GCM 240 Chapter Notes - Chapter 4: Ultimate Tensile Strength
30 Sep 2016
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Grain: results from fiber alignment during formation of sheet: fibers tend to align themselves parallel to the machine direction. Grain long paper: grain runs parallel to long dimension of press sheet. Grain short paper: grain runs parallel to short dimension of sheet. Paper tears and folds easier in the grain direction. Paper experiences greater stiffness and tensile strength in the grain direction. Paper expands or contracts more in cross direction than in grain direction with changes in moisture content. In binding, grain parallel to binding edge of book is preferred. Curl/wet/flotation test: sample square paper is cut from a paper, sheet placed in water, label sides of the square sample with le and se, the grain direction will be parallel to the curl. Wire side: open structure, less sizing and filer. The weight of paper relative to its volume. Denser paper is compact with their fibers more tightly bonded.
