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Amphoteric polyacrylamide (AmPAM) is a linear water-soluble polymer that has been applied in papermaking as an agent for flocculation, retention, filtration, and dry-strength improvement. However, AmPAM with different ranges of molecular weight (MW) have different properties in these processes. In this study, a series of AmPAMs were constructed with an anionic monomer, itaconic acid (IA), a cationic monomer, methacryloxyethyl-trimethyl ammonium chloride (DMC), and a main backbone of acrylamide (AM). Four factors influencing free radical polymerization, i.e., reaction temperature, pH, initiator load, and the concentration of monomers, were systematically investigated via an orthogonal test to determine their effects on the MW of AmPAM. Spectroscopy and isoelectric point assays were used to characterize the structure of the produced AmPAM, and the MW was assessed by calculating the viscosity. The reaction temperature had the greatest influence on the MW of AmPAM, followed by the solution pH and the initiator load. To determine the dry strength of papersheets containing AmPAM, the breaking length of handsheets was assessed after adding 0.5% AmPAM (based on fiber) with different MWs. The maximum value, 4.05 km, was 15.0% higher than the control and was obtained using AmPAM with a MW of 330 kDa. [ABSTRACT FROM AUTHOR]

Corncob, an underutilized agricultural byproduct, was used as the raw material to make a dry-strength additive for paper. Corncob was ground into 80, 100, 150, and 200 mesh powder. The powder was treated with sodium chlorite to remove lignin, and the resulting holocellulose was modified with hydrogen peroxide. The influences of oxidation time, concentration of hydrogen peroxide, dosage of paper strength agent, and the dosage of aluminum sulfate on the paper properties were studied. The results indicate that the oxidized corncobs holocellulose can improve the tensile index, burst index, and folding endurance of paper. Compared with control paper, when the concentration of hydrogen peroxide was 0.9%, the tensile index, burst index, and folding endurance were increased by 24.2%, 14.1%, and 463.8%, respectively. The particle size of raw material, dosage of strengthening agent or aluminum sulfate greatly influences paper properties. Scanning electron microscopy (SEM) analysis showed that the combination between the fibers was improved after adding the strengthening agent, thus improving the strength of the paper. The results can provide a new method for value-added use of corncob. [ABSTRACT FROM AUTHOR]

new net-cationic polyacrylamide dry strength agent was synthesized through free radical polymerization using acrylamide (AM), itaconic acid (IA), N,N-dimethylacrylamide (F), and sodium methallyl sulfonate (T). Ethylene diamine tetraacetic acid was used as a chelating agent; dimethylaminoethyl methacrylate methyl chloride (DMC) solution was used as a cationic monomer, and ammonium persulfate (APS) was used as an initiator. Orthogonal design and single-factor experiments were utilized to study the effect of many factors, such as reaction time, the ratio of monomers, and the dosage of APS and DMC on the cationic polyacrylamide. The synthesized products were characterized by Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), particle charge detector (PCD), and zeta potential analysis. The results showed that the optimum conditions were as follows: optimal monomer proportion: m(AM):m(IA):m(T):m(F) = 23.79:2.39:0.21:0.32; w (DMC) = 28%; w (APS) = 1.0%, reaction time was 3 hours, reaction temperature was 93 oC, stirring speed was 130 rpm, and reaction pH value was 3.0. The solid content of the polymer was 21.2%. By adding the cationic polyacrylamide to old corrugated container pulp, the tensile index increased by 29.7% and the burst index increased by 66.1%, displaying the obvious enhancement of the paper. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to evaluate the ability of molasses, a low cost by-product of the sugarcane extraction, for improvement of the physicomechanical properties of old corrugated container (OCC) recycled paper as a dry-strength agent. The influence of fiber beating on the enhancing effect of molasses was also investigated. Five dosages (0%, 5%, 10%, 15%, and 18%) of molasses and 3 levels of freeness (420, 400, and 320mL CFS) were used as variable factors. For each treatment, 6 handsheets, each having an area of 200cm2 and basis weight of 120g/m2, were made. The experimental results showed that except for the case of tear index, the increase in mechanical and physical properties were considerably higher than control (untreated) samples. Significant changes of tensile and burst indices, breaking length, and air resistance were observed after the addition of 18% molasses. From a statistical viewpoint, the addition of molasses had more positive effects on the above-mentioned properties, compared to the fiber beating. However, at a certain dosage of molasses, with increased beating, the strength properties were improved remarkably. This is due to the molasses adsorption efficiency, which depends on the specific surface of particles. The water retention values (WRV) were moderately increased by applying molasses, however with increasing dosage the WRV was improved. From these findings, it is concluded that molasses is a promising dry-strength agent and it can also be used as a replacement for cellulosic fibers. This conclusion is in good agreement with the previous research articles, which introduced molasses as a new additive in papermaking. [Copyright &y& Elsevier]

Cationized birch xylan was prepared and its use as a papermaking chemical was evaluated. The focus was on studying the effects of cationized birch xylan on the wet and dry strength of fine paper. The results of the laboratory experiments show that the addition of 3 percent of cationized birch xylan to birch kraft pulp improved the initial wet strength of the web by 30 percent compared to base stock at a solids content of 55%. Furthermore, the tensile stiffness of the wet web increased by approximately a third and the dry tensile strength improved by 26%, while the dry elastic modulus was not changed. The improvements in the strength properties were clear when compared to the base stock, but not as high as achieved with conventionally used cationized starch. The difference between the xylan and starch is most likely due to the shorter polymer chain length of the cationized xylan. [ABSTRACT FROM AUTHOR]

Surprisingly the strength of wet paper is still poorly understood. Here we show that the traditional explanation of the strength of wet paper is incorrect. Observations that the capillary force in fiber crossings in wet paper approaches zero as the water is evaporated show that they are not responsible for the strength of wet paper. Instead we present evidence that fiber entanglements and friction are the cause. Like paper, films made of nanotubes, nanorods, nanofibers or nanoribbons also consist of randomly oriented fibers, and this field may well benefit from an increased knowledge of paper properties. [ABSTRACT FROM AUTHOR]

Corrections to the article "Wrinkling of a Stretched Thin Sheet" that was published in the 2011 issue is presented.