Low-molecular-weight oxidized materials

The formation of a layer of low molecular weight, oxidized material (LMWOM) on the surface of PP and PET films after CDT is widely accepted [10]. It is the effect of the material on adhesion that is debated. The formation of a weak boundary layer may be beneficial or detrimental to adhesion, depending on its solubility in the adhesive matrix. If the layer is soluble in the matrix, no decrease in adhesion may be observed. If, however, the layer is not soluble, this may reduce adhesion due to the presence of this cohesively weak layer at the interface. Water washing experiments were carried out to evaluate the effect of LMWOM on the surface chemistry and morphology. XPS and AFM... 

Corona discharge treatment in air proceeds through surface oxidation, which is accompanied by considerable chain scission leading to the formation of water-soluble low molecular weight oxidized material (LMWOM). 

Many low molecular weight aldehydes and ketones are important industrial chem icals Formaldehyde a starting material for a number of plastics is prepared by oxida tion of methanol over a silver or iron oxide/molybdenum oxide catalyst at elevated temperature... 

In addition to the fluoroplastics and fluororubbers already described other fluoropolymers have been marketed. Polymers of hexafluoropropylene oxide are marketed by Du Pont (Krytox). These materials have a low molecular weight (2000-7000) and are either oils or greases. The oils are uses as lubricants, heat transfer fluids and non-flammable oils for diffusion pumps. The greases are also used as lubricants. They have good heat and oil resistance but it is said that explosions may result from contact with the surfaces aluminium or magnesium cuttings. 

The author is unaware of any commerical polymers that are specifically designed to degrade oxidatively, although oxidation may be involved in association with hydrolytic and biological degradation. It may be of interest to note that before World War II products known as rubbones were produced by degrading natural rubber with cobalt linoleate in the presence of cellulosic materials to produce low molecular weight, fluid oxidised natural rubber (Section 30.4). 

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