Abstract
The ability of adhesives to bond paper and paperboard is critical for most packaging and converting operations. Despite the huge body of literature describing both paper and adhesives technologies, there are only a few research papers describing paper/adhesive interactions. Described herein are the results of a systematic investigation of pressure sensitive adhesive (PSA) peeling from paper. The peel force versus peel distance curve depends upon the failure mode. A constant force is observed when the PSA cleanly separates from paper (i.e. interfacial failure) at low peel rate. By contrast, at high peeling rates, in the paper failure domain, the peel force climbs to a maximum and then relaxes to a steady-state value. The maximum peel force, which we call the peak force, corresponds to the fracture of the top layer of fibres during the initiation of paper delamination whereas the steady-state peel force occurs during the propagation of paper delamination.
To characterize the range of behaviors it is necessary to conduct a series of peeling experiments over an extended range of peel rates. The results are best analyzed by plotting the peak peel
force versus the peel rate on logarithmic axes giving what we call a peel map. For a broad range of tape/paper combinations, peel maps have similar shapes. The interfacial failure domain consists of a linear segment with a positive slope. This line intersects with a horizontal line segment at higher peel rates, corresponding to the paper failure domain.
Principal component analysis, a multivariate statistical analysis, of a large set of peel maps was used to reveal the influence of paper properties on peeling. The peak peel forces in the paper
failure domain correlated with standard paper properties linked to z-directional strength. The slopes of the peel maps in the interfacial domain were independent of paper properties but were sensitive to adhesive rheology. The absolute location of the interfacial segment of the peel map mainly was sensitive to the chemical composition of the paper surface and secondarily related to surface roughness. Water contact angles on paper were not good predictors of adhesion. Finally, we illustrate the utility of peak peel force in the paper failure domain as a measure of paper surface strength.
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