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With the increasing popularity of coated paper, it has been more widely used in printing, publishing, product packaging and commercial promotion. However, coated paper is prone to cracks after printing and folding which exposes to a white area which is referred to as fold cracking. This study investigated the coating properties of paper and coating factors influencing the fold cracking and aimed to provide guidance on how to reduce the problems of fold cracking. This paper mainly discusses the effects of pigment proportion, binder dosage, solids content, coating thickness and calendering pressure on fold cracking of coated paper after printing. Experiments show that when the coating consisted entirely of calcium carbonate, the degree of fold cracking is most serious. With the addition of kaolin, the fold cracking reduces. When the ratio of the number of parts of calcium carbonate to kaolin is 25/75, the area of fold cracking reaches its minimum value of 10.28 %. With increasing solids content of the coating, the fold cracking decreases initially and then increases. When the solids content is 55 %, the fold cracking reaches a minimum. Increased latex content reduced coating thickness and an increase in calendering pressure gradually reduce the degree of fold cracking.

Crease cracking of paperboard is important to control for the appearance and structural integrity of packages. Crease cracking is affected by creasing operation variables, as well as the physical properties of the paperboard. However, the effects of the physical properties are not clearly known. The objectives of this work were to identify the key material properties that affect crease cracking and to clarify the effects of fiber composition and starch. Laboratory sheets were produced from bleached and refined softwood and hardwood commercial pulp at grammage and thicknesses that match a typical paperboard. To mimic papermaking operations, surface starch was applied via a bench-top size press. The sheets were creased in the lab over a range of penetration depths, and reverse-side cracking was measured. The results showed that less reverse-side cracking was correlated with higher tensile post-peak energy, a lower bending stress, and a lower z-direction (ZD) stiffness. The tensile post-peak energy is a measure of the resistance to crack growth via fiber-bridging. The bending force and the ZD stiffness influence the forces that create cracks. It was observed that decreasing the ratio of hard-wood-to-softwood content and reducing the amount of starch would both decrease crease cracking.

Cracking at the fold of publication and packaging paper grades is a serious problem that can lead to rejection of product. Recent work has revealed some basic mechanisms and the influence of various parameters on the extent of crack area, but no studies are reported using coating layers with known mechanical properties, especially for double-coated systems. In this study, coating layers with different and known mechanical properties were used to characterize crack formation during folding. The coating formulations were applied on two different basis weight papers, and the coated papers were folded. The binder systems in these formulations were different combinations of a styrene-butadiene latex and mixtures of latex and starch for two different pigment volume concentrations (PVC). Both types of papers were coated with single and double layers. The folded area was scanned with a high-resolution scanner while the samples were kept at their folded angle. The scanned images were analyzed within a constant area. The crack areas were reported for different types of papers, binder system and PVC values. As PVC, starch content, and paper basis weight increased, the crack area increased. Double layer coated papers with high PVC and high starch content at the top layer had more cracks in comparison with a single layer coated paper, but when the PVC of the top layer was low, cracking area decreased. No measurable cracking was observed when the top layer was formulated with a 100% latex layer.

In this paper, white pixel percentage (WPP) value, as an overall measure of fold crack damages, has been analysed with respect to selected parameters of sample preparation and digitalization process, as well as the results of residual tensile strength. The WPP values were derived by an automated image processing algorithm, developed earlier, based on extensive comparative analysis of the existing computer-aided methods. Results indicate that WPP values correlate well with the extent of fold cracks on the coated samples, as far as the used parameters of sample preparation and digitalization are concerned. In the case of correlation with residual tensile strength, results for samples folded in cross direction revealed that the extent of the visually registered fold cracks agree well with the actual damage, while for samples folded in machine direction, the overall strength losses weren’t alarming, although the fold cracks were detected correctly. In addition, results pointed out that the simplest sample placement position (inner angle of 180°) is not applicable for realistic sample representation. Furthermore, scanners could provide a superior image quality in lab conditions, but for industry application, a camera-based solution would be more purposeful, while micrographs are more suitable for traditional visual analysis.

Two suction rolls at the first press section of a 25 ft. wide paper machine developed cracks within two years of service. The rolls were austenitic stainless steel castings made of ASTM A 351 Grade CF8M alloy containing molybdenum. The rolls were exposed to slightly acidic white water (pH approximately 4.7) containing chlorides (45 ppm). Visual and liquid penetrant inspections of the rolls revealed extensive cracking at the roll inside surface. The cracks penetrated more than 30 percent of the wall thickness and a few cracks were several inches long. The cracks were preferentially oriented along the roll length and primarily at the roll inside surface. Field metallographic examination showed significant grain boundary chromium-carbide precipitation and intergranular corrosion. The roll failures were attributed to chromium depletion along the grain boundaries (sensitization) resulting from slow cooling of the casting to avoid large residual stresses. The roll manufacturer recommended a proprietary ferritic/austenitic stainless steel as the replacement material for the rolls.

Fold cracking is one of quality troubles of coated papers. In this study, the fold cracking of high grammage 2(250 g/m) coated paper made with the different pulp composition and layer structure of base paper was investigated. The single layered, high grammage base paper was prepared by mixing of hardwood and softwood bleached kraft pulp fibers with the different ratios. The high grammage coated paper showed the higher fold cracking than low grammage coated paper because of the increase in thickness. The increase in the content of softwood pulp fibers reduced the fold cracking in the case of high gram-mage coated paper. When the creasing process was conducted before folding process, the fold cracking of coated paper decreased. By manufacturing the base paper with multiply structure, the fold cracking of coated paper could be reduced significantly, especially when the BCTMP and OCC were used as a middle layer and the creasing process was car-ried out. The delamination of layers in base paper affected the fold cracking positively. Keywords: Fold cracking, coated paper, high grammage, multiply structure, creasing

High loading of base paper is regarded as one of reasons to aggravate fold cracking of coated paper. But the relationship between the ash content of base paper and fold cracking of coated paper has not been shown yet. We investigated the effect of ash content in base paper on the fold cracking of coated paper. Handsheets with three different ash contents (19.5-23.5%) were prepared, and double layered coating were applied on the top side of the handsheets. A gravimetric water retention meter (AA-GWR) was employed to fold the paper with a uniform pressure after solid printing on the coated surface. The fold cracking was digitized by calculating the cracked area by means of an image analysis technique. Results suggested that high ash content in the base paper increased the fold cracking of the outer surface of coated papers. In the case of inner surface greater fold crack areas were obtained, and the number of cracks decreased because long and wide cracks were formed. Reduction in tensile strength and thickness appeared to give greater fold cracking for highly loaded papers.

Paper-based asphalt felt, which is typically used as a waterproofing material, is one of the most problematic solid wastes in terms of disposal and environmental contamination. The laboratory work presented in this paper aims to propose a strategy for utilizing the reclaimed paper-based asphalt felt (RPAF) waste in hot-mix asphalt (HMA) pavements as a means to mitigate the RPAF disposal problem. A series of laboratory tests, including viscosity, modulus, rutting, and cracking, were conducted to investigate the effects of RPAF additives on the engineering performance of asphalt-binder and HMA mixes. The corresponding test results showed that the addition of RPAF improves the viscosity and high-temperature performance of asphalt-binders. However, RPAF modified asphalt-binder exhibited inferior storage stability than the virgin asphalt-binder due to the difference in density between the asphalt-binder and RPAF components. Additionally, the effect of RPAF on the rheological characteristics of the asphalt-binder exhibited high sensitivity to temperature. The differences in complex modulus and phase angle of the asphalt-binder with RPAF additives were generally more significant at elevated temperatures. Similarly, RPAF modified HMA mixes outperformed the control HMA mix in terms of resistance to moisture damage, rutting, and cracking, respectively. Overall, the laboratory test results indicated that it is feasible to utilize RPAF waste as an asphalt-binder modifier to enhance the engineering properties/performance of the asphalt-binder and HMA mix whilst simultaneously addressing the environmental issues of RPAF waste disposal.

Fatigue cracking is a major distress in hot mix asphalt (HMA) pavements. The coalescence of microcracks into macrocracks has been widely recognized as a prevalent cause of fatigue failure i...

Co-pyrolysis and CO2 co-gasification of paper and polystyrene blends in different mixture ratios were studied at 1173 K using a laboratory scale tube reactor and thermogravimetric analysis. The chemical composition and yield of the syngas produced was analyzed by a micro gas chromatograph to understand the influence of mixture components. Co-pyrolysis positively impacted the syngas yield exhibiting a synergistic influence on cracking reactions leading to increased gaseous yield having almost double the amounts of hydrogen yield. Co-gasification using CO2 increased the total gas yield with enhanced synergistic conversion. This effect provided a non-linear impact on the combustible gases in the gaseous yields when compared to the separate gasification of these feedstocks. The synergistic enhancement of co-pyrolysis conversion in paper-polystyrene led to lower char present for CO2 to react during CO2 co-gasification that lead to lower CO during the gasification of this blended char residue. The mixtures of paper with polystyrene provided increased product gas yields and enhanced conversion with an increase in polystyrene content. The results showed the effectiveness of producing high energy density syngas from co-gasification which can alleviate material handling issues present in segregation of waste, such as plastics and biomass providing uniform valuable product from diverse waste feedstocks with minimal need for classification.

Currently, thousands of kilometers of pipeline steels are transferring hydrocarbon fluids such as oil and natural gas in the world. Due to the fact that these pipes transport corrosive and high-pressure fluids from harsh environments, they are damaged and eventually degraded. Previous studies showed that sulphide stress cracking, hydrogen induced cracking (HIC) and stress corrosion cracking are the main destructive factors in these types of pipes. This paper focused on the HIC related failure in pipeline steel, since the role of texture and grain boundary character has not been completely recognized. Moreover, if pipeline damage is occurred by hydrogen cracks, besides the environmental pollutions, it will cost a lot to repair or replace the damaged pipeline steels. In this research, the factors influencing the initiation and propagation of the HIC cracks, such as hydrogen traps, inclusions, precipitates, microstructure and texture of steel have been investigated. Also, the existing solutions for improving the steel resistance to the HIC have been investigated based on the control of micro-alloy elements, texture and grain boundary engineering. For instance, some special dominant texture components and coincidence site lattice boundaries decrease the HIC susceptibility by providing the resistant path for crack propagation.

High ash-containing paper sludge ash (PSA) has been investigated in terms of its use as a low-cost catalyst for primary pyrolysis tar cracking in the two-stage pyrolysis of biomass. Experimental results showed that tar yields decreased significantly using PSA as catalyst in comparison with the thermal cracking experiments. A consequent increase in total gas yield was obtained. The yields of H2, CH4, and CO2 increased significantly under the catalytic effect of PSA, particularly the H2 yield almost doubled, while CO yields showed a slight decrease due to the consumption reactions. Thermogravimetric analysis of the fresh and spent PSA showed that carbon particles formed along with the tar decomposition, while the catalytic reactivity of the PSA was not reduced because of the participation of carbon particles in tar reforming. XRD spectrograms revealed that calcium-ferrite oxide (Ca2Fe2O5) was formed in PSA, which has excellent stability and catalytic effect on tar cracking and H2 production. The PSA still s...

Fold cracking of coated papers has become important because of the increase in the coat weight and the content of low cost co-binder. The effects of base paper characteristics of coated paper were investigated to reduce fold cracking. We evaluated the fold cracking of coated paper prepared with different mixing ratios and beating degrees of pulp fibers. Hardwood bleached kraft pulp (Hw-BKP) and softwood bleached kraft pulp (Sw- BKP) were used to prepare base papers for coating. The mechanical and structural properties of base paper such as tensile strength, strain at break, short span compressive strength, and formation were measured. The fold cracking was affected by mixing ratio of pulp fibers. Base paper consisting of Hw-BKP and Sw-BKP at a 90:10 mixing ratio showed the least fold cracking. When the amount of Sw-BKP was greater than 10% or if only Hw- BKP was used, the fold cracking increased on coated paper. When the pulp was highly beaten, the mechanical strength of paper was improved, but the fold cracking was severe. An increase in the tensile strength did not reduce the fold cracking.

In order to improve structural efficiency, environmental performance, and constructability, a new type of one-way composite voided slab system (TUBEDECK) has been recently proposed which combines profiled steel decks with cast-in-situ RC slabs. Because eliminating concrete volume to optimize flexural strength can significantly reduce the shear strength of nonprestressed concrete or composite slabs without shear reinforcement, a clarification of the shear resistance capacity is required. In this study, shear tests on a total of 12 specimens were conducted with slab thickness, the presence or absence of voids and/or steel decks, and tension reinforcement ratio as variables. The results show that combined flexure and shear dominated the behavior of both voided (V) slabs and TUBEDECK (TD) slabs, and web-shear cracking did not affect strength. Predicted shear strength based on the minimum web width was too conservative. Conversely, the shear strength prediction equations, which were proposed on the basis of the real cross-sectional area of concrete, predicted the capacity of both V slabs and TD slabs from a reasonably conservative perspective. A discussion on the influence of moment–shear interaction is also included, and an interaction design model is proposed in a further investigation.

Deterioration of the quality of oilstock makes it an urgent problem to use non-traditional hydrocarbon materials (heavy oil, bitumen, residues etc.). Processing of heavy oilstock (HOS) needs new methods that would be effective for the yields of light fractions, suppression of coke formation, and saturation of the liquid products with hydrogen. At the same time, expenses of HOS extraction and transportation are several times as high as those of light and middle oils that makes it necessary to minimize the capital and operational costs for the process. The review paper integrates for the first time the results of the studies of catalytic steam reforming of HOS as a potential alternative of the traditional processes for HOS upgrading based on decreasing the carbon content (thermal cracking, visbreaking, catalytic cracking) or on the saturation of liquid products with hydrogen (hydrocracking). Under discussion are main distinctions of the process from HOS upgrading with water (hydropyrolysis in sub- or supercritical water) as well as specific features of the catalytic steam cracking as dependent on the process parameters and catalysttype and putative mechanisms of the participation of water in the process.

Failure analysis of a paper machine duplex stainless steel suction roll material demonstrated that the mechanism of failure was intergranular stress-corrosion cracking followed by fatigue. Crack initiation was related to both the heat treatment of the alloy and the chloride content developed in the system during paper machine shutdowns. Crack propagation occurred during normal operating conditions by a corrosion fatigue mechanism.

Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the n ...

Tribocorrosion behaviour of thermally sprayed cermet coatings: WC-CoCr deposited by HVOF and HVAF and Cr3C2-WC-NiCrCo applied by HVAF, was examined in paper machine environment in a pin-on-disc tribometer under the load of 20 N in electrolyte containing chlorides and sulphates, pH 4.5. Wear was the dominant degradation mechanism for all coatings, followed by corrosion-induced wear, the importance of which increased with rising potential. The overall material losses were lowest for HVAF WC-CoCr and highest for HVAF Cr3C2-WC-NiCrCo, the latter being related to the evident abrasive wear of the Cr3C2 phase and cracking along Cr3C2-matrix interface in the near-surface areas. Among the three coatings, contribution by corrosion to the damage was greatest in HVOF WC-CoCr, likely due to high degree of porosity.

Voided slab construction is a way of effectively removing concrete from middle section of a RC slab which has not a structural function, thereby reducing structural dead weight. Voided slab construction has advantages such as reducing self-weight, Cost efficiencies and fast Construction. However, floor stiffness of voided RC slab is less than its solid counterpart and there is gap in literature about structural behaviors of voided RC slabs. This research work presents experimental and numerical investigations of voided RC slab. Six solid and voided RC slab specimens of size 800mmx300mmx200mm were casted and tested until failure under one-point load. Also, leveraging advantages of FEA, effect of influential variables such as void size, loading type, concrete compressive strength, and effect of top reinforcement were thoroughly studied. Experimental test results indicated as compared to control solid RC slab, 60mm diameter paper tube voided RC slab exhibited 12%, 15.54%, 25.50%, 14.64% and 6.71% loss in strength, cracking load, stiffness, ductility, and toughness respectively where as for 90mm diameter paper tube voided RC slab respective values were 20%, 19.87%, 38.80%, 25.50% and 12%. Also, as void size increased from 60mm to 90mm, voided slab failure mode changed from flexural to shear. Finally, FEA, ACI 318M-19 and EC2 codes showed good agreement with experimental results.

In operation, the insulation paper used for transformers is subject to electric stress. This paper may deteriorate as a result of the accumulation of mechanical stress and the polarisation of the electric field. The effect of electric fields on insulation paper is typically investigated through macroscopic tests; thus, the microscopic mechanism must be explored further. In this study, single- and multi-chain cellulose models were constructed to simulate the yield behaviour of cellulose under a strong electric field (1010 V m− 1) through molecular dynamics. The cracking process of insulation paper was also examined according to density functional theory. Results indicated that both single- and multi-chain celluloses yield under a strong electric field. This yield behaviour is consistent with that of the electric field, and it eventually breaks the cellulose chains. The energy gap between the lowest unoccupied and the highest occupied molecular orbitals suggested that cellulose molecules may encounter insul...

The mechanical behaviour of coated papers during folding has been investigated. This problem has been studied with experimental techniques and numerical analyses in order to give a better understanding of the folding properties of coated papers pertinent to the mechanical behaviour in general, and particularly cracking along the fold. A microscopy investigation has been performed. The surface of the folded paper has been carefully examined to study the event of fracture and related issues. The influence of the grammage on the cracking event has been studied and it was shown that the coating material would not fail if the paper sample was sufficiently thin. It was found that a stress or strain based criterion is sufficient to describe the cracking of the coating layers and that the anisotropy of paper should be taken into account when studying the folding process. The finite element method has been used for the numerical analyses remembering that the geometry of the problem is rather complicated, excluding a solution in analytical form. Using different constitutive models for the base stock, it has been shown that the deformation of the coated paper during folding is much governed by the paper substrate. The numerical results also suggested that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. Furthermore, it has also been shown that delamination buckling, in the present circumstances, has a very small influence on the strain levels in the coating layer subjected to high tensile loading. Dynamic effects have also been studied and it has been shown that a quasi-static analysis of the problem is sufficient in order to describe many of the important features related to cracking. An attempt to model strong anisotropy of paper has been presented and the results indicate that the large anisotropy in the thickness direction of coated papers needs to be taken into account in order to fully understand the mechanics of folding. Finally, an experimental investigation has been presented in order to study if important mechanical properties of the coating material could be determined by microindentation techniques. The results presented indicate that microindentation can be a powerful tool for characterization of these materials, but only if careful efforts are made in order to account for the influence from plasticity as well as from boundary effects. KEYWORDS: folding, coated papers, finite element method, cracking, indentation, anisotropy, plasticity.

In this paper, we present the results of mechanical testing that reveals the onset crack strain and fatigue crack growth of TiO2 and Al2O3 films deposited by atomic layer deposition. Data show that both films have a strong thickness dependence of the onset crack strain, with the strain reducing with increasing film thickness. Additionally, TiO2 films have a lower onset crack strain and strain for fatigue damage than Al2O3. However, TiO2 films are more resilient in harsh environments where fatigue damage in Al2O3 films grows faster.

Black liquor recovery boilers are essential components of kraft pulp and paper mills because they are a critical element of the system used to recover the pulping chemicals required in the kraft pulping process. In addition, the steam produced in these boilers is used to generate a significant portion of the electrical power used in the mill. Recovery boilers require the largest capital investment of any individual component of a paper mill, and these boilers are a major source of material problems in a mill. The walls and floors of these boilers are constructed of tube panels that circulate high pressure water. Molten salts (smelt) accumulate on the floor of recovery boilers, and leakage of water into the boiler can result in a violent explosion when the leaked water instantly vaporizes upon contacting the molten smelt. Because corrosion of the conventionally-used carbon steel tubing was found to be excessive in the lower section of recovery boilers, use of stainless steel/carbon steel co-extruded tubing was adopted for boiler walls to lessen corrosion and reduce the likelihood of smelt/water explosions. Eventually, this co-extruded or composite (as it is known in the industry) tubing was selected for use as a portion or allmore » of the floor of recovery boilers, particularly those operating at pressures > 6.2 MPa (900 psi), because of the corrosion problems encountered in carbon steel floor tubes. Since neither the cause of the cracking nor an effective solution has been identified, this program was established to develop a thorough understanding of the degradation that occurs in the composite tubing used for walls and floors. This is being accomplished through a program that includes collection and review of technical reports, examination of unexposed and cracked tubes from boiler floors, computer modeling to predict residual stresses under operating conditions, and operation of laboratory tests to study corrosion, stress corrosion cracking, and thermal fatigue.« less

Given sufficient anchorage to the diaphragms, out-of-plane walls in unreinforced masonry (URM) buildings have been shown to crack above midheight and then rock as two rigid bodies. This study investigates the sensitivity of the rocking response to the type of ground motion and the quality of the wall construction. Shake table tests were conducted on four full-scale multi-wythe walls, all with a height to thickness (h/t) ratio of 12 but of varying construction quality and subjected to three different ground motions. All walls experienced cracking at less than one half of the 2005 National Building Code of Canada (NBCC) level for Vancouver, but exhibited a stable rocking behaviour without collapse beyond a ground motion 1.5 times the 2005 NBCC level.

Brightness, opacity, surface strength, ink density, and cracking tendency were not affected by the layout strategy for drying the precoat. Dryer capacity and economic aspects should be considered more than questions about quality in optimizing the precoating installation.

Fiber Reinforced Plastics (FRP) are increasingly applied in transportation systems (aircraft, railway, automotive) and infrastructure industries due to the good specific properties of high strength at low weight. Advanced FRP structures have to endure high mechanical and environmental loading. Therefore the durability and reliability depends much more on the micro mechanical properties as on the global strength. X-ray refraction topography is a powerful tool for the characterization of inner surfaces in materials. Applied to fiber composites the presented investigations give information about the mean diameter of the fibers, orientation and the quality of impregnation. Strong correlations were found between fiber matrix debonding and micro cracking and the stress state due to mechanical loading. Additionally a new method for a quantitative determination of transverse and shear strength in a complex laminate is presented. Therefore the X-Ray refraction technique is applied on-line during tensile load of specimens.

The possible influence of the so-called Rock-Eval matrix effect on the determination of the kinetic constants of kerogen cracking has, besides its scientific interest, important practical implications. Unfortunately, the experimental results obtained by Dembicki were incorrectly processed, resulting in incorrect conclusions. A more correct treatment of the data leads to the important conclusion that, as a first approximation, a mineral matrix has no influence on the kinetic interpretation of Rock-Eval experiments. This enables measurements to be made directly on whole rocks, thus avoiding the expensive preparation of kerogens. Finally, in order to make meaningful comparisons between kinetic studies, it is suggested that geochemists agree on a common, universal value of the frequency factor A in the Arrhenius form of first-order rate constants.