin strengthening the thermal durability of paper.

Details

Original languageEnglish
Pages (from-to)199-212
Number of pages14
JournalCellulose
Volume23
Issue number1
Publication statusPublished - 1 Feb 2016
MoE publication typeA1 Journal article-refereed

    Research areas

  • Antioxidant properties, Refining, Residual lignin, Strength loss, Thermal degradation, Thermal yellowing

ID: 1508091