Volume 34, Issue 4

Functionalized paper solutions have attracted the attention of many research groups in the 21st century, given the low cost, availability, flexibility and biodegradability of paper. Despite this material has been manufactured for more than two thousand years, its traditional uses hardly go beyond writing, printing, cleaning and packaging. This overview covers fascinating advances in the functionalization of paper that have taken place this century. This century, test strips for glucose and pH have evolved towards microfluidic paper analytical devices that allow for accurate quantitative determinations. In another context, paper electronics started with the first paper-based transistors and followed with more sophisticated electronic devices. Also, cheap paper-based membranes and adsorbents have been proposed for water treatment, and researchers have found innovative ways to confer antimicrobial and anti-counterfeiting properties to paper. Furthermore, numberless ways to functionalize paper are reported here. Fibers can be modified by chemical reactions, nanofibrillation or supramolecular interactions with certain reagents. The surface can be coated by diverse methods, including size press coating, sputtering, e-beam evaporation and the sol-gel process. Special inks can be printed onto paper to make hydrophobic, conductive or luminescent patterns. Brief opinions about future outlooks are given at the end.

Kadam is a fast growing tree species in Bangladesh. The main aim of this study is to observe the influence of tree age of kadam on chemical pulping. In this research 8, 18 and 30 years old kadam wood were pulped under different active alkali of 16, 18 and 19 % maintaining 25 % sulphidity and its effect on chemical composition, kappa number, pulp yield and delignification was investigated. The result shows that the content of extractive, lignin, alpha-cellulose and hemicellulose increase to different content along with the increase of tree age. There are also some differences of pulping properties with different tree age. Pulp yield of 8 years old kadam is higher than other ages of kadam trees. The hand sheets were made and the physical strength properties likely tear, tensile and burst were evaluated at two freeness level. The pulps produced from 8 year kadam tree obsessed reasonable strength properties. These could be used for producing moderate quality writing, printing and wrapping papers. Pulp wood of 8 years kadam is more suitable for pulping, compared to that 18 and 30 years.

Bagasse fiber has been used in the production of bleached chemical pulp by the Pars Paper Company. In this company, a conventional three-stage sequence of hypochlorite, alkaline extraction and second hypochlorite (HEH) is applied in pulp bleaching. Pulp bleaching is one of the most important environmental pollutant stages in the pulp and paper industry. In this research, the bleaching of soda bagasse pulp by applying Oxone and TAED-activator in non-chlorine bleaching sequences has been investigated. The unbleached pulp, with kappa number of 20, 955 ml/g viscosity and 37 % brightness, was prepared from Pars Paper Company. Results indicated that, the TAED at the first and second stages were more effective than in the Oxone stages. Moreover, the sequences, which contained TAED- and Oxone-second-stage, could reach the minimum level of kappa (1.7), but the highest brightness (80 %) was attained by using only TAED with a comparatively high level of pulp viscosity (752).

To be able to charge a correct amount of chlorine dioxide in the D 0 -stage, a pulp mill needs good control of the bleaching process and good sensors to keep the variability of the bleaching result on an acceptable level. It is also important to include the bleaching agent demand from the dissolved matter in the pulp slurry. If this is done correctly, over- or undercharging of bleaching agents can be reduced, which lead to lower bleaching chemical cost, lower polluting emissions and higher pulp quality. Our previous research has shown that the dissolved organic carryover from the O 2 -stage varies significantly when bleaching softwood kraft pulp. The present study investigated the corresponding impact in the case of bleaching of birch pulp. Different mill configurations and process conditions have been simulated in laboratory trials, including proceeding A-stage treatment, different degrees of washing before and between the stages, and a comparison of the effects of recycled and non-recycled wash filtrates. The results have confirmed the significant impact of the dissolved organic matter, and the knowledge which have been generated can be used to understand how measurement and control concepts can be developed to improve the pulp quality control and to decrease production cost.

Surface characterization is important and has many applications in the paper industry. It includes both surface roughness and surface friction. In determining the surface roughness of paper and paperboard, non-contact methods such as air-leak methods In characterizing the surface roughness of paper and paperboard, it has been a common practice that the average roughness with the coefficient of variation (COV) has been conventionally determined. This practice, however, this runs the risk of drawing wrong conclusions since two different surfaces having the same average roughness and COV can exhibit totally different properties. To avoid such mistake, a stylus-type contact method has been developed to determine surface roughness of paper and paperboard such as printing & writing (P&W), kraft and liners. In this method, surface roughness profile has been generated to determine its variability which has been defined as the mean deviation from the roughness average, referred to as MDRA. In determining the MDRA, it is noted that thickness measurement is not required. In this method, stylus shape and size, contact force of the stylus to the surface, scan speed and resolution have been identified as the key parameters of generating stable surface roughness profiles. It has been further identified that the optimal conditions on these parameters should depend on paper grade. It is suggested that a stylus-type contact method should be used to determine surface roughness of paper and paperboard to help determine their practical applications such as printing, coating and embossing.

The potential use of sago pith waste, bamboo, and water hyacinth based on the characteristics of raw materials to make liner paper were studied. The analysis conducted covered the analysis of physical characteristics, chemical components, morphology (SEM), functional groups (FTIR), and crystallinity (XRD). The pulp from the three kinds of fiber was molded into paper with a certain formulation. The parameters of pulp and paper observed covered the alkaline consumption, Kappa number, pulp yield, and paper physical characteristics (grammage, bursting strength, Ring Crush Test/RCT, water content, and water absorption). The chosen paper was the paper whose characteristics resembled the quality parameter of liner paper used by the paper industry and the standard in accordance with the Indonesia’s National Standard (SNI) 14-0095-1996. The microscope images showed that the three said raw materials have long fibers: sago pith waste and water hyacinth has fibers measuring respectively 1.89±0.90 and 2.07±0.39 mm, resembling hard wood, whereas bamboos have longer fibers measuring 4.61±0.72 mm, resembling soft wood. Bamboos have the best fiber composition and characteristics for pulp and liner paper. The two paper formulas that meet the criteria for liner paper are bamboo and bamboo+water hyacinth.

In the present study, antibacterial paper was prepared by mixing chlorhexidine with modified galactomannan. The effects of the oxidation time and citric acid dosages in the modification processes on the physical properties of the paper samples were examined. Also, the effects of the antibacterial agent dosages on the antibacterial properties were studied. The results showed that when the oxidation time was 5 hours, the tensile index, bursting index, and folding endurance increased by 18.4 %, 31.9 %, and 200.0 %, respectively, when compared with the control paper. Also, when the amount of citric acid was 7 %, the tensile index, bursting index, and the folding endurance increased by 20.3 %, 36.6 %, and 195.1 %, respectively, when compared with the control paper. The paper with two modified polysaccharides displayed antibacterial properties against Escherichia coli and Staphylococcus aureus . This study’s elemental analysis results indicated that when the amount of chlorhexidine was 2 %, its retention in paper with oxidized or esterified galactomannans was 1.74 % and 1.59 %, respectively. Furthermore, the SEM results showed that the structures of the bacteria around the inhibition zone were damaged and their activities had been inhibited.

Cellulose fibers swell significantly in NaOH/urea solutions, and swelling increases with a decrease in temperature and an addition of urea. The combined effects of the factors of a pretreatment procedure (sodium hydroxide concentration, urea concentration, temperature, and time) and post-treatment conditions (medium, stirring speed, and time) of preparing fibers on the properties of pulp and the resulting paper sheets were investigated and optimized using single factor experiments. The optimum sodium hydroxide concentration (1 %), urea concentration (8 %), precooling temperature 0 °C, pretreatment time (12 h), post-treatment medium (7 % (NH4)2SO4{({\mathrm{NH}_{4}})_{2}}{\mathrm{SO}_{4}}), post-treatment stirring speed (1500 rpm), and time (30 min) were obtained. Under the optimal conditions, the water retention values and tear, tensile, and burst indexes increased about 54 %, 277 %, 394 %, and 98 %, respectively. This work demonstrates that this technical route can effectively improve fiber swelling capacity and paper strength.

Paper relics are important historical and cultural heritages. However, the paper relics are at risk of ageing, damage and disappearance. In order to delay the aging of paper, improve the strength of paper, solve the problem of poor permeability and stability of traditional resins to paper, the polyurethane was synthesized by polydimethylsiloxane (HTPDMS) and low molecular weight hexamethylene diisocyanate (HDI) trimer, and the chemical and physical properties of paper samples were tested. Results showed the paper coated by HTPDM-modified polyurethane liquid had good mechanical property, the tensile strength was increased from 1105 to 3299 N/m, the folding endurance was increased from 20 to 1024; and had good gloss and brightness; after thermal aging, coated paper can effectively maintain tensile strength, delay folding resistance and tearing strength loss; after acid stability test, the loss ratio of tensile strength was decreased from 34.2 % to 15.7 %, folding endurance was decreased from 57.1 % to 9.7 %; after alkali stability test, the loss ratio of tensile strength was decreased from 29.3 % to 6.6 %, folding endurance was decreased from 82.9 % to 22.0 %. Therefore, the prepared polyurethane material has great application prospects in the protection of paper.

Ionic liquids (IL) of 1-butyl-3-methylimidazolium chloride (BmimCl) homogeneously mixed with bleached kraft pulp (BKP) were used to investigate the change of paper properties and refining performance under the general conditions. Fiber morphology and paper strength were determined by fiber analyzer and paper physical property tester. The surface morphology and chemical properties of fiber was also performed by scanning electron microscope (SEM), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated the optimized conditions of BmimCl pretreatment were BmimCl dosage of 1.5 mL/g, the time and temperature of 30 min and 80 °C, respectively. The physical properties of paper and internal bond strength of fiber was improved by BmimCl pretreatment. BmimCl pretreatment facilitated swelling and fibrillation of fiber, increased the crystalline index of fiber and decreased the lignin and extractives on the surface of fiber, which leading to improve fiber strength and tensile strength. For the same refining energy input, saving the maximum refining energy consumption was 14.0 % after BmimCl pretreatment, which is beneficial to improve the application of ionic liquid in pulp and papermaking.

Food packaging is the most important output of the printing industry. Giving antibacterial effect to the papers used in food packaging will extend the shelf life of the product and food transfer in healthier conditions. The nanoparticles with known antibacterial activity are nanosilver, nanogold, nanosilica. Binders used in paper coating provide a good nutrient medium for bacteria. In this study, Ag nanoparticles was first synthesized as monodisperse in 10 nm size with polyvinyl pyrrolidone and sodium boron reaction which will give antibacterial properties to paper coatings. The chemical structure of the synthesized Ag nanoparticles is illuminated by fourier transform infrared spectrophotometer (FTIR). Different paper coating formulations containing varying amounts of Ag nanoparticles were prepared with starch binder. Using these mixtures; papers coated with a laboratory-type paper coating machine onto 80 g/m 2 paper. Color, gloss, contact angle, surface energy, antibacterial properties of the paper against the E. coli bacteria and S. aureus bacteria were examined. As a result, Ag nanoparticles has been successfully synthesized and used in paper coating. Antibacterial and printability properties were improved by increasing the amount of Ag nanoparticles.

Due to the micro-sized pores on cellulosic substrate surface and the hygroscopic nature of cellulosic fibers, paper has poor barrier properties. Dispersion coating can improve the barrier properties of cellulosic paper noticeably by forming a continuous, non-porous polymer film on paper surface. In this work, the excellent film-forming performance of polyvinyl alcohol (PVA) was used to seal the surface pores of paper, thus enhancing the barrier properties. Alkyl ketene dimer (AKD) was also added as a coating component to improve the water resistance of paper. Results showed that after PVA/AKD coating hydrophilic base paper changed to hydrophobic one, as proved by water contact angle (WCA) measurements. The water vapor transmission rate (WVTR) of base paper decreased sharply from 543 g/m 2 ·day to 2 g/m 2 ·day in the case of PVA/AKD triple coating, where the threshold of WVTR was reached. Meanwhile, the pristinely non-grease resistant base paper converted to a product with the highest grease resistance level. Furthermore, both elongation at break and tensile strength of base paper improved markedly after PVA/AKD coating. It was concluded that these improved properties were contributed by the combined use of PVA and AKD in the coating.

The inorganic core-shell pigment CaCO3{\mathrm{CaCO}_{3}}@SiO2{\mathrm{SiO}_{2}} was synthesized using a sol-gel method, and the pigment was applied as a surface coating on inkjet paper to study the influence of inorganic core-shell pigments on the dynamic permeability, surface properties, optical properties and inkjet-printing performance of coated paper. CaCO3{\mathrm{CaCO}_{3}}@SiO2{\mathrm{SiO}_{2}} prepared using carboxymethyl cellulose (CMC) had better coverage than that prepared using polystyrene sodium sulfate (PSS) dispersant. The CMC-prepared CaCO3{\mathrm{CaCO}_{3}}@SiO2{\mathrm{SiO}_{2}}-a had improved dispersibility, and the solids content of the coating reached 35 %. Inorganic core-shell pigments improve the surface and optical properties of the coated paper, making them similar to those of a reference calcium carbonate-coated paper. The smoothness and gloss improved by 60.8 % and 78.4 %, respectively, compared with those of silica-coated paper. The inkjet solid density and dot definition increased by 28.8 % and 4.1 %, respectively, compared with those of the calcium carbonate-coated paper. Preparing inorganic core-shell pigment CaCO3{\mathrm{CaCO}_{3}}@SiO2{\mathrm{SiO}_{2}} is an effective method to fabricate inkjet printing coatings with advantageous microstructures for ink absorption.

The ultimate goal of each production process is to optimize all the subprocesses leading to the high quality final product. Within the printing process, dot gain is identified as one of the most important variables to control because of the extremely negative impact to middle tone contrast and the overall reproduction. Dot gain consists of two components, mechanical and optical dot gain, as a result of two different contributions. This article proposes a model for separately analyzing components of dot gain for electrophotography prints using gradient method, where the impact of printing technique and paper type will be examined. It is shown that mechanical dot gain for electrophotography prints can be satisfactorily approximated with Gaussian, whilst optical dot gain is once again confirmed to have the form of a Lorentzian.

Paper has a crucial impact on the qualitative properties of printed product as properties of the paper’s surface directly impact the ink transfer, consequently, basic optical properties of the print. Although same ISO paper type, papers possess variable surface properties leading to different influence on the ink transfer. The aim of this research was to analyse influence of the surface properties of the paper, including surface free energy, smoothness and gloss of some standard papers used in lithography on the ink transfer while matching the colorimetric values defined by ISO 12647-2:2013. Determination of amount of the ink transfer, optical density, mottling and colour difference of prints were performed to evaluate paper-ink interactions. Results have shown that produced prints differ in the investigated properties. Furthermore, there are significant correlations between the surface free energy of the paper and paper smoothness and the ink transfer. In addition, amount of ink used to produce a standardized print varies for different paper types (even in the same ISO paper classification), meaning difference in ink costs. This research proved the high influence of paper’s certain parameters on the ink transfer by strong correlation coefficients. This enables better process control and optimization of the printing.

During recent decades the quality of pulp and paper mill sludge has changed. This has awakened the need for an applicable means to observe the sludge dewatering process diversely and accurately. To maximize the solids content and energy efficiency of board mill sludge dewatering, different process monitoring options were studied. Novel methods for monitoring the sludge dewatering operation of a belt filter were tested. Continuous run-time measurements and test response experiments were carried out at a board mill site. IR transmittance measurement through the filter web and sludge mat thickness measurement using a light curtain turned out to be very promising techniques. IR transmittance responded to the polymer content of the sludge without a notable time lag, while the solid content measurement of the filtrate did not give a measurable response.

The pretreatment using solid alkali had a high delignification rate and could improve the followed conversion efficiency of the biomass. In the present work, the bagasse lignin was separated and pretreated using a solid alkali to discuss their structural changes. The results showed that the main basic structures S/S′/S′′, G/G′, and H had different reactivity, where only the H unit was a stable structure in the pretreatment. The phenolic structure of the lignin was easily degraded in the pretreatment, and the lignin without phenolic structure was difficult to be degraded. The P structure was a novel structure that generated in the pretreatment. Some monomeric aromatic compounds simulated lignin monomer were also pretreated by solid alkali, the result showed that the phenol structure with side chain on para-position, as well as the carboxyl group, eater linkage, and double bond on the side chain are easily reacted in the pretreatment.