Interaction between titanium dioxide pigments and hindered piperidine/anti-oxidant combinations in the photostabilisation of polypropylene

Abstract

The complex interaction between titanium dioxide pigments, a primary anti-oxidant and a hindered piperidine compound in the photostabilisation of polypropylene has been examined using infrared absorption spectroscopy. The hindered piperidine compound, Tinuvin 770, was found to be ineffective in protecting the polymer against the photocatalytic action of anatase. In the case of rutile good photoprotection of the polymer was observed, the effect being greater for a coated pigment. However, the presence of the anti-oxidant, Irganox 1010, antagonised the stabilising action of the hindered piperidine compounds, the effect being greater in the presence of an uncoated pigment. The results are discussed in terms of additive adsorption onto the pigment particle surface versus the photocatalytic activity of the pigment. The effects were also found to be dependent on the ultraviolet content of the light source.