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

TY - JOUR

T1 - Foam Processing of Fibers As a Sustainable Alternative to Wet-Laying

T2 - Fiber Web Properties and Cause-Effect Relations

AU - Xiang, Wenchao

AU - Filpponen, Ilari

AU - Saharinen, Erkki

AU - Lappalainen, Timo

AU - Salminen, Kristian

AU - Rojas, Orlando J.

PY - 2018/11/5

Y1 - 2018/11/5

N2 - 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.

AB - 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.

KW - Felted structure

KW - Foam-laying

KW - Formation

KW - Lignocellulosic fibers

KW - Out-of-plane strength

KW - Surfactants

UR - http://www.scopus.com/inward/record.url?scp=85054698495&partnerID=8YFLogxK

U2 - 10.1021/acssuschemeng.8b03102

DO - 10.1021/acssuschemeng.8b03102

M3 - Article

AN - SCOPUS:85054698495

VL - 6

SP - 14423

EP - 14431

JO - ACS Sustainable Chemistry & Engineering

JF - ACS Sustainable Chemistry & Engineering

SN - 2168-0485

IS - 11

ER -