Effect of gamma-irradiation on the strength properties of paperboards and corrugated fiberboards with different grades and effect of recycling on the irradiated sheets

Effect of gamma-irradiation on the strength properties of various paperboards and corrugated fiberboards with different grades and effect of recycling on those irradiated sheets were investigated. Results obtained are summarized as follows: 1) Postradiational changes in the strength properties of AA-, A- and C-grade linerboards showed approximately same tendency. 2) After 25kGy irradiation (usual sterilizing dosage), AA- and A-grade linerboards reduced the ranking to A- and B-grade respectively, however, C-grade liner and A-grade medium remained in each grade. 3) Corrugated fiberboard composed of AA-liner and A-medium remained the rank of S-4 (JIS Z 1516) even after 25 kGy irradiation. Corrugated fiberboard composed of A-liner and A-medium also remained the rank of S-3 after 25 kGy irradiation. 4) Canadian standard freeness of recycled stock from the irradiated samples decreased with increasing dosage, and the increase of short fiber fractions by the irradiation was observed. 5) The strength properties of handsheets recycled from the irradiated samples were lower than those from unirradiated samples except the wet tensile strength. Lowering degree of the strength properties was given in the following order: Folding endurance>Tearing> Bursting>Dry tensile. (author)