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 lm 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.
Few attempts are available in the literature on utilising the trilayer low density polyethylene (LDPE) film as new generation of greenhouse cover to substitute the monolayer film that is often used. This paper investigates and compares the degradation behaviour and durability of both covers. The covers are exposed to 7 months of natural withering. The results revealed that the degradation resistance of trilayer film is better than the monolayer film in terms of their mechanical and optical properties. The service lifespan, based on 50% reduction in the property criterion, of the trilayer film is found to be double the service lifespan of the monolayer film.
This work aims at studying the degradable effect of artificial ageing on tri-layer stabilised lowdensity polyethylene (PE) films used as greenhouse cover in the North Africa environment. The film was supplied by Agrofilm company, Algeria. Colour additives and infra-red and ultraviolet stabilisers were used. Optical, thermal, surface and mechanical properties have been investigated for virgin sample and samples exposed to sand wind for different exposure periods (1, 2, 4 and 8 h) of artificial ageing at a temperature of 40°C simulating Saharan environment. The findings of this study show that the harsh environmental conditions of exposure to temperature and sand wind have significant degradable effects on the properties of the PE film. The transmission of the film and its mechanical properties have reduced significantly due to exposure to sand wind and temperature. The study revealed also that the degradation parameters measured are directly related to the criteria for evaluating the effectiveness of agricultural greenhouse
In this work the performance and durability of a new generation of greenhouse covers, in which the cover is composed of five layers, are investigated. A sand wind ageing was performed under different exposure conditions. Surface morphology and chemical, physical, and thermal characteristics were investigated by using optical microscopy, FTIR, and tensile test techniques. In addition, the mechanical integrity of the five-layer film was assessed. The analysis indicated that the sand wind treatments have a significant influence only on the performance of the film. An attempt has been done to compare the properties of the five-layer film with the monolayer and trilayer films with or without air bubble under similar conditions. The results revealed that the five-layer film proved to be a promising greenhouse covering film.
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