Caps and closures is one of the largest and most complex packaging market segments. Plastic closures are widely used for containers and packages for beverages, foods, cosmetics, chemicals and pharmaceuticals. Closures protect the contents and seal the container to maintain shelf life and keep products secure from undesired opening. Such a wide range of applications requires many types of closures, such as screw top, tamper-evident, dispensing, hinge and snap-on.
Polypropylene and polyethylene are the two major polymers used for plastic caps and closures, which are manufactured through injection molding (IM) or continuous compression molding (CCM) processes. Depending on the end use, a plastic cap or closure may require a balance of characteristics, such as stiffness, toughness, deformation resistance, environmental stress cracking resistance (ESCR), taste and odor performance, seal performance, dimensional stability and torque removal (openability).