Experimental creep test sensibility of mechanical properties of LDPE films used as greenhouse roof.

Plastic films are widely used in agriculture throughout the Mediterranean area and the rest of the world, but their impact on the sustainability of agricultural production and the environment is a major concern. One of the factors limit-ing the recycling of agricultural plastics is the loss of mechanical properties due to ageing from exposure to exter-nal agents. This research analysed the degradation of the mechanical properties of LDPE films used for greenhouse roofs by naturally weathering them for nine months in harsh climatic conditions in the Tiaret region of Algeria. Tensile and creep-recovery tests were conducted to measure changes in the mechanical properties of both monolayer and tri-layer films, and the anisotropic character of the films was preserved during ageing. Cross linking improved the creep resistance for both types of films but affected different defor-mations. Results show that the degradation performance of the new tri-layer films is significantly better than that of the monolayer film with regard to mechanical properties. There-fore, it can be concluded that the erosion of greenhouse LDPE film by temperature, water, sand particles, wind, and humidity results in an extreme lifetime limit. LDPE film may have a longer period of use in Mediterranean Europe (with lower temperatures and no sand-wind effects) than in North Africa (with high temperature and adverse sand-wind effects).