Optical brightening agents (OBA) or fluorescent whitening agents (FWA) are commonly used in the paper industry to improve the optical performance of paper products. The increased use of bleached chemi-thermo-mechanical pulp (BCTMP) or high-yield pulp (HYP) in printing and writing paper grades has initiated research topics on the brightening efficiency of OBA on mechanical pulp-containing furnishes. In this study, process parameters that may affect the retention of OBA were investigated, such as furnish composition, OBA charge, contacting time, water hardness, anionic trash, and fines in HYP. It was found that OBA had lower retention on HYP fibers than on bleached kraft pulp (BKP) fibers. Efforts were also made to understand the underlying mechanism.

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Although high-yield pulps (HYP) are gaining increasing use to replace hardwood kraft pulp in paper grades such as uncoated and coated fine papers, the amount has been typically limited to less than 20% because there are concerns about its potential impact on papermaking operation and product quality. To address these concerns, laboratory experiments that mimic the actual paper machine operation were carried out and coated paper samples from mill trials were examined to clarify the impact of high-level HYP substitution on the properties of coated wood-free papers. Results showed that the HYP substitution, even at 40%, did not yield negative effects on strength properties such as tensile and tear; in fact the Scott bond increased with the HYP addition. The small increase in the surface roughness from the HYP addition can be eliminated by the filler addition, precalendering, and coating process. The lower brightness and CIE (Commission Internationale d'Eclairage) whiteness of the HYP can be compensated for by the addition of optical brightening agents (OBAs) and dyes, as well as pigments in the coating color. The analysis of samples collected from mill trials indicated that coated paper containing 40% HYP has lower coating penetration than that containing 40% HYP content paper samples. This was attributed to the smaller pore size created by HYP substitution. No significant differences were found between the samples containing 17 and 40% HYP on print gloss, color gamut, and print gloss uniformity. The implication from this study is that the HYP substitution level can be increased up to 40% in the production of coated wood-free paper without significant negative effect on the paper quality.

Hot deformation experiments of as-cast 35CrMoV steel, with strain rates of 0.01 s−1 and 10 s−1, deformation temperatures of 850, 950, and 1050 °C, and an extreme deformation reaching 50%, were carried out using a Gleeble-3810 thermal simulator. Electrochemical corrosion experiments were conducted on the deformed specimens. The microstructure was observed by optical microscope (OM), and the corrosion morphology and corrosion products of the specimens were investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), confocal laser scanning microscopy (CLSM), and X-ray diffraction (XRD) techniques. The results show that the grain size increased gradually with an increase in the deformation temperature at the same strain rate, whereas the corrosion resistance deteriorated. At the same deformation temperature, the grain size becomes smaller as the strain rate increases, which enhances the corrosion resistance. This is mainly attributed to the fine grains, which can form more grain boundaries, increase the grain boundary area, and accelerate the formation of the inner rust layer at the beginning of corrosion. Moreover, fine grains can also refine the rust particles and enhance the bonding strength between the inner rust layer and the matrix. The denseness and stability of the inner rust layer increases as the corrosion process progresses, thereby improving corrosion resistance.

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