Meaning
The quantitative concentration of fatty acid amide molecules migrating to the exterior boundary of extruded polyolefin films dictates surface slip performance and surface energy. Controlling surface amide density prevents film blocking on storage rolls while maintaining acceptable printability and seal strength. Slip additives such as erucamide or oleamide dissolve in the molten polymer during extrusion and migrate toward the film interface during cooling.
Excess accumulation leads to greasy surfaces and heat seal failure in flexible packaging applications.
Migration Dynamics
Diffusion rates of slip additives through the semicrystalline polymer matrix determine the time required to establish stable kinetic friction coefficients. Achieving target surface amide density requires careful control of storage ambient temperature and polymer crystallinity levels. Fast blooming oleamide reaches film surfaces within hours, whereas erucamide migrates over several days to provide long term slip stability.
High storage temperatures accelerate additive diffusion, causing excessive surface accumulation that interferes with downstream corona treatment and laminating adhesives. Molders and film converters evaluate blooming kinetics to balance immediate handling requirements against downstream conversion processing. Inconsistent additive distribution across the film web creates localized variations in coefficient of friction that jam automated packaging equipment.
Frictional Impact
Reduction of surface friction allows high speed automated packaging machinery to form and seal polyolefin bags efficiently. Optimizing surface amide density lowers static and kinetic friction coefficients below point two zero without sacrificing optical clarity. Uncontrolled slip additive migration creates severe surface haze on clear film structures.
Measurement Technique
Surface spectroscopy methods quantify chemical additive concentrations present on film boundary layers. Determining surface amide density utilizes attenuated total reflectance Fourier transform infrared spectroscopy to measure carbon oxygen double bond absorbance peaks. Standardized testing ensures additive levels remain within target packaging specifications.
