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Abstract

In built environments the combustibility of wood is a great concern, which limits the use of wood as a building material due to legislation. The reaction-to-fire properties of wood can be altered with the use of fire-retardant chemicals, and most of the commonly used fire retardants already have a long history of use. However, only limited information is available on the impact of different fire retardants on the adhesion properties of wood. Additionally, comparative studies between chemicals from different groups of fire retardants is scarce. The objective of this study was to investigate and compare the effects of two commonly used fire retardants, sodium silicate (SS) and diammonium phosphate (DAP), on veneer properties, the focus being especially on thermal behavior and adhesion. Thermal properties and combustibility were studied using thermogravimetric analysis (TGA), flame test and calorimetry. Glue bond strength was analyzed with an automated bonding evaluation system (ABES) and the leaching of chemicals was determined according to EN84. Additionally, the surface characteristics of modified veneers were imaged with scanning electron microscopy (SEM). Results revealed notable differences in the thermal properties of SS and DAP, with DAP having better fire-retardant performance in all thermal testing. SS also affected thermal properties and combustibility of modified veneers, but the effect was only moderate compared to DAP. Neither SS or DAP had any significant resistance against leaching but ABES testing showed a notable increase in the glue bond strength of DAP modified veneers.

Abstract

Carbon footprint over the life cycle is one of the most common environmental performance indicators. In recent years, several wood material producers have published environmental product declarations (EPDs) according to the EN 15804, which makes it possible to compare the carbon footprint of product alternatives. The objective of this study was to investigate the effect of service life aspects by comparing the carbon footprint of treated wood decking products with similar performance expectations. The results showed that the modified wood products had substantially larger carbon footprints during manufacturing than preservative-treated decking materials. Replacement of modified wood during service life creates a huge impact on life cycle carbon footprint, while maintenance with oil provided a large contribution for preservative-treated decking. Hence, service life and maintenance intervals are crucial for the performance ranking between products. The methodological issues to be aware of are: how the functional unit specifies the key performance requirements for the installed product, and whether full replacement is the best modeling option in cases where the decking installation is close to the end of the required service life.

Abstract

The medium-consistency (MC) pump is the key unit in modern pulp and paper industry, especially in medium-consistency bleaching plant. Use of MC pump improves the efficiency of bleaching sequences and reduces the pollution load of bleaching effluents. In this work, the component of MC pump, e. g. turbulence generators with three typical structures were studied to evaluate the effects of turbulence generator structure on the performance of MC pump. An automatic control system was built to control operation condition and to collect data online. Head and efficiency were calculated to evaluate the differences among three turbulence generators. The results showed that the linear-type, twist-type and screw-type turbulence generators exhibited similar performance (pump head and efficiency) of MC pump at high rotation speed (2000 rpm to 2900 rpm) compared to the well-known performance of MC pump at rotation speed lower than 2000 rpm which are significant different for the three turbulence generators.

Abstract

Acetylated wood is a durable and dimensionally stable product with many potential applications in exterior timber structures. Research has shown that acetylated wood can be effectively bonded by various adhesive types. However, one of the most commonly used adhesives for timber constructions, melamine urea formaldehyde (MUF), shows poor performance in combination with acetylated wood in delamination tests based on cyclic wetting and drying. The hydrophobic acetylated wood surface leads to reduced adhesion due to poorer adhesive wetting and fewer chemical bonds between the resin and the wood polymers. The use of a resorcinol-formaldehyde (RF)-based primer on the acetylated wood surface prior to the application of MUF leads to positive gluing results with both acetylated radiata pine and beech, providing significantly improved resistance to delamination. Radial penetration of the primer and MUF in acetylated wood shows higher penetration compared with untreated wood. In addition, a phenol resorcinol-formaldehyde adhesive system showed high resistance against delamination and can be used for gluing of acetylated wood.

Abstract

Increasing the filler content of sheet tends to decrease filler retention and paper strength properties. To overcome this problem and make better use of fillers, development of new methods on filler modification has never been stopped. In this study, filler modification was carried out by sequentially adding an anionic polyacrylamide, a cationic starch and a cationic polyacrylamide. It is believed that in this process, multiple polyelectrolyte complexes are formed which can not only encapsulate filler particles but also preflocculate the particles. The results showed that, compared to the single preflocculation treatment, the sequential encapsulation and preflocculation (SEP) treatment brought significantly larger particle size and higher surface charge potential of the filler, thus higher filler retention was achieved. When the modified fillers were used for papermaking and paper ash contents were controlled at the same level, the SEP modification was better in improving the tensile index, internal bond strength and tearing index of paper than the single preflocculation method, in addition, it maintained better paper formation, caused insignificant change on opacity of paper. It is believed that this newly developed SEP method is worthy of being applied to industrial scales in making various grades of filled paper.

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Abstract

This study is the first, to the best of our knowledge, where waste napkin paper was successfully valorized to low-density (27.2 mg cm−3) cellulose aerogels for oil sorption material. Two simple methods with different gel coagulators, ethanol and sulfuric acid, were used for preparation of the aerogel. Conditions for the alkaline treatment of the raw material and the pre-freezing temperature in the lyophilization process were optimized. It was found that the water and oil sorption capacities of the aerogels were not significantly affected by alkaline treatment, while they could be adjusted by changing the pre-freezing temperature. Although the produced aerogels were initially amphiphilic, hydrophobic surfaces were obtained by vapor deposition of methyltrimethoxysilane (MTMS) and these materials possessed high sorption capacities, up to 32.24 cm3 g−1 (28.56 g g−1) for pump oil and 26.77 cm3 g−1 (39.59 g g−1) for chloroform. This was comparable to aerogels prepared from fresh cellulosic materials via the sol-gel method, as their sorption capacities varied in the range of 14–45 g g−1.

Abstract

Durable papers should exhibit high mechanical strength and good soiling resistance. In this study, cellulose nanofibrils (CNF) was investigated as an additive to the polyvinyl alcohol (PVA) impregnation solution to improve the durability of paper. The impregnation suspensions were prepared by adding CNF to PVA solution in various ratios, and were used to impregnate a base paper. The PVA-CNF suspensions exhibited good dispersion stability; however, the low shear viscosity increased as its CNF content increased. The pickup weights of the papers impregnated with the PVA-CNF suspensions were found to be lower than those of the control sample, which were impregnated with the pure PVA solution only. Although the strength of the paper was not significantly improved by the addition of CNF, when the paper was impregnated with a PVA-CNF suspension containing 5 % CNF content, the product exhibited similar strength to the papers impregnated with only a 3 % PVA solution despite its lower pickup weight. The mechanical strength of the impregnated paper was affected by the pickup weight and penetration of the impregnating agent. The addition of a wet strengthening agent to the mixed suspensions was seen to enhance the wet soiling resistance of the papers.

Abstract

In this work, the American Old Corrugated Containers (OCC) pulp was screened using pressure screen to investigate the factors affecting the fractionation performance. Three screen cylinders with different geometries, aperture size/contour heights, volumetric reject ratios, and aperture velocities were used. The results showed that the passing ratio of fibres increased with the increase of contour height, volumetric reject ratio, and aperture velocity for all the three screen cylinders. Moreover, among the three cylinders investigated, the 0.81 mm hole cylinder achieved the highest fractionation efficiency with a volumetric reject ratio of 0.1 followed by 0.15 and 0.2 mm slot screens. Freeness change of the accept side of the screen was similar to passage ratio, which shows an increasing trend with the increasing aperture velocity and volumetric reject ratio. However, the reject freeness showed decreasing trends with the increasing aperture velocity Vs and volumetric reject ratio Rv.