Abstract
Abstract The crack area on a coated board was measured after creasing and folding and the crack area on a coated copy paper was measured after folding. A clay pigment and two Ground Calcium Carbonate (GCC) pigments were used. The GCC pigments differed in their particle size distribution. The binder was either an S/B Iatex or an S/B Iatex combined with starch. The type of pigment seemed to have the greatest intluence on the crack area in creased and folded board. Clay showed a !arger crack area than the GCC with a broad particle size distribution. The GCC with a narrow particle size distribution showed a considerably larger crack area than both the clay pigment and the GCC with a broad particle size distribution. The coatings containing starch generally showed a larger crack area than the coatings that only contained the S/8 latex. After the folding of the copy paper, the crack area showed a slightly different pattem. Here, it seemed that the binder was of greater irnportance than the type of pigment, with the coatings containing only latex showing a considerably lower crack area than the coatings containing starch. The coatings that were based on the clay pigment showed similar values as the coatings based on the GCC pigment with the broad particle size distribution. The coatings based on the GCC with the narrow particle size distribution showed displayed considerably higher crack areas than the coatings based on the other two pigments. The cracking tendency of the coatings, based on the GCC with the narrow particle size distributions was probably due to a greater demand for latex, i.e. smaller particles in the GCC with broad particle size distribution would probably fill in the voids and the GCC with the broad particle size distribution will therefore demand less binder. lt was further suggested that the different loadings on the coating layer during the creasing and folding of the board, compared to the folding of copy paper, explain the different results obtained with the two base-substrates.
Published Version
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