Fibre composition of packaging grade papers as determined by the Graff "C" staining test

Abstract

[EN] A qualitative and quantitative analysis of the fiber components of 15 representative papers that are used for the production of corrugated board was carried out by the Graff "C" staining test. The method of processing of softwood, hardwood, and nonwood fibers was determined under a light microscope by their color reactions with the stain. All papers, due to the use of recycled pulp raw materials in their manufacturing, were found to incorporate in their furnish fibers that had been produced with a variety of pulping processes: chemical, mechanical, and semi-mechanical. The recycled-based papers (recycled-liner and recycled-medium) were proved to be the most variable comprising 12-15 different fiber components, while in some of the semi-chemicals only up to 7 components were identified. The weight percentages of the fiber components calculated by the application of weight factors showed that in almost all papers the most important fiber component from a quantitative standpoint was hardwood unbleached kraft followed by softwood unbleached kraft. Besides hardwood unbleached serni-chemical pulp and mechanical softwood pulp that were also plentiful in the papers, there was a smaller number of other components which sum, however, accounted for a significant fraction in the total furnish weight. The results taken on the total softwood, hardwood, and nonwood fibers content of the papers demonstrate that Graff "C" staining test is adequate to analyze both the structure and quality of packaging grade papers in practical industrial testing.