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

    15 Citations (Scopus)


    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
    JournalACS Sustainable Chemistry & Engineering
    Issue number11
    Publication statusPublished - 5 Nov 2018
    MoE publication typeNot Eligible


    We acknowledge funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 788489). We also acknowledge funding support by the European Regional Development Fund (Foam Forming Program 2015−2017) and the Academy of Finland under the Project SIRAF. We appreciate the provision of facilities and technical support by Aalto University at OtaNano-Nanomicroscopy Center (Aalto-NMC).


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


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