Passivation of Titanium Oxide in Polyethylene Matrices using Polyelectrolytes as Titanium Dioxide Surface Coating
Résumé
One of the major challenges of the polyolefins nowadays is the ability of those to resist weathering conditions, specially the photodegradation process that suffer any polyolefin. A common way to prevent this, is the use of hindered amine light stabilizers (HALS) are employed. An alternative route to avoid photodegradation is using polyelectrolites as coating of fillers such as metal oxides. Composites of polyethylene were made using titanium dioxide (TiO2) as a filler with polyelectrolytes (polyethylenimine and sodium polystyrene sulfonate) attached to its surface, to passivate its photocatalytic activity. We exposed the samples to ultraviolet-visible (UV-Vis) light to observe the effect of radiation on the degradation of coated samples, compared to those without the polyelectrolyte coating. From the experimental results, we found that polyethylenimine has a similar carbonyl signal area to the sample coated with hindered amine light stabilizers (HALS) while sodium polystyrene sulfonate exhibit more degradation than the HALS coated samples, but it passivates the photocatalytic effect when compared with the non-coated TiO2 samples. Also, using AFM measurements, we confirmed that the chemical nature of polyethylenimine causes the TiO2 avoid the migration to the surface during the extrusion process, inhibiting the photodegradation process and softening the sample. On this basis, we found that polyethylenimine is a good choice for reducing the degradation caused by TiO2 when it is exposed to UV-Vis light.
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