Dispersion Barrier Performance in Folding Boxboard Substrates
Aqueous dispersion barrier performance depends on wet coat weight uniformity, film drying coalescence, and creasing matrix geometry that prevents score line cracking.
Polymer Strain at Break
Deformation Property
The maximum elongation a polymer film can withstand before rupturing provides a measure of its flexibility and toughness. Polymer strain at break is expressed as a percentage of the original length and determines how well a coating handles mechanical stress. This value is critical for materials that must survive the creasing and folding of a carton.
It reflects the internal cohesion and molecular weight of the resin.
Testing Variable
Tensile testing machines pull a free film of the material at a controlled rate until it fails. The polymer strain at break value varies with temperature and humidity, as these factors influence the mobility of the molecular chains. A higher percentage suggests a more rubbery and resilient material suitable for deep drawing or complex folds.
Converting Influence
Coatings with a low value for this property tend to crack at the corners of a box, exposing the underlying paper fibres. A high polymer strain at break ensures that the barrier remains continuous even when the substrate is stretched or compressed. This prevents the loss of grease resistance or moisture protection at the points of highest physical distortion.
Matching the elasticity of the coating to the requirements of the folding geometry prevents functional failure in the field. Finished packages retain their aesthetic appeal because the coating stays intact during the forming and filling process.