Comparative analysis by UV-vis and FT-IR spectroscopy of the chemical degradation of polyethylene used as greenhouse cover film

Abstract

Greenhouse culture usually requires a controlled environment for optimum plant growth and production. However, regular plastic films used for their coverage create an uncontrolled microclimate, especially in areas with harsh climatic conditions. Three low-density polyethylene (LDPE) films, a commercial ordinary film, a three-layer film, and a monolayer film were used as a greenhouse covering materials to study its behavior in presence of a cultivar and harsh climatic conditions. They were exposed to natural weathering and UV radiations in the semi-arid environment of a city located in northern Algeria. This study aims to investigate and compare the lifespan and deterioration of the materials used for a 5-month period to improve future greenhouse cultivation. Fourier-transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectrophotometry (UV-vis) were used to study the aging and degradation of these films. FTIR 1030/2848 bands ratio was used to determine the chemical oxidation rate of each film. Visible changes in the material structure were also recorded during the aging process. Materials underwent photo and thermo degradation, leading to chemical and mechanical changes. The monolayer film has suffered more mechanical degradation than the multilayer films, leading to its total crumbling in a short lifetime. The three-layer and ordinary films were more resistant and showed approximately the same behavior towards the rough climatic conditions. Furthermore, the UV-visible spectrum indicated a high loss of transparency of the polyethylene films during their use. The two studied multilayer films seem more adequate for greenhouse culture under the semi-arid regions.