Document Type : Complete scientific research article
Authors
1
Associate Professor, Department of Wood and Paper, Savadkouh Branch, Islamic Azad University, Savadkouh, Iran
2
Assistant Professor, Department of Engineering Sciences, National University of Maharat, Tehran, Iran
Abstract
Background and Objective:
Writing and printing paper, due to its characteristics such as whiteness, gloss, air resistance, and favorable printability, is regarded as one of the main types of paper used in the printing industry. However, domestically produced samples still require improvement in terms of colour uniformity, surface roughness, and physical properties—factors that can significantly influence print quality. In this study, to enhance the physical and printing properties of the writing and printing paper produced by Mazandaran Wood and Paper Company, biodegradable coating materials including nanographene, zein, and fluorine were employed.
Materials and Methods:
For this purpose, writing and printing paper with a grammage of 70 g.m-2 was prepared and subjected to various tests. To coat the paper surface, nanographene, zein, and fluorine were weighed separately, along with styrene-butadiene latex at specified weight percentages. Based on the treatment conditions. The materials were mixed in a blender at a rotational speed of 1500 rpm for 20 minutes to obtain a homogeneous mixture. This process ensured the uniform distribution of materials on the paper surface. Before conducting the tests, both control samples and coated samples were placed in standard environmental conditions (20°C and 65% relative humidity). The characteristics examined in this study included thickness, ash content, air permeability, roughness, opacity, whiteness, brightness, gloss, optical density, and adhesion. These characteristics were measured accurately to thoroughly assess the impact of coating on paper quality.
Results:
The results indicated that coating increased thickness, ash content, air permeability, whiteness, gloss, and optical density. Compared to the control sample, these features showed significant improvement. However, a decrease in opacity and brightness was observed, indicating that the coating positively affected the visual quality of the paper. In cases where coating materials were used separately, roughness also decreased, which in turn could affect print quality. In other words, the air resistance of the sample coated with graphene, zein, and fluorine increased by approximately 35 times compared with the control sample. Moreover, the ash content in the zein-coated sample was about 5.96 times lower than that of the control, indicating an improvement in paper quality. The opacity of the fluorine-coated sample showed a 3.7% decrease compared to the control. Additionally, the zein-coated sample exhibited a 45.5% increase in whiteness, while the sample coated with both zein and nanographene demonstrated a 431% increase in gloss. The adhesion of the coated layer and the applied flexo ink was excellent, as both layers were completely removed along with the paper surface (substrate) by the adhesive. This feature indicates the high ability of this type of coating to maintain cohesion and print quality.
Conclusion:
This study demonstrates that the use of nanographene, zein, and fluorine as coatings can significantly improve the physical and printability features of writing paper. In particular, the increased gloss, whiteness, and air permeability make this paper a more suitable option for book printing. Overall, these results can contribute to the design and production of high-quality papers and add greater value to the printing and paper industry in Iran.
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