Guido Jozefina Wilhelmus Meijers

Comparison of the UV-degradation chemistry of polypropylene, polyethylene, polyamide 6 and polybutylene terephthalate

The photodegradation mechanism of polymers highly depends on the type and concentration of chromophores present. This influence is studied by making a comparison between the UV-degradation of PE, PP, PA6 and PBT and the thermooxidative degradation of PP at a comparable temperature. The degradation processess are followed by determining the oxygen uptake, CO, CO2 and peroxide formation. During UV-degradation of PP, PE, PA6 and PBT the oxygen uptake is linear in time without an induction period. The oxidation rate of PP is higher than that of PBT, which is slightly higher than the oxidation rate of PA6, while that of PE is the lowest. The determined amount of peroxides depends on the ageing time. For the UV-degradation this does not lead to the expected increase of the oxidation rate, as is the case with thermooxidation of PP. Only a limited proportion of the peroxides formed during the UV-degradation decomposes into radicals. The oxidation rate is mainly determined by other radical forming reactions. In the case of PE and PP this is probably initiation by polymer-oxygen Charge Transfer Complexes (CTCs) and for PA6 and PBT direct photolysis of the amide or the ester linkage, respectively. Thickness degradation profiles show that the UV-degradation processes of PP and PBT are heterogeneous. For PP this is due to oxygen diffusion limitation, while in the case of PBT it is the result of absorption of the UV-light.

Influence of environmental concentrations of ozone on thermo-oxidative degradation of PP

Abstract Recently it was postulated that natural variations of ozone concentration could have a big influence on the oven stability of polypropylene (PP). To examine this hypothesis the influence of low concentrations of ozone (comparable with environmental concentrations) on the thermo-oxidative degradation rate of PP-films was determined. PP-films were aged in a draft air oven with and without the addition of a small amount of ozone (maximum concentration ozone in the oven was 100–200 μg/m 3 ). The decrease of the elongation at break as function of oven ageing time was determined. It is shown that changes in the environmental concentrations of ozone have no significant influence on the rate of degradation in an oven.

38.2: High Performance Single Layer Anti‐Reflective Coatings via Wet UV Curing Technology

Here we present a novel manner for preparing single layer anti-reflective coatings with excellent optical properties (<1% reflection) over a broad wavelength regime. The technology is based upon the self-assembly and UV curing of reactive nano-particles, leading to nano-structured coatings with a gradient in refractive index. The single processing step leading to such coatings is fast, robust and cost effective.