The influence of nanofibrillated cellulose (NFC) was investigated as a reinforcing agent to improve strength properties of papersheets fabricated from recycled pulp fibers of mixtures of old newspapers, old magazines, and old corrugated cardboards. This analysis further shows that the z-directional tensile strength is the best suited measure to determine the internal bond strength especially for high basis weight papers. On the other hand, the Scott bond energy is affected by basis weight and by the dynamic nature of the test which tends to over evaluate this parameter. In addition to the fiber-to-fiber bond breakage energy, the delamination energy includes the energy dissipated in the fibrous network of thick papers, while the z-directional tensile energy includes the energy of intrafiber bond failure especially for papers made from flexible chemical pulp fibers. The comparisons between these methods using the same unit of measure (J/m2) show that even though the results are highly correlated, these tests do not measure the same thing.
These are the z-directional tensile test, the delamination test, and the Scott bond test. Three methods are used to measure the internal bond strength of papers made from TMP, CTMP, and kraft pulps.
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