Foam Processing of Fibers As a Sustainable Alternative to Wet-Laying: Fiber Web Properties and Cause-Effect Relations

Wenchao Xiang, Ilari Filpponen, Erkki Saharinen, Timo Lappalainen, Kristian Salminen, Orlando J. Rojas (Corresponding Author)

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

Wet-laying is a mature technology that is applied in large scale for the manufacture of nonwovens, including paper products. However, it usually uses large volumes of water and is energy-intensive. Here we used foam-laying to substantially diminish the volume of water consumed in the formation of fiber networks (5-fold reduction) and to reduce the water content of the nonwovens produced before drying, achieving a reduced energy demand. The prospects of foam-laying were evaluated by comparing foam-laid and wet-laid webs of two types of wood fibers: stiff (lignin-containing) or flexible (lignin-free). Also, the effect of foaming agent type (anionic, cationic, nonionic, and amphoteric) was elucidated. Reference webs were produced by conventional wet-laying, with or without surfactants. Foam-laying was effective in producing a more uniform areal mass distribution (better formation) after wet-pressing. This effect was more evident for the webs synthesized with the flexible fibers. Unlike the layered network structures that were obtained by wet-laying, foam-laid webs exhibited a more felted network, with fibers positioned in the out-of-plane direction. As a result, higher air permeability, web porosity, and light scattering coefficients were measured for the foam-laid webs. The enhanced porosity (lower density) was related to the effect of bubbles during foam-laying and the reduction in surface tension of the foamed-fiber dispersion. The resistance to delamination of low-density webs obtained by foam-laying in the out-of-plane direction was preserved. However, the reduction in tensile strength and modulus of foam-laid webs were determined, owing to the reduced density of the formed structures. Notably, the type of foaming agent used played a minor role as far as the resultant properties of the webs, making the process flexible in terms of the selection of environmentally friendly alternatives. Overall, we compared the physico-mechanical properties of fiber networks formed by web- and foam-laying, depending on fiber type and foaming agent, yielding a property space that is useful in the design of lightweight structures (nonwovens, including paper). The prospects of water and energy savings by foam-laying are the major benefits in the sustainable use of fibers for the assembly of porous materials, such as lightweight nonwoven and paper products.

Original languageEnglish
Pages (from-to)14423-14431
Number of pages9
JournalACS Sustainable Chemistry & Engineering
Volume6
Issue number11
DOIs
Publication statusPublished - 5 Nov 2018
MoE publication typeNot Eligible

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Keywords

  • Felted structure
  • Foam-laying
  • Formation
  • Lignocellulosic fibers
  • Out-of-plane strength
  • Surfactants

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