Paperboard Chemical Additive Retention and Migration Testing Methods
Paperboard chemical retention and migration compliance requires verifying wet-end additive fixation, simulant extractions, and mass transfer kinetic barriers.
Polyolefin Extrusion Coating
Melt Application
A converting process applies a molten layer of polyethylene or polypropylene to a moving web of paperboard. This technique involves melting polymer resin in an extruder and forcing it through a flat die to form a thin film on the paper. In paperboard manufacturing, polyolefin extrusion coating is the primary method used to add protective and heat-sealing functions to the board.
Moisture Barrier
The continuous polymer film created by polyolefin extrusion coating provides water and grease resistance to the fibrous substrate. This barrier layer is essential for packaging cold liquids, frozen foods, or moist bakery products that would otherwise soften untreated board. It also prevents grease from migrating outward from the food, keeping the outside of the carton free from stains.
Converting Quality
To ensure a strong bond, the paperboard surface is treated with corona discharge before the polymer is applied. This surface treatment improves adhesion by increasing the surface energy of the board, which prevents the polymer layer from peeling off during subsequent folding and sealing. Maintaining the correct melt temperature and line speed is also critical to ensure that the coating has a uniform thickness and remains free from defects.
This process control is monitored by regular tape-pull and thickness tests on the production line, ensuring that the final board behaves reliably on high-speed packaging machines.