Fracture Toughness, Measurement, and Applications Related to Paper Break

Résumé fourni par la source

Paper break is important in enhancing the runnability of papermaking, converting, and printing processes and contributes toward reducing production costs. According to published research, traditional tensile, tear, and burst strengths are not closely related to paper break, because it occurs at a failure strain of around 20–30%. However, fracture mechanics (FM) and fracture toughness are closely related to paper break. FM can be divided into linear-elastic FM (LEFM), nonlinear FM (NLFM), and elastic plastic FM (EPFM), however, LEFM is not relevant to paper, as it undergoes significant plastic deformation in front of a crack tip. NLFM and J-integral analysis are recognized as applicable theories with which to analyze paper break, where the J-integral is the resistance to crack extension of a material. KS M ISO 17958 was established after synchronization to ISO standards showed how to measure the fracture toughness J-integral values of paper and board. It has shown that strategies including more refining, stronger intrinsic fiber strength, fewer shives, lower calender pressure, better formation, greater thickness, stable wet-end operation, less fluttering, higher moisture content, and higher temperatures are beneficial for reducing paper break. It is known that the wet web strength of the operating side and drive side of the paper width are more critical to paper break than other regions. The current FM theory cannot be used to completely understand paper break, so an understanding of the dynamics of paper break must be pursued.

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