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    In the area of photoyellowing of mechanical pulps, recently obtained experimental evidence has shown that hydroquinone/p-quinone redox couple is present in lignin-rich mechanical pulps. It was also noted that compared to a control pulp the concentration of p-quinones was significantly higher in a photoyellowed pulp. Under ambient conditions, upon exposure to light, the existent pulp hydroquinones were converted to p-quinones. To further investigate the importance of hydroquinone/p-quinone redox couple in photoyellowing, studies of methylhydroquinone and methyl-p-quinone were carried out. Based on presently reported as well as previously published research, it is shown that the hydroquinone/p-quinone redox system can successfully explain most of the observations related to photoyellowing. Consequently, the hydroquinone/ p-quinone redox couple plays a highly significant role in pulp photoyellowing.

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    Agarwal, Umesh P. 1999. On the importance of hydroquinone/p-quinone redox system in the photoyellowing of mechanical pulps. [10th International Symposium on Wood and Pulping Chemistry, Main Symposium, 1999 June 07-10, Yokohama, Japan]. Atlanta, GA : TAPPI Press, 1999.:p. 694-697 : ill.


    Hydroquinone, Benzoquinone, Mechanical pulping, Redox reactions, Photoyellowing, Yellowing

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