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.
Oleyl Palmitamide
Meaning
Organic fatty acid amides function as internal and external lubricants to improve the handling of polymer films and moulded parts. Oleyl palmitamide is a secondary slip agent that reduces the coefficient of friction on the surface of polyethylene and polypropylene. It works by migrating out of the polymer matrix to form a thin, lubricating layer.
This additive is often chosen for its high thermal stability compared to primary amides like erucamide.
Surface Migration
Efficiency of the lubricant depends on its ability to reach the surface at a controlled rate. Oleyl palmitamide moves through the polymer structure after processing, a process that can take several days to reach equilibrium. The final surface concentration is influenced by the crystallinity of the resin and the storage temperature.
Moulders must wait for this migration to finish before measuring the final friction properties of the part.
Friction Reduction
Lowering the resistance between the plastic and metal surfaces prevents the material from sticking to the mould or the packaging equipment. Using oleyl palmitamide ensures that high-speed production lines can operate without frequent interruptions caused by part jams. The lubricant also prevents the film from blocking, which is the tendency of two layers of plastic to stick together.
This performance is primary for the manufacturing of bags and pouches.
Bloom Stability
Persistence of the lubricating layer over time is a performance metric for slip additives. Because oleyl palmitamide has a higher molecular weight than some alternatives, it tends to stay on the surface longer and resist being wiped off. This stability is important for parts that will be handled frequently or stored for long periods.
Choosing the right concentration prevents an excessive bloom, which could interfere with printing or labeling. Proper loading levels balance immediate slip performance with long-term surface quality.
Interfacial Crystallization Mechanisms of Secondary Amides under High Pressure Thermal Sealing Conditions
High sealing pressure forces secondary amides into ordered interfacial crystal networks, preventing weak boundary layer formation and maintaining hot tack.