Ammonia Emissions in the 1980s

Niskanen, R.; Keranen, S.; Pipatti, Riitta

doi:10.1007/978-3-642-75450-0_3

Cited by 6 publications

(8 citation statements)

References 9 publications

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“…For a given fiber type, differences in web strength originate from structural features, which may cause the difference in the interfiber bonding patterns and load carrying points of foam- and wet-laid webs. The typical evaluation of web strength with tensile strength is based on the assumption that fibers alone are responsible for the stretching failure . Therefore, the tensile index generally depends on the apparent density, which is shown in Figure a.…”

Section: Resultsmentioning

confidence: 99%

“…Empirically, the elongation at break of the fiber network relates to a universal failure threshold of fibers and/or bonds . For a given grammage, fiber type, and specimen dimensions, the presence of more out-of-plane fiber segments is expected to produce a weaker resistance to plastic deformation under tension, and, thus, display lower elongation at break (Figure b, right and blank panel).…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, photographic images of the fiber networks after foam-laying revealed that the hollow fiber structure was mostly preserved . This can possibly be explained by the weaker capillary forces that result from the lower surface tension (in the presence of surfactants) if one considers the Campbell effect , that brings fibers sufficiently close upon water removal to promote the formation of multiple interfiber hydrogen bonding.…”

Section: Introductionmentioning

confidence: 99%

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

Xiang

Filpponen

Saharinen

et al. 2018

ACS Sustainable Chem. Eng.

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Xiang

Filpponen

Saharinen

et al. 2018

ACS Sustainable Chem. Eng.

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“…As a result, Skowronski and Szwarcsztajn 36 concluded that paper would only react elastically below the Kubat stress. Similarly, Waterhouse 37 and Niskanen 38 stated that the Kubat stress must be overcome for any significant stress relaxation to occur. Niskanen 35 further discussed that stress relaxation may occur below the Kubat stress, but it is too slow to measure.…”

Section: Rheological Model Derivationmentioning

confidence: 97%

“…Given that stress relaxation and creep are effectively the inverse of one another, it is proposed that if such an activation stress exists for stress relaxation behavior, that it would also exist for creep behavior. Like Niskanen,38 it is not argued that time-dependent deformation ceases to occur below such an activation stress, but a change in deformation behavior occurs near this stress and all deformation below it can be ignored. As a result, an activation stress, r k , is incorporated in to eq.…”

Section: Rheological Model Derivationmentioning

confidence: 99%

Rheological modeling of the tensile creep behavior of paper

DeMaio

Patterson

2007

J of Applied Polymer Sci

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Paper is a networked structure of randomly bonded fibers. These fibers are composed of naturally occurring polymeric materials (cellulose, hemicelluloses, and lignin). Polymeric materials such as these exhibit viscoelastic deformation, and as a result, creep under an applied stress. A rheological model has been developed to predict the tensile creep behavior of paper under a uniaxial stress. Specifically, the focus of this model was to predict creep strain using only stress, time, and efficiency factor (effectiveness of bonding). This rheological model offers insight into creep behavior (drawing from molecular creep mechanisms) and separates total strain from creep into initial elastic, primary creep, and secondary creep components. Interfiber bonding is taken into account through the use of an efficiency factor which represents how effectively bonding is distributing load throughout the fiber network of the paper. As a result, this model makes it possible to predict the creep behavior of paper over a range of bonding levels, induced by mechanical changes in bonded area or chemical modification of specific bond strength, using creep data from paper at any single level of bonding. This utility is retained as long as the fibers and the orientation of the fibers are not changed.

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