Surface Fracture
The formation of networks of microscopic hairline cracks within polymer or varnish coatings on paperboard occurs during folding and converting operations. This structural defect known as micro crazing appears when the coated board is bent around sharp corners, stretching the outer coating layer beyond its elastic limit. Although the paperboard substrate remains intact, the protective surface coating develops fine splits that are invisible to the naked eye under standard factory lighting.
This localized material failure occurs most often during high-speed folding in packaging carton assembly. It diminishes the appearance and performance of high-end boxes.
Barrier Degradation
Cracks in the protective barrier destroy the resistance of the packaging to moisture and grease. When micro crazing occurs, the barrier property is compromised because liquids can bypass the coating and penetrate the porous paperboard underneath. This causes rapid deterioration of the paperboard structure and spoils the packaged food.
Testing with colored dye solutions reveals these crack patterns.
Elastic Formulation
Formulating coatings with higher elasticity and plasticizer content prevents the cracking of the protective layer. To eliminate micro crazing, chemical engineers adjust the polymer blend to increase flexibility during folding. Flexible polymers can deform without breaking when stretched over board corners.
This formulation change preserves the integrity of the barrier during carton folding.
