Secondary Amide Additives in Polyolefin Thermal Sealing Operations
Secondary amides eliminate seal jaw smoking and hot tack decay in polyolefin film sealing by maintaining low volatility at elevated operating temperatures.
Jaw Sticking
Meaning
Thermal adhesion of a thermoplastic film to the metal surface of sealing jaws leads to cosmetic blemishes and line stoppages during packaging operations. Preventative measures against jaw sticking focus on selecting the correct slip or release agents and controlling the temperature of the heat seal elements. This phenomenon occurs when the outer layer of the film reaches its melting point and fuses with the metal.
Thermal Limit
Exceeding the upper processing limit of the outer layer initiates polymer melting at the metal interface. High temperature exposure causes jaw sticking because the resin adheres to the bare tooling.
Surface Mitigation
Coating the metal jaws with fluoropolymer or utilizing high temperature release tapes prevents direct contact with the polymer. When jaw sticking occurs, these coatings act as a thermal barrier and reduce surface energy to facilitate clean release. Regular maintenance is necessary to prevent these sacrificial layers from wearing away.
Resin Formulation
Incorporating slip and anti-blocking additives into the film formulation alters the migration behavior and surface tension of the polymer. When slip agents are absent or have not migrated sufficiently, jaw sticking becomes a frequent cause of machine downtime. Adjusting the additive concentration or using more thermally stable agents allows processors to run at higher temperatures and faster cycle speeds without causing adhesion to the sealing equipment.