Mechanooxidation of polyethylene (PH) During Processing (screw extrusion)

•The mechanochemical reaction which results from shearing of the polymer chain is typified in the above schematic.•Hydroperoxides produced in the polymer at this stage subsequently sensitize the fabricated product to further oxidation.•The Willow Ridge catalytic additive reduces the energy necessary for further chain scission.

Formation of low Mw carboxylic acids and esters in the oxidation of polyethylene

The Willow Ridge catalyst technology allows the free radical products produced during processing to transform into lower Mw carboxylic compounds initiated by ambient heat, UV energy, and time.

This process can be monitored by the increasing absorbance of the carbonyl (C=O) functional group through FT-IR analysis, as well as Mw measurements through HPSEC analysis.

The change in the chemical structure of the polymer also changes the hydrophobicity, and as a result allows for the polymer to be readily assimilated by microorganisms once they come in contact with the microbes.

However, the oxidation products are not extractable by water or by a 0.1 N NaOH solution medium, which relates to no migration issues for food contact applications.

Summary of polymer oxidation

Oxidation involves three distinct phases; Initiation, Propagation, and Termination.

Initiation begins in the screw extruder with the introduction of hydroperoxides. Reaction (e) is the rate determining step as the microbial biodegradation will follow the oxidation growth rate measured by looking for the carbonyl groups formed in reaction (h).

The Willow Ridge technology lowers the activation energy necessary to promote complete oxidation and serves as a vehicle to control a steady oxidative-degradation rate, which will convert into a steady biodegradation rate once the material is properly disposed of and comes into contact with microbes.