Mechanical Properties Of Paper Research Articles

An elliptical pore model for the mechanical properties of paper

A simple mechanical model for paper comprising only isotropic cell-wall cellulose and a single elliptical pore is presented. Finite element method analysis applied to this model produced two stress-strain curves equivalent to the anisotropy observed in machine-made paper. Nissan’s hydrogen-bond domination theory for cellwall material with a density of 1000 kg/m3 provided the stress-strain functionality to control the displacement of the mesh nodes. Experimental data were collected from a single roll of paper produced on a pilot machine run where formation was decreased in five steps. Fiber properties, sheet grammage, and density were held constant in the final paper. Regardless of the level of formation, all breaking stress and strain data fell into one of two stress-strain curves, a machine-direction curve and a cross-direction curve. The initial modulus of each stress-strain curve was used to estimate the shape of the elliptical pore used in the finite element method model. The results for the model matched the results from the experimental data.

An evaluation of changes induced by wet cleaning treatments in the mechanical properties of paper artworks

Wet cleaning of ancient papers is a common treatment performed for the removal of degradation products, external contaminants and salts, which can promote the degradation of cellulose (i.e., hydrolysis, oxidation). In this research, the effects on the mechanical properties of paper samples caused by wet cleaning treatments were evaluated by considering the changes induced in the ultimate tensile strength, deformation at break and flexibility. For this purpose, samples were subjected to different aqueous cleaning treatments such as immersion in deionised water and the application of rigid gels of agar and gellan gum at different concentrations was carried out. Tensile tests were run, and morphological observations of paper by means of light microscopy and scanning electron microscopy were recorded. Contrary to the significant changes in the mechanical properties of paper samples after immersion treatment (an increase in flexibility as the elongation at break), the use of gelled systems caused slight improvement in the mechanical properties of paper (in both the ultimate tensile strength as well as in the breaking strain). Changes in the mechanical properties of paper were also correlated with slight changes in the diameter of the cellulose fibres as a consequence of the swelling action of water molecules, especially in the case of immersion treatment. Finally, the tensile tests performed on the paper samples after thermo-hygrometric accelerated artificial ageing (70 °C and 65 % RH) demonstrated that cleaning treatments by rigid gels did not seem to accelerate any sort of paper degradation in the mid to long term.

Enzymatic Refining and Cellulose Nanofiber Addition in Papermaking Processes from Recycled and Deinked Slurries

Recycling and deinking processes cause fiber damage because of hornification phenomena and increased external fibrillation. Mechanical refining has been used for many years to enhance the mechanical properties of paper. Biorefining of pulp using enzymes is receiving increasing interest for energy reduction at the refining step of the paper-making process. Moreover, enzymes have also been used for the enhancement of mechanical properties without affecting the drainage rate. As an alternative to mechanical refining treatment, a combination of an enzymatic treatment and cellulose nanofibril (CNF) addition was explored to enhance the mechanical properties of paper. The tests were carried out on a deinked pulp (DIP) suspension made of 50% old newspapers (ONP) and 50% old magazines (OMG). Various enzyme charges and CNF amounts were added to the mixture of ONP and OMG. All pulps (treated and untreated) were characterized from a morphological point of view, and the paper sheets made thereof were mechanically characterized. The combination of the enzymatic treatment with the addition of 3% CNF provided sufficient tensile strength for the paper to be used in high-performance applications

3D analysis of paper microstructures at the scale of fibres and bonds

The evolution of paper microstructure parameters, such as porosity and fibre orientation, as a function of papermaking conditions is most often studied at a macroscopic scale. However, modelling the physical and mechanical properties of papers using upscaling approaches requires understanding the deformation micro-mechanisms that are induced by papermaking operations within the structure of paper fibrous networks for individual fibres and fibre-to-fibre bonds. We addressed this issue by analysing three-dimensional images of model papers. These images were obtained using X-ray microtomography. The model papers were fabricated by varying forming, pressing, and drying conditions. For each image, this analysis enabled an unprecedented large set of geometrical parameters to be measured for individual fibres (centreline, shape and inclination of the fibre cross sections) and fibre-to-fibre bonds (inter-bond distance, number of bonds per unit length of fibre, bond surface area) within the fibrous networks. The evolution of the as-obtained microstructure parameters was analysed as a function of papermaking conditions. All results were in accordance with the data available in the literature. A key result was obtained for the evolution of the number of fibre-to-fibre contacts per fibre as a function of the network density. A representative number of contacts was obtained using relatively small imaged volumes. These volumes must only contain enough fibre segments the cumulated length of which is of the same order as the mean fibre length. These results were also used to validate microstructure models for the prediction of the number of fibre-to-fibre contacts within fibrous networks.

Improvement of the mechanical properties of paper by starch coatings modified with sepiolite nanoparticles

The modern and rapidly developing paper and board industry requires more efficient agents for the surface of paper in order to improve the mechanical properties. The starch coating used for the reinforcement of schrenz (110 g/m2) contained ultrasonicated nanoparticles of the mineral sepiolite. The viscosity of starch dispersions modified with different concentration of sepiolite was followed at the temperature of the coating on schrenz. The values of the breaking length, bursting strength and CMT‐strength of the paper reinforced with modified starch were increased by up to 20%. The viscoelastic properties as storage modulus were increased, too. Scanning electron microscopy of the samples showed deagglomeration and homogeneity of the sepiolite nanoparticles.

Merging Interstage Fractionation and Low Consistency Advantages During the TMP Refining Process: Part III – How Fibre Morphology Impacts Paper Properties

Fibre morphology and its evolution during refining and fractionation at low consistency were studied to understand the key relationships between the mechanical properties of paper and those of fibres. A broad analysis is presented on the physical and mechanical properties characterising the intrinsic morphological properties of fibres. The experimental refining process involved a primary stage at high consistency (HC), a fractionation stage with a small aperture basket, a low consistency (LC) refining stage, and a final high consistency refining (HCR) stage. The idea was to benefit from the pulp already being at low consistency following the screening step. Using a higher proportion of low consistency refining (LCR) tended to lower the tensile strength at 100 mL CSF, but some intermediate values did exhibit better responses to refining. Fractionation permits the use of LCR to retain fibre length and to develop additional long fibre bonding. The net gain remains even with energy reduction. It is believed, among other things, that a greater number or greater intensity of fibre-to-bar contacts would help increase internal delamination of the fibre structure.

Near infrared assessment of biodegradability and mechanical properties of paper made of cellulose sulfate bleached coniferous pulp with addition of cationic starch and resinous adhesive

The goal of this work was to develop Fourier-transform-near-infrared-spectroscopy-based methodology for monitoring kinetics and estimating the biodegradation rate of coniferous pulp paper. Two experiments with paper-degrading fungi were tested: one with Chaetomium globosum alone and the other with a mixture of Aspergillus niger, Trichoderma viride, and Penicillium funiculosum. Paper sheets made of fibers with the addition of 0, 2, 3, or 5% of cationic starch and resinous adhesive were used as test samples. In order to quantify the resistance of the paper to biodegradation, tests of breaking length and evaluation of the degree of fungal infestation were performed during infestation. It was found that addition of cationic starch and resin adhesives improved mechanical properties of paper; however, it also increased susceptibility to fungal colonization. Degradation of paper colonized by C. globosum was more advanced and exhibited more rapid kinetics. Spectral analysis revealed that spectra were most varying in bands 4283, 4400, 4742, and 4808 cm−1, which correspond to –CH, and –OH functional groups of cellulose and hemicelluloses. Differences in spectra were in good agreement with the reference methods; therefore this technique has potential for monitoring the paper biodegradation process and predicting changes in the paper's mechanical properties.

The effect of using willow wood on the optical and mechanical properties of newsprint paper obtained from chemi-mechanical pulp

In this study, the effect of mixing willow wood species with other wood species used in Mazandaran wood and paper industry on the optical and mechanical properties of newsprint paper made from chemi-mechanical pulp (CMP) was investigated. CMP pulp was made under condition of efficiency of 85 %, cooking time of 60 min, temperature of 170° C, and L:W = 7, sulfite percentage of 20 % based on the dry weight of the willow wood species in 6 levels. After handmade papers (60 g/cm2, gsm) were prepared, optical and mechanical properties of papers were evaluated. Results showed that the best optical properties were related to papers obtained from the factory pulps (control pulp), and only the opacity of papers obtained from willow paper pulp mixed with factory pulps has been in acceptable level (45:55, 45 % willow pulp to 55 % of the factory pulp). The best strength properties were observed in the incorporation of 100 % factory CMP pulp and in second priority 60:40 mixture (include 60 % of willow pulp with 40 % of factory CMP pulp). Due to the importance of strength properties compared to the optical properties in newsprint paper, incorporation of 60 % of willow pulp with 40 % of factory CMP pulp is suggested for newsprint paper.

Boosting the extensibility potential of fibre networks: A review

Production of paper-based packaging is growing at the present moment and has great future prospects. However, the development of new packaging concepts is creating a demand for an improvement in the mechanical properties of paper. Extensibility is one of these properties. Highly extensible papers have the potential to replace certain kinds of plastics used in packaging. Extensibility is also important for the sack and bag paper grades and for runnability in any converting process. This paper reviews the factors that affect the extensibility of fibres and paper, and discusses opportunities for improving the straining potential of paper and paper-like fibre networks. It is possible to classify factors that affect extensibility into three main categories: fibre structure, interfibre bonding, and structure of the fibre network. Extensibility is also affected by the straining situation and the phase state of the polymers in the cell wall. By understanding the basic phenomena related to the elongation, and by combining different methods affecting the deformability of fibre network, extensibility of paper can be raised to a higher level.

Boosting the extensibility potential of fibre networks: A review

Production of paper-based packaging is growing at the present moment and has great future prospects. However, the development of new packaging concepts is creating a demand for an improvement in the mechanical properties of paper. Extensibility is one of these properties. Highly extensible papers have the potential to replace certain kinds of plastics used in packaging. Extensibility is also important for the sack and bag paper grades and for runnability in any converting process. This paper reviews the factors that affect the extensibility of fibres and paper, and discusses opportunities for improving the straining potential of paper and paper-like fibre networks. It is possible to classify factors that affect extensibility into three main categories: fibre structure, interfibre bonding, and structure of the fibre network. Extensibility is also affected by the straining situation and the phase state of the polymers in the cell wall. By understanding the basic phenomena related to the elongation, and by combining different methods affecting the deformability of fibre network, extensibility of paper can be raised to a higher level.

Effects of Complex Flame Retardant on the Thermal Decomposition of Natural Fiber

Natural fiber is a renewable resource characterized by its low cost and environmental friendliness. However, flame retardant properties are one of the biggest limitations for the preparation of composite materials that need to be improved. In this work, a novel complex flame retardant consisting of aluminum hydroxide (ALH) and decabromine diphenyl oxide (PBDE) was proposed to inhibit the thermal decomposition. Flame-retarding paper was made from softwood pulp and complex flame retardant. The thermal properties of the flame retardants were studied using thermogravimetric analysis (TGA). The mechanical properties of paper treated at different temperatures were tested, while the surface characteristics of natural fiber were detected by a scanning electron microscope (SEM) and atomic force microscope (AFM); their specific surface areas were also measured. The optimum value of aluminum hydroxide to decabromine diphenyl oxide was 3 to 1, added at 70% based on dried natural fiber. It also had good flame retardant performance and mechanical properties at 200 °C for 5 min; meanwhile, the tensile index of the handsheet was 82.5 Nm/g, and the specific surface area was 0.414 m2/g.

From paper to nanopaper: evolution of mechanical and physical properties

In the present work the evolution of physical and mechanical properties of papers and nanopapers is studied. Handsheets made of eucalyptus fibres reinforced with 0, 25, 50, 75 and 100 wt% of nanofibrillated cellulose (NFC) content were fabricated using a Rapid Kothen-like equipment. The obtained papers and nanopapers were physical- and mechanically-characterized. The results showed a significant increase in density and a reduction of porosity in the samples during their transition from paper to nanopaper; besides, nanopapers were more transparent and smoother than normal papers. These physical changes where more evident with increasing amounts of NFC. Regarding mechanical properties, nanopapers with a 100 wt% content of NFC improved their strength and rigidity in 228 and 317 %, respectively, in comparison with normal papers. The evolution of strength and rigidity from paper to nanopaper was linear in relation to the amount of NFC, which means that the ultimate tensile strength was mainly dependant on nanofibril failure.

Changes of Handsheet Fracture Toughness by Wood and Cotton Fibers Mixing

Conditions of paper manufacturing process should be changed depending on the end use and paper properties. Most of the case, mixed pulps with long softwood fibers and short hardwood fibers are used to achieve proper qualities of product with reasonable production cost. For specialty paper manufacture the wood pulp and cotton linter pulp are usually mixed together. The objectives of this study is to analyze physical, mechanical and fracture mechanical properties of paper depending on SwBKP, HwBKP and cotton linter pulp(CLP) mixing. When the mixing ratio of SwBKP was increased, strength properties, such as tensile, tear, and folding endurance, were also increased. When the mixing ratio of SwBKP and HwBKP was increased, stress concentration index was decreased and fracture toughness was increased.

Improvement of Paper Properties of Rice Straw Pulps by Microcrystalline Cellulose/Calcium Carbonate

Rice straw is a locally available lignocellulosic material. In this study rice straw was pretreated by soaking it in water for 48 hours at room temperature. The pretreated straw was cooked in 5% NaOH at 100∫C and atmospheric pressure.The structure and mechanical properties of paper made from cooked pulp was investigated. Hydrogen peroxide as a bleaching agent was applied to the pulp to enhance its brightness level in a single stage process in the presence of sodium hydroxide and magnesium sulfate. Rice straw pulp, bleached using 2% hydrogen peroxide solution, was selected to prepare microcrystalline cellulose (MCC). The MCC was characterized by 45.5% crystallinity and nano in size vide XRD and TEM respectively. Microcrystalline cellulose and calcium carbonate were added to unbleached pulp as fillers. Air permeability of filled paper was improved in the presence of MCC more than in the presence of calcium carbonate alone. Optical properties and water permeabil ity of filled pulp showed improvements in the presence of microcrystalline cellulose filler compared to unfilled pulp.

MECHANICAL PROPERTIES OF FLEXOGRAPHIC PRINTS / FLEKSOGRAFINIŲ ATSPAUDŲ MECHANINĖS SAVYBĖS

Mechanical properties of paper and flexographic prints madewith different anilox rollers were investigated experimentally.Flexographic prints roughness, breaking force and folding resistancevalues were determined. The results showed that foldingresistance is bigger for machine direction prints than for crossmachine direction prints. Flexographic prints on cardboardsfolding resistance values are different for machine direction andcross machine direction. It was determined that roughness offlexographic prints increases with the amount of ink on aniloxroller. Results were explained by the ink water influence. Santrauka Eksperimentiškai ištirtos įvairių rūšių popieriaus ir fleksografinių atspaudų, gautų dengiant popierių skirtingo plotinio tūrio aniloksiniais voleliais, mechaninės savybės. Nustatytos popieriaus ir fleksografinių atspaudų šiurkštumo, atsparumo tempimui bei atsparumo lenkimui vertės. Gauti rezultatai parodė, kad atspaudų atsparumas lankstymui yra didesnis išilgine nei skersine popieriaus kryptimi. Dengiant kartonus fleksografiniais dažais, atsparumas tempimui keičiasi, ir ši kaita yra skirtinga išilgine ir skersine kryptimis. Nustatyta, kad fleksografinio atspaudo šiurkštumas didėja, storėjant dažų sluoksniui ant aniloksinio volelio. Manoma, kad taip nutinka dėl dažuose esančio vandens.

Effects of cationic xylan from annual plants on the mechanical properties of paper

Xylan from oat spelt and wheat was used as an additive to enhance the dry strength of paper. The absorption of xylan by the cellulose fibers was increased by cationization to different degrees of substitution. Paper hand sheets with different doses of xylan and industrial cationic starch were produced, and the mechanical properties were determined. Absorption measurements of cationic oat spelt xylan on pulp fibers explained the differing influences of low and high cationized xylan addition on paper strength. The addition of cationic oat spelt xylan with a degree of substitution of 0.1 at a 4% dose provided the largest improvement in the tensile-index (67%), burst-index (105%) and tear-index (77%). Compared to cationic starch, cationic oat spelt xylan additives led to similar paper strength values, excepting the tear strength. The structural differences and protein impurities made the wheat xylan unsuitable as a strength additive for paper pulp.

3D Forming of Paperboard: The Influence of Paperboard Properties on Formability

Paper and paperboard are widely used in various types of packaging. Paper-based packaging is a recyclable, biodegradable, renewable and sustainable product, which gives it certain advantages over most plastic-based packaging materials. Although paper-based packaging, in some areas, lacks attractiveness in terms of visual appearance, 3D forming is an important method for producing advanced shapes from paper and paperboard, suitable, for instance, for modified atmosphere packaging. That said, very little is known about the deformations experienced by paper-based materials in 3D forming. Understanding the role played by the mechanical properties of paper and paperboard in the 3D forming process is key to improving performance. This paper presents experimental results obtained using three different forming devices designed to be used with paper-based materials and links the formability data with specific mechanical properties of the paperboard samples. Paperboard properties that were found to correlate with formability were as follows: compressive strength and strain, tensile strain, paper-to-metal friction and out-of-plane stiffness. The requirements for formability are different for the fixed blank forming process and sliding blank forming process. Copyright © 2013 John Wiley & Sons, Ltd.

Deacidification of Paper Using Supercritical Carbon Dioxide Containing Calcium Propionate or Magnesium Bicarbonate

Supercritical carbon dioxide (SCCO2) containing calcium propionate or magnesium bicarbonate was used to deacidify paper. In the experiment, to compare the effects of SCCO2 technology deacidification and immersion deacidification, two kinds of paper samples were chosen to do these two kinds of deaciditication tests respectively. And pH, alkali reserve and mechanical properties of paper samples were measured before and after these treatments. The experiments showed that the pH and alkaline reserve of paper samples treated with SCCO2 were nearly similar to that of immersion treatments. Otherwise, compared with immersion deacidification, supercritical carbon dioxide had some advantages of strengthening the mechanical properties of paper and shortening treatment time.

Empirical plasticity models applied for paper sheets having different anisotropy and dry solids content levels

The rheological nature of paper or board is usually treated either as elasto-plastic or as viscoelastic depending on the studied paper making process or behavior in converting and end use. In this paper we study several stress–strain curve models and the determination of material parameters from an elasto-plastic point of view. Finally, a suitable approach for all stress–strain curves measured from 180 strips is constructed using a linear function for an elastic region and a nonlinear function for a strain hardening region. This model determines a proportional limit (elastic limit) and gives fairly elegant dependencies between material/fitting parameters and two important factors of mechanical properties of paper: dry solids content and anisotropy. In this paper the dependency of a plastic strain on dry solids content and anisotropy is estimated using the introduced stress–strain curve model. Correspondingly, the model can be used to estimate many other mechanical behaviors, for example, the tension differences arising from non-uniform moisture content of the paper web profile. However, the main target of this study is to produce competent parameters based on modeled stress–strain curves for further construction of a material model. This elasto-plastic material model will be utilized in out-of-plane deformation and fracture models.

Influence of Liquid or Solid Phase Preparation of Cationic Hemicelluloses on Physical Properties of Paper

Cationizations of galactomannan- and xylan-type hemicelluloses were performed in a solid state, with 2,3-epoxypropyltrimethylammonium chloride (ETA) as the cationic reagent under alkaline conditions. By this method, the reaction efficiency was significantly increased for all hemicellulose types, up to 90% in the case of xylan. The consumption of reagents was reduced by a factor of ten when compared to the reaction in liquid phase, while comparable values of the degree of substitution (DS) were obtained. By reducing the number of purification steps, the consumption of solvents was limited, and high mass yields were preserved. By all aspects, this method constitutes an economical and environmental gain for the cationization reaction of hemicelluloses. Native hemicelluloses and their cationic derivatives were tested as additives to the pulp slurry in order to increase the dry strength of the paper formed. The cationization of hemicelluloses had a beneficial effect on the mechanical properties of paper, with a supplementary gain of properties compared to the unmodified polysaccharides. Cationic derivatives of a DS 0.3 gave the best results for both polysaccharides, with the galactomannan-type being more efficient than the xylan-type with a 90% increase of the burst index.