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A lignin-based PU coating was prepared for paper-based green packaging. Two representative diisocyanate were used to prepare the coatings. Due to the rigid aromatic, the physical properties of the TDI system reached the maximum below the lignin content of 40%. The HDI that contains flexible aliphatic chains alleviated the brittleness of coating, and it showed physical advantages when the lignin content was more than 50%. Owing to the high lignin content, the coating presented enhanced thermal stability. After coated with the lignin-based PU coatings, the dry tensile strength of coated paper was improved by 126%. Amazingly, the wet strength was increased from 0.31 to 12.6 MPa with an improvement nearly 40 times. Based on the coordination of lignin, Ag+ was introduced into the PU matrix, which imparted the coating with excellent antibacterial ability. The colony forming units of E. coli and S. aureus were both less than 1. However, no inhibition halo was observed, which indicated that the Ag was firmly anchored on the coating and the antibacterial ability is only available when the bacterial contact the coating surface. The lignin-based PU coating with favorable sustainability and properties shows great potential in paper-based green packaging fields. The prepared PU coating with high lignin content and firmly anchored Ag+ exhibits outstanding physical properties, thermal stability, and antibacterial property, which makes it an ideal candidate to be used in paper-based green packaging. [Display omitted] [ABSTRACT FROM AUTHOR]

Brittleness in paper is one of the primary reasons library books are removed from circulation, digitized, or have their access limited. Yet, paper brittleness is difficult to characterize as it has multiple definitions and no single measurable physical or chemical property associated with it. This study reevaluates the cantilever test as applied to aged papers. In this nondestructive test, the deflection of a strip of paper held horizontally is measured across its length. The deflection data are then fit to nonlinear bending theories assuming large deflection of a cantilever beam under a combined uniform and concentrated load. Fitting the shape of the deflection profiles provides bending and elastic moduli, the bending length, and confirms that the paper sheets respond linearly. The results are compared to those calculated from a simplified single point measurement of the maximum deflection of the cantilevered sample. Young's modulus measured by the cantilever test is lower for paper-based materials than that measured by tensile testing, and the bending modulus was found to correlate with the destructive Massachusetts Institute of Technology (MIT) fold endurance test. [ABSTRACT FROM AUTHOR]

: We analyze 6500 mm long fracture lines of paper as an example of crack propagation involving disorder. The cracks are asymptotically self-affine, with a roughness exponent close to 0.6. Systematic deviations from the power-law-scaling exist below a lengthscale related to the microscopic heterogeneities and possibly to a cross-over from 3d to 2d crack propagation. Several analysis methods are discussed, including first return analysis and the detection of correlated trends. [ABSTRACT FROM AUTHOR]