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.
Thermal Sealing
Meaning
Fusing two thermoplastic films together using controlled applications of heat, pressure, and dwell time creates a hermetic barrier for packaging applications. The process of thermal sealing relies on the interdiffusion of polymer chains across the molten interface to form a unified structure. This method is the primary technique for producing pouch, bag, and tray closures.
Process Parameter
Sealing temperature, contact pressure, and jaw dwell time must be balanced to achieve optimal weld strength. During thermal sealing, heat must penetrate the outer non-melting layer to melt the inner sealing sealant layer. Insufficient heat input results in interfacial failure.
Interface Welding
Polymer chain entanglement across the joint plane dictates the final strength of the fused boundary. In thermal sealing, the temperature must exceed the melting point of the sealant resin to mobilize the molecular chains. Cooling the joint under pressure ensures that crystallization locks the chains in place.
Commercial Application
High speed packaging lines require materials that weld rapidly to maintain throughput without compromising seal integrity. When thermal sealing is executed correctly, the weld strength of the seal exceeds the tensile strength of the film itself, causing the package to fail in the body rather than at the joint during stress testing. This reliability is essential for food and medical packaging where contamination must be prevented.