On the strength improvement of lightweight fibre networks by polymers, fibrils and fines

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ORIGINAL RESEARCH

On the strength improvement of lightweight fibre networks by polymers, fibrils and fines Tiina Po¨hler . Jukka A. Ketoja . Timo Lappalainen . Veli-Matti Luukkainen . Ilkka Nurminen . Panu Lahtinen . Katariina Torvinen

Received: 28 June 2019 / Accepted: 21 May 2020 Ó The Author(s) 2020

Abstract Novel lightweight cellulose fibre materials containing various strength enhancing polymeric and fibrillar components were formed with the help of foam technology. Increasing inter-fibre bond strength and local material density was attempted with unique lignin-containing wood fines (V-fines), cellulose microfibrils (CMF), TEMPO-oxidized cellulose nanofibrils (TCNF), and macromolecules such as cationic starch, polyvinyl alcohol (PVA), and locust bean gum (LBG). The investigated fibres included both long hemp bast fibres and northern bleached softwood Kraft pulp. In the low-density range of 38–52 kg/m3, the compression stress and modulus were highly sensitive to inter-fibre bond properties, the multi-scale features of the fibre network, and the foaming agent employed. Still, the compression-stress

behaviour in most cases approached the same theoretical curve, derived earlier by using a mean-field theory to describe the deformation behaviour. At 10% addition level of fine components, the specific compression stress and compression modulus increased in the order of V-fines \ CMF \ TCNF. A tremendous increase in the compression modulus was obtained with LBG, leading to a material surface that was very hard. In general, the foams made with PVA, which acts both as foaming agent and reinforcing macromolecule, led to better strength than what was obtained with a typical anionic sodium dodecyl sulphate surfactant. Strength could be also improved by refining the softwood pulp.

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03263-x) contains supplementary material, which is available to authorized users. T. Po¨hler (&)  J. A. Ketoja  T. Lappalainen  V.-M. Luukkainen  I. Nurminen  P. Lahtinen  K. Torvinen Solutions for Natural Resources and Environment, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, 02044 Espoo, Finland e-mail: [email protected]

123

Cellulose

Graphic abstract

Keywords Foam forming  Cellulose nanofibril  Wood fines  Fibre  Softwood  Hemp  Polyvinyl alcohol  Locust bean gum  Compression test  Stress  Strain  Model

Introduction New low-density cellulose-based fibre materials made with the foam forming technique have recently been introduced as potential solutions to replace oil-based fibrous or foamed materials (Poranen et al. 2013; Madani et al. 2014). Feasible applications can be found in air filtration (Jahangiri et al. 2014), thermal insulation (Jahangiri et al. 2014; Po¨hler et al. 2017), in acoustic control as sound absorption material (Jahangiri et al. 2016; Po¨hler et al. 2016), and as cushioning material in packaging (Luo et al. 2017; Paunonen et al. 20