Evaluation of the adhesion performance of latex-starch mixtures to calcium carbonate surfaces.

A number of studies have reported on the mechanical properties of paper coatings and the influence of various parameters on cracking at the fold. Failure at the pigment-binder interface is important to understand because it likely controls how coating layers fail or crack in different applications and processes. In this study, a model system of a calcium carbonate surface in contact with latex and starch binders was used to evaluate the interfacial bonding performance affecting failure in tensile mode. Samples of calcium carbonate marbles with binder films between them were tested in tensile tests and the results were compared with those of pure binder films. In addition, contact angles of calcium carbonate, latex and starch were measured. The failed surfaces were analyzed using Raman spectroscopy and scanning electron microscopy (SEM). All sample involving the calcium carbonate surface failed at a maximum stress of around 25% compared to that of pure films. Samples that contained starch exhibited larger maximum stress values than pure latex system. The strain at failure for these samples did not depend on the starch content to a large extent. While Raman results did not indicate any residual latex particles on the adhesively failed surfaces, SEM microscopy confirmed that at least part of the failure was still cohesive because regions of binder were present on the surface.