Aging of polyethylene textiles for the design of mosquito-proof shield adapted to tropical environment

This study is part of a project initiated by the ARS (Agence Regional de la Sante) in Guadeloupe to fight against the spread of the mosquito Aedes aegypti in the past years. These mosquitoes are responsible for several major tropical diseases outbreaks such as the dengue fever, Chikungkunya and more recently Zika. The finality of this project is to design and manufacture a mosquito-proof shield product to prevent larvaes of mosquitos to develop in rain recuperation reservoir and thus to reduce the mosquito population and the infection risk. Such screening needs to be mechanically resistant and durable under our tropical environment. In this work, we investigate two polyethylene nets, i.e. PEB (Black color polyethylene) and PEG (Green color polyethylene). These materials offer a high flexibility, are water permeable and have small enough meshes to prevent mosquitoes to reach the water contained in the reservoir. Artificial aging of these polymeric materials was realized using an accelerated UV aging chamber, the ARTACC whereas natural aging was performed either in Bandol (south of France) or in Guadeloupe. The chemical degradation of the polymer has been characterized by IRTF spectroscopy by following the evolution of the carbonyl ratio and oxidative index at the wavelength of 1715 cm-1. The mechanical properties have been measured using of a universal traction testing machine. We found that the mechanical properties of the PEG material dropped by 80% after 32 days of accelerated aging. The IRTF analysis showed a progressive chemical degradation during the aging process. In the case of the PEB, no mechanical loss was observed after 62 days of artificial aging indicating a good chemical stability. For this PEB material, the black color is due to the presence of carbon black additives. These additives are responsible of the high absorption rate in the infrared spectrum and prevent the determination of the carbonyl ratio and the oxidative index. Natural aging data are in good agreement with these results. After 6 months of natural ageing no mechanical modification was observed for PEB samples or PEV in Bandol. For PEV samples aged in Guadeloupe a 25% dropped of the mechanical strength was observed leading to an accelerated factor close to 9. These combined results clearly indicate that PEB is the best net candidate for durable mosquito-proof shield.