Influence of natural and accelerated weathering on performances of photoselective greenhouse films

摘要

The research aims to investigate the effects of natural and accelerated weathering on polyethylene-based films. At this regard, monolayer films of low density/linear low density polyethylene blends, containing commercially available organic pigments and an UV absorber of the benzophenone type, have been considered. The samples were weathered on field (natural weathering) or using two different artificial procedures: UV lamp and QUV chamber. Conditioned film samples were, then, analyzed by performing several physical tests taking as-received films as a reference. Rheological measurements showed an increase in viscosity of weathered sample melts as a consequence of photodegradation phenomena, inducing the formation of double bonds and crosslinks. This latter result was also confirmed by gel content measurements. UV-visible spectroscopic tests indicated that in both cases of natural and artificial weathering an increase of the transmittance of films occurred. Tensile tests indicated the increase of films stiffness, especially in case of samples conditioned using the UV lamp, and a large decrease of the strain at break, both in machine and in transverse directions, especially for film weathered using the QUV chamber.