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.
Seal Bar Fouling
Meaning
Accumulation of degraded polymer resin or migrated additives on the heated metal surfaces of packaging machinery degrades the quality of subsequent thermal seals. Preventing seal bar fouling requires careful selection of resin grades and precise control of sealing temperatures. This issue results in poor heat transfer, surface blemishes, and line stoppages.
Fouling Mechanism
Thermal degradation of slip agents or low molecular weight fractions on the hot metal jaws creates a carbonized residue. When seal bar fouling occurs, this residue acts as an insulating layer that prevents the heat from reaching the film. This uneven temperature distribution leads to inconsistent seal strength and increased scrap.
Material Influence
Resins formulated with high levels of volatile additives or low molecular weight polymers are highly susceptible to transfer. Utilizing slip agents with higher thermal stability reduces the rate of seal bar fouling. This selection allows longer production runs before maintenance is required.
Process Mitigation
Operators must implement regular cleaning schedules and utilize non-stick coatings to minimize residue build-up. When seal bar fouling becomes excessive, the sealing bars must be mechanically or chemically cleaned, causing unproductive downtime. By optimizing the sealing temperature and pressure, processors can balance the melt requirements of the film against the risk of additive degradation on the hot jaws.