فهرست مطالب m. mohammadi achachluei

Paper turns yellow over time. Bleaching with oxidizing agents is one of the most common methods, which creates a colorless result by breaking down the light-absorbing chromophores. In this research, the changes in the properties of paper by applying oxidizing agents are studied. The paper samples were characterized by colorimetric, infrared spectroscopy, tensile, acidity, and SEM microscopes. Four oxidizing solutions were deployed for whitening the samples of Whatman paper using the Immersion method, including Hydrogen Peroxide (2 % V/V), Sodium Peroxide (2 % W/V), Potassium Periodate (2 % W/V), and Potassium Persulphate (2 % W/V) all solved in distilled water. The samples were treated within 48 hours, and characterizing tests were deployed. The results show that hydrogen peroxide with the highest tensile strength (17.75 Nm/g) and the lowest color difference (∆E= 1.48) after accelerated aging has the best performance among other samples. Also, hydrogen peroxide can be improved tensile strength, increase brightness, reduce yellowing, cause fibers stability, and keep the paper at an almost neutral acidity.

Various destructive factors gradually degrade paper due to its structural properties. For this reason, it is necessary to apply consolidation treatments for strengthening the degraded papers. In this study, cellulose nanofibers with a concentrate of 1% by weight were prepared as a suspension with water to consolidate the paper, then used to treat the samples. The samples were exposed to dry-heat and moist-heat aging to evaluate the treatment effects. pH measuring, colorimetric, and tensile strength tests were performed before and after aging. The results showed that the pH of the cellulose nanofibers treated samples increased. After dry-heat and moist-heat aging, the pH of the samples decreased slightly. Cellulose nanofiber treatment increased the tensile strength of the samples. However, after two stages of aging, the tensile strength of the samples has reduced compared to the previous stage. The application of cellulose nanofiber treatment made the color of the samples brighter, but after aging, the brightness of the samples decreased.