Polymers are widely used in the agricultural sector, in the form of containers, tanks or tarpaulins, and are frequently PE-based. However, the recycling of these wastes for new applications has not yet been fully explored. This is due to various factors, such as recycling expertise, costs, etc., but above all to the lack of reliability and knowledge of the mechanical properties of recycled polymers. In this part of the project, the focus is on characterizing polymeric materials and investigating their suitability for replacing materials such as galvanized steel, used until now in the construction of agricultural greenhouse structures. Once we have developed our knowledge of polymers, the impact of recycling on their properties and anticipated the defects that can occur during manufacture, we have set out our research priorities.
The first axis aims to establish the framework. Eight polymers are collected through the Agri- Récup and Ced-Lo recycling companies, to investigate the potential of these materials to meet the constraints of this type of application. Once the materials had been identified, visual, logistical, chemical, and mechanical acceptance criteria were established. Following these tests, LDPE, LLDPE, mLDPE and MDPE then made up the recycled raw materials, identified as A, B, C and D throughout the study. In addition, using a PP-FV30% reinforced polymer, produced by CEAD for use on their large-format additive manufacturing machine available at ÉTS, reinforced materials are formulated with 50% PE and 50% of PP-GF-30%. Once all the formulations have been carried out, the aim of the second axis is to determine all the thermal, chemical, physical, and mechanical properties of the materials. Raw polymers will be subjected to five tests: DSC, FTIR, TGA, rheology by capillary rheometer and density by Archimedes’s method. Reinforced polymers undergo pycnometer density, conductivity and thermal effusivity tests, capillary rheology, IZOD impact, tensile and flexural tests. Finally, the impact of accelerated material ageing on mechanical properties, particularly in traction, and chemical properties, by FTIR, after 56 days in conditions reproduced in the laboratory, is being monitored.
All these results show the characteristics of these 4 reinforced materials in relation to the requirements of greenhouse structures and give an initial opinion on their use: despite their mechanical capacities, which are up to 10 times less effective than galvanized steel, their use remains possible but limited.