The Blister Packaging Properties Of Coated White Cardboard And Its Peeling Strength

As a new technique developed in the1980s, vacuum blister package not only boasts of fewermaterial costs, light weight, high barrier and environmental friendliness but also guaranteesthe interior products readily visible, therefore contributory to its widespread use amongelectronic products or small commodities. Hence, coated white cardboard, the most popularpackaging material in blister package, also witnesses increasing extensive applications.Since packaging process is always completed by clients that load in the products and adherethe blister pack to the cardboard due to mere provision of blister paper by package printingenterprises manufacturing paper blister packages, quality concern most common to blisterpaper is poor seal. In light of the criteria for qualified paper blister packages that over2/3contact paper surface are torn apart while peeling the blister packs, effect of blisterpredominantly depends on the property of coated white cardboard when such conditions astemperature, pressure, blister varnish and blister packs remain consistent.In blister packaging practices, blister outcomes were greatly anchored to the permeationdepth into coated paper by blister varnish and the surface strength of the coating and thesetwo properties in turn were impacted by the coating structure at the paper surface. Thereby,this paper, proceeding from a quantitative representation of permeation depth of blistervarnish under laser scanning confocal microscope (CLSM) and with added fluorochromeRhodamine B as the tracer, aimed to study the impact of coating material and process onpaper surface property and blister varnish permeation, and ultimately the impact on blisterpackaging. In the meantime, this paper was committed to the establishment of a predicativemodel on blister peeling strength through analysis about the relationship between paperproperty and blister peeling, which could in combination with visual evaluation predict blisteroutcomes of the paper prior to printing so as to minimize poor blister and save costs.Since calcium carbonate particles were found with obviously smaller median particlesize than kaolin in laboratories, calcium carbonate coating was unveiled more closely attachedin dye particles, smooth in surface, lower in porosity and shallow in permeation depth ofblister varnish but manifested with the highest surface strength that resulted in more powerfulblister peeling strength. Increases of adhesive dosage could lead to remarkable decreases ofpaper surface porosity and blister varnish permeation depth but proved capable of enhancingsurface strength and blister peeling strength. Higher coating solid contents and dryingtemperature could attenuate surface roughness, porosity and blister varnish permeation depth of the coating paper but could upgrade surface strength and maximize the single factor changeof blister peeling strength when the solid content was kept at50%and drying temperature at110℃. Calendering exerted significant changes on paper surface properties which wasdisclosed to remarkably tone down paper roughness, surface porosity, ink sorption and blistervarnish permeation but distinctly drive up surface strength and blister peeling strength.Besides, increasingly thick blister coating prompted initially extensions of actualpermeability depth inside the paper but then fluctuate at a higher level, which simultaneouslycould induce similar changes of blister peeling strength. Under the circumstance of the sametype of diluent, greater dosage could increase blister varnish permeation depth and augmentblister peeling strength. Nevertheless, more extensive printing screen dots or thicker printingink layers were found to obstruct permeation of blister oil into the paper and render an overalldecrease tendency of blister peeling strength.Moreover, blister packaging outcome was greatly confined by the paper surface strength.Surface strength which is mainly used for evaluation of the fiber’s bonding capacity, can notdeliver a completely faithful reflection of linting and dusting tendency. With the samemanufacturing materials and conditions, mere augmentation of the water content in finishedpaper or paper compactness or paper interlayer bonding strength within reasonable rangescould elicit corresponding increases of paper surface strength, with paper manufactured fromwood pulp higher than that from bamboo pulp or grass pulp. Increased ratio of mediumfiber to long fiber in the pulp and decreased quantity of fiber fines and long fiber wererevealed able to distinctly improve paper surface strength. In addition, the loose contents atthe paper surface offered a direct telling of linting and dusting degree, indicating that the moreloose contents at the paper surface, the lower the surface strength.Overall, the surface roughness, ink sorption, surface strength and blister varnishpermeation depth of the coating paper are unveiled in linear correlations with blister peelingstrength and moreover, the multiplication of the surface strength by peeling strength in betterlinear correlation with blister peeling strength. Predicative model on blister peeling strengthY=2.931X1-0.014X2+0.728X3-2.609is verified with about5%error margin between itscalculation values and actual measurement values, suggestive of some feasibility.Additionally, the model combined with visual observation about peeled paper layers andpeeling consistency could assess blister packaging effect of the paper in a comprehensivemanner.In addition, sealed in surface, extremely poor in ink sorption and relatively low insurface tension, vacuum aluminum-plating paper is demonstrated hard for blister varnish to attach at the surface and to permeate inside, so the multiple layers of paper can not be adheredand only the blister oil layer is stripped at peeling. Therefore, effective blister packaging cannot be materialized, which suggests it of ultra-low blister peeling strength. Consequently,vacuum aluminum-plating paper is not applicable in blister packing industry.