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.
Hot Tack
Meaning
Melted polymer seal strength measured immediately after the sealing cycle determines the integrity of a package before the material cools to ambient temperature. Evaluating hot tack allows manufacturers of flexible packaging to predict whether a heat seal will survive the mechanical forces of filling. The measurement focuses on the molten interface’s resistance to peel forces when tension is applied.
Melt Strength
Polymer density and molecular weight distribution determine the cohesive strength of the resin in its molten state. High melt strength in hot tack ensures that the seal does not peel open during automated vertical form fill seal processes. Materials with narrow molecular weight distributions often exhibit a narrow sealing window.
Process Parameter
Optimal sealing occurs within a specific temperature and pressure window. If the sealing temperature is too low, the polymer chains do not interdiffuse, which reduces hot tack, but if it is too high, the viscosity drops too far.
Packaging Consequence
Defects such as pinholes, leaks, and complete seal failures occur when packages are filled before the heat seal has solidified. By selecting a resin with superior hot tack, converting lines can run at higher speeds without risking product contamination or pouch bursting. This choice reduces packaging waste and increases overall line efficiency during high volume operations.
Furthermore, it protects the brand by preventing slow leaks during distribution.