Meaning
Thermal breakdown of primary slip agents occurs when secondary fatty acid amides lose structural integrity during high shear plastication. Polyethylene film extrusion relies on this additive migrating to the surface to lower friction coefficients. Excessive barrel temperatures drive molecular cleavage, yielding volatile breakdown products that ruin seal strength and laminate adhesion.
This chemical deterioration prevents the additive from blooming properly, leading to severe web blocking on winders.
Thermal Threshold
Melt temperatures exceeding standard processing windows accelerate the cleavage of primary carbon chains. Excessive residence time in the barrel magnifies shear heating, causing the organic slip molecule to break down prematurely. Cooling inefficiency downstream compounds the issue by trapping degraded fractions within the amorphous regions of the film.
Coefficient Penalty
Friction values spike unpredictably when molecular cleavage reduces the surface migration rate of the active slip agent. Packaging lines experience high drag forces across forming collars because degraded molecules fail to form the required boundary layer. Moulders target exact additive loading rates on resin datasheets, but thermal abuse during compounding wipes out those laboratory gains before the melt reaches the die.
Molecular Failure
Weakened seal integrity damages final pouch conversions, resulting in leaking seams and scrapped customer lots. Processing scrap generated from thermal breakdown cannot return safely to the virgin feed stream without causing severe extruder surging. Regrind economics suffer immediately because recycled polymer containing degraded slip fractions destabilizes bubble stability on blown film lines.
