Degradation of Thermomechanical Performance and Lifetime Estimation of Multilayer Greenhouse Polyethylene Films Under Simulated Climatic Conditions

The main objective of this work is to investigate the impact of degradation of low-density polyethylene multilayer films, used as greenhouses covers, under some desert simulated climatic conditions on their mechanical behavior, thermal stability and lifetime. The climatic conditions considered are temperature, ultraviolet (UV) radiation, and humidity which are the most detrimental factors in the ageing of the polymeric greenhouses covers. At the molecular level, the combined effects of these environmental conditions cause oxidation and severe structural modifications of the polymer which are the main mechanism of degradation. In this work, multilayer polyethylene films with 180 m overall thickness are artificially aged at different twelve combined climatic conditions of temperature, UV radiation and humidity. Deferential scanning calorimetry (DSC) analyses and mechanical tests were carried out to characterize the material and evaluate the degradation level of the thermal, physicochemical, and mechanical properties of the films. The results revealed that, the investigated broad range of climatic conditions have remarkable deteriorative impact on the performance of the film and its functionality; the highest degradation rate was under the combined effect of UV radiation and temperature ageing condition. The correlation between the created modifications in the material structure and the degradation level of cover properties and its lifetime is discussed. POLYM. ENG. SCI., 55:287-298, 2015. (c) 2014 Society of Plastics Engineers