纸的匀度

Evenness of paper sheet

纸张匀度属结构性品质,影响纸张多种性能。本文描述了纸张匀度的精确定义和从目测、到用光学仪器、再到用β射线不断改进的检测方法。理论与实践相结合地阐明了影响匀度的主要因素,即纤维本性、浆料的絮聚(包括浓度)、湍动、浆网速比产生的剪切力和湍动,并从流浆箱的动能和成形器里形成网络的过程来加深对匀度的理解。显示出了不同种类和结构的成形器经优化后所能达到的匀度水平和匀度与印刷均一性的线性关系,提出了在生产建设中优化和改进匀度的途径。

Evenness, as a structural feature, influences various performances of paper. This article elaborates the precise definition of paperevenness and the testing methods improved from visual range estimation to the use of optical instrument and then further to the application ofβ- ray. It puts forward through both theory and practice that the major factors contributive to paper evenness are fiber nature, flocculation(including concentration), shear force and turbulence. The kinetic energy of the headbox and the web formation process in the former areintroduced for enhanced understanding of paper evenness. Levels of evenness achieved by the improved formers of various types and construc-tions are presented as well as the homogeneous linear relationship between evenness and printing. Approaches for evenness optimization andmodification are also suggested.