环境相对湿度对纸张破损风险的影响

Effect of Ambient Relative Humidity on Damage Risk of Paper

关键词:  环境相对湿度  纸张  破损风险  耐折  撕裂

Key Words:ambient relative humidity  paper  damage risk  folding  tearing

摘要:本研究通过测量不同环境相对湿度下，纸张的抗张指数、耐折度和撕裂指数，考察了环境相对湿度对纸张机械强度的影响；然后分别采用机械强度降幅法、机械强度和纤维素聚合度（DP）关联法评估环境相对湿度偏低（15%）和偏高（85%）对纸张破损风险的影响。结果表明，环境相对湿度偏低时，纸张的撕裂指数下降；环境相对湿度偏高时，纸张的抗张指数下降；环境相对湿度偏低或偏高时，均有部分纸张耐折度下降。由联用机械强度降幅法及机械强度和DP关联法可知，打字纸和老化打字纸本身撕裂指数中等或较低，当环境相对湿度偏低时，撕裂指数进一步下降，撕裂风险提高；老化字典纸和老化新闻纸的撕裂指数虽然在环境相对湿度偏低时降幅超过20%，但撕裂指数仍较高，撕裂风险不会显著提高；其余纸张的撕裂指数在环境相对湿度偏低时降幅较小，撕裂风险无显著提高。环境相对湿度偏低或偏高时，只有老化道林纸耐折度降幅大于20%，但也未达到显著影响折断风险的阈值，折断风险不会显著提高。环境相对湿度偏高时，所有纸张的拉断风险提高。因此，环境相对湿度偏低时对机械强度较好纸张的破损风险无明显影响，但会增加机械强度较差纸张的撕裂风险或折断风险，环境相对湿度偏高会增加所有纸张的拉断风险。

Abstract:In this study， the effect of ambient relative humidity on the mechanical strength of paper were investigated by measuring the tensile index， folding resistance， and tearing index. Then， the mechanical strength reduction method and the mechanical strength and cellulase polymerization （DP） correlation method were used to evaluate the influence of the ambient relative humidity on the damage risk of paper. The results showed that the tearing index of paper decreased when the ambient humidity was lower（15%）. When the ambient humidity was higher（85%）， the tensile index of paper decreased. When the ambient relative humidity was lower or higher， the folding resistance of some papers decreased. According to the mechanical strength reduction method and the correlation method of mechanical strength and DP， the tearing index of type paper and aged type paper was small， and the tearing index further decreased when the ambient relative humidity was lower， so the tearing risk increased. Although the tearing index of aged bible paper and aged newsprint decreased by more than 20% when the ambient relative humidity was lower， the tearing index was still large， so the tearing risk would not be significantly increased. The tearing index of other paper decreased less when the ambient relative humidity was lower， and the tearing risk did not increased significantly. When the ambient relative humidity was lower or higher， only the reduction of folding resistance of aged glazed printing was greater than 20%， but it still didn’t reach the threshold of significantly affecting the folding risk， and the breaking risk will not be significantly increased. When the ambient relative humidity was higher， the risk of tensile failure of all paper was increased. Therefore， lower ambient relative humidity had no significant effect on the risk of damage of paper with good mechanical strength and may increase the risk of tearing or breaking of paper with poor mechanical strength， while higher ambient relative humidity increased the risk of tensile failure of all paper.