Study On The Change Of Pulp Properties During Wet-heat Aging And Deacidification Of Aged Paper

Paper plays an irreplaceable role in the human civilization,but the properties of paper alter as the change of environmental conditions during application of paper.A large number of paper has been destroyed.The protection of paper is a problem we urgently need to solve.In this thesis,the thermal performance of pulp and the mechanism with aging are systematically studied aiming to provide theoretical support for a series of problems such as the decrease in strength with aging,the deacidification and strengthen of paper.Tensile index,tear index,brightness,degree of polymerization,pH value of paper during the aging process are investigated in detail.As the increase of aging time,they present a downward trend.The degree of polymerization of cellulose has a great influence on the strength properties of paper.When the degree of polymerization of aging paper is high,some polymers can be added to enhance the binding force between fibers to strengthen.When the degree of polymerization of aged is low,the paper can be reinforced by film formation.There is a quantitative relationship between pH value and carboxyl content.The content of carboxyl groups can be estimated by determining the kind of pulp and pH valueThe strength properties such as tensile index and tear index of softwood pulp and hardwood pulp with different beating degrees present a downward trend as the increase of aging time.The analysis shows that the fiber length of the pulp remains basically the same during the aging process,so the decline in the strength properties of the pulp is not due to the shortening of the fiber;For softwood pulp,the higher the beating degree,the greater the decrease rate of tensile index and tear index;For hardwood pulp,with the increase of the beating degree,the decrease rate of tensile index is slightly higher,the tear index is slightly lower,indicating that the beating treatment of pulp can accelerate the aging of ancient books The beating treatment of pulp has almost no effect on pH value and crystallinity of pulp during aging for softwood and hardwood.The beating treatment has a greater influence on the degree of polymerization of softwood pulp and less on the degree of polymerization of hardwood pulpThe nanoparticles of Mg(OH)2 modified by oleic acid were uniformly dispersed in hexamethyldisiloxane to form a stable deacidificanon liquid,which was sprayed on the aged paper to realize deacidification of the paper,It was observed that the modified Mg(OH)2was prepared when 0.1 g of oleic acid treated with 1g of nanometer Mg(OH)2 at 50℃ for 1 h,the modified Mg(OH)2 could well dispered and could be used for deacidification of paper.1 g of oleic acid-modified Mg(OH)2 nanoparticles dispersed in 1L of hexamethyldisiloxane was used as deacidfication liquid.When the deacidification liquid spraying amount was 2.7 g/m2,the pH value of the paper surface significantly improved(from 4.00 to about 7.92),The heat aging test indicated that the papers after deacdfication showed a good stability of pH value(about 7.60)the tensile index and tear index declined slightly but far later than that of undeacdified ones and the chromatic aberration was 4.64.The appearances of the paper before and after deacidificatian had little difference.