Formation of polyelectrolyte multilayers on fibres: Influence on wettability and fibre/fibre interaction (original) (raw)
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Influence of electrostatic interactions on fibre/fibre joint and paper strength
Nordic Pulp & Paper Research Journal, 2004
A study was undertaken to explore the influence of electrostatic interactions between the fibres during sheet forming and sheet consolidation on the strength of both the fibre/fibre joints and the paper. To establish this relationship, the joint strength between individual fibres was determined and compared with the strength of sheets made from these corresponding fibres. Regenerated cellulose fibres with their charge varied by carboxymethylation (anionic fibres) and by treatment with glycidyltrimethylamoniumchloride (GTAC) (cationic fibres) were investigated. In addition to joint strength and sheet strength measurements, the fibre charge together with wet fibre flexibility and fibre swelling, were evaluated for the differently treated fibres. The joint strength between individual fibres decreased with increasing ionic strength whereas the sheet strength measurements showed an increase in strength with increasing ionic strength for the bulk charged fibres. These results were found for both anionic and cationic bulk charged fibres. The wet flexibility of the fibres increased with increasing bulk charge, but there was no change in flexibility with an increase in salt concentration. Furthermore, there was no change in flexibility by increasing the surface charge of the fibres. It is suggested that the increase in sheet strength with increasing charge of the fibre is due to increasing joint strength and that the decrease in joint strength with increasing salt concentration is due to a decrease in the surface swelling of the fibres and hence a less favourable interaction between the fibres. The increase in sheet strength for the bulk charged fibres with increasing salt concentration is probably caused by an increased probability for joint formation in the fibre/fibre contacts due to decreased electrostatic repulsion between the fibres. This is discussed in terms of a balance between electrostatic repulsion and attractive capillary forces between the fibres during forming and consolidation of the paper.
Industrial & Engineering Chemistry Research, 2006
Polyallylamine hydrochloride (PAH) and poly(acrylic acid) (PAA) were used to modify wood fibers by means of the polyelectrolyte multilayer (PEM) technique. Hand sheets and fiber crosses were prepared from the PEM-treated fibers. The sheet strength and fiber-fiber joint strength were evaluated, and the contact zone of the fiber-fiber joint was characterized using a recently developed staining technique. The nonjoined surface area of the paper sheets was estimated by determining nitrogen adsorption via BET analysis, and the results were compared with those of the light scattering measurements frequently used to determine the degree of "bonding" in paper. Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to analyze chemical effects. It was shown that the PEM treatment of fibers increased the strength properties of the sheets through an increase in the number of fiber-fiber joints, increasing the degree of contact in a fiber-fiber joint and creating covalent bonding in the fiber-fiber joint.
Fundamental aspects of adhesion between cellulosic surfaces in contact - a review
O Papel Revista Mensal De Tecnologia Em Celulose E Papel, 2011
This paper presents a review on the adhesion between cellulose fibers. The function of water in the assembly of paper is examined. The contributions of friction, interfibrilar water structure, hydrogen bonds, van der Waal forces, as well as electrostatic linkages therein are discussed. The phenomena of adhesion between wet cellulose fibers in the consolidation of a fibrous web can be visualized as a sequence of events with water playing a key role throughout. Initially, the drainage of water brings the fibers together to form the wet web where the water-structuring effects of the hydrophilic cellulose surfaces can contribute to long-range interactions to form a virtual gel between fibers. Subsequently, with the departure of more water, the cellulose surfaces are drawn even closer so that chemical interfiber bonds ranging from van der Waals forces through hydrogen bonds, ionic to covalent, if appropriate functional groups are present can become activated. Finally, the most common additives utilized commercially for the enhancement of interfiber adhesion are summarized in terms of the accepted operating mechanisms.
Adhesion between Cellulosic Fibers in Paper
Journal of Adhesion Science and Technology, 2011
The function of water in the adhesion between wet cellulose fibers both in the assembly of papers and the establishment of the properties is discussed. The contributions of friction and hydrogen bonds are reviewed, together with the new concept of interfiber ordered water structure created by the hydrophilic surfaces of the fibers. Procedures for the enhancement of interfiber adhesion are summarized in terms of the accessibility, the stereotopochemistry and the enthalpies of the interacting moieties on contiguous surfaces.
Polymers that strengthen never-dried joints between wet cellulose surfaces – A review
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Forming an adhesive joint between two wet cellulose surfaces before a drying step is important when manufacturing paper, foams, aerogels, other novel materials from wood pulp fibers, and various types of nanocellulose. This paper reviews the literature with an emphasis on the role of adhesive polymers on wet cellulose adhesion. Linkages between the organization of adhesives between the bonded surfaces and the strength of joints are emphasized. Relevant adhesion results from the surface forces apparatus, colloidal probe atomic force microscopy, paper wet-web strength, and wet-peeling of laminated regenerated cellulose membranes are considered.
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Langmuir, 2012
Adhesive force exists between polymer nano/microfibers. An elaborate experiment was performed to investigate the adhesion between polymer nano/ microfibers using a nanoforce tensile tester. Electrospun polycaprolactone (PCL) fibers with diameters ranging from 0.4−2.2 μm were studied. The response of surface property of electrospun fiber to the environmental conditions was tracked by FTIR and atomic force microscopy (AFM) measurements. The effect of temperature on molecular orientation was examined by wide angle X-ray diffraction (WAXD). The adhesive force was found to increase with temperature and pull-off speed but insensitive to the change of relative humidity, and the abrupt increase of adhesion energy with temperature accompanied by a reduced molecular orientation in the amorphous part of fiber was observed. Results show that adhesion is mainly driven by van der Waals interactions between interdiffusion chain segments across the interface.
Evaluating the degree of molecular contact between cellulose fiber surfaces using FRET microscopy
The degree of molecular contact, i.e. the contact area on the nanometer scale, between paper fibers is crucial for the van-der-Waals and hydrogen bond adhesion between the fibers and thus for the fiber-fiber bond strength. We apply Förster resonance energy transfer (FRET) to investigate the degree of contact in the distance range of 1-10 nm between pulp fiber bonds and between thin films. The FRET system with DCCH and FTSC as fluorescence dyes has been validated for spectrophotometry and for local imaging with widefield microscopy, using pHema thin films. Cellulose (2019) 26:7037-7050 https://doi.org/10.1007/s10570-019-02575-x( 0123456789().,-volV) ( 01234567 89().,-volV)
The area of molecular contact in fiber-fiber bonds
We are presenting a coherent theoretical concept as well as empirical evidence suggesting that there is a high degree of molecular contact in fiberfiber bonds, the surfaces might even be in full contact.
Journal of Colloid and Interface Science, 2005
Colloidal probe microscopy was employed to study forces between cellulose surfaces upon addition of a series of cationic copolymers in aqueous solution, as model compounds for wet strength agents. The content of quaternary ammonium groups and primary amines was systematically varied in the cationic polymers, to distinguish between the importance of electrostatical and H-bonding effects. Cellulose microspheres were glued at the apex of tipless microfabricated cantilevers and used as colloidal probes. Ultra thin cellulose films and cellulose fibres were employed as model surfaces. The cellulose films of a thickness of about 5 nm were spin-coated from cellulose solution onto silicon substrates. The root-mean-square-roughness (RMS) was 0.3-0.8 nm. The cationic model polymers were compared to Servamine, a polymer employed as standard wet strength resin in papermaking industries. Force versus separation measurements showed a detailed picture of adhesion and contact breaking. Relatively strong adhesion of the order of 0.3 mJ/m 2 was observed with Servamine within a range of approximately 10 nm. At larger distances weak bond breaking and elastic chain pulling were identified. When approaching the surface one to two small jump-in's possibly related to strong binding of Servamine and subsequent attraction could be found in the case of Servamine. In contrast, all the model copolymers showed only a weak adhesion of 8-30 µJ/m 2 , i.e., an order of magnitude less than that of Servamine and subsequent elastic rupture domains. The contour length, persistence length and characteristic rupture distances were calculated by means of applying the WLC model. Measurements against cellulose fibres obtained from the production process proved the relevance of the model systems. 2004 Elsevier Inc. All rights reserved.
What holds paper together: Nanometre scale exploration of bonding between paper fibres
Scientific Reports, 2013
Paper, a man-made material that has been used for hundreds of years, is a network of natural cellulosic fibres. To a large extent, it is the strength of bonding between these individual fibres that controls the strength of paper. Using atomic force microscopy, we explore here the mechanical properties of individual fibre-fibre bonds on the nanometre scale. A single fibre-fibre bond is loaded with a calibrated cantilever statically and dynamically until the bond breaks. Besides the calculation of the total energy input, time dependent processes such as creep and relaxation are studied. Through the nanometre scale investigation of the formerly bonded area, we show that fibrils or fibril bundles play a crucial role in fibre-fibre bonding because they act as bridging elements. With this knowledge, new fabrication routes can be deduced to increase the strength of an ancient product that is in fact an overlooked high-tech material.