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[EN] In this work, we studied the mechanical performance of an LDPE film (0.22 mm in thickness) used as a material in the design of greenhouse covers. We investigated the effects of ageing at different periods of its service life and applying chemical substance treatments used as pesticides on greenhouse crops and after breakage using mechanical traction. Numerical simulations were performed using the finite element method. For this purpose, one section of the complete geometry of the greenhouse cover and different load conditions (1-5 kPa) were considered for the modelling. The performance of the polymer was assumed to be linearly elastic to simplify the governing equations. The study demonstrated that the LDPE film used was no longer effective as a greenhouse cover film due to the degradation of its mechanical properties. It was shown that the general performance of this film was in the plastic zone and its performance was non-linear. The results deduced from the present study are of interest because they show the material failure process of greenhouse covers in relation to the degradation process., [ES] En este trabajo hemos estudiado el comportamiento mecánico de un film de LDPE (0.22 mm de espesor) usado como material para el diseño de cubiertas de invernaderos. Se ha investigado el efecto del envejecimiento en diferentes períodos de la vida útil, en los que se han aplicado tratamientos con sustancias químicas, utilizadas como pesticidas en cultivos de invernadero y después de la rotura mediante tracción mecánica. Las simulaciones numéricas se realizaron utilizando el método de elementos finitos. Para la modelización se ha considerado una sección de la geometría completa de la cubierta y diferentes condiciones de carga (1-5 kPa). Además, se asumió que el rendimiento del polímero era linealmente elástico para simplificar las ecuaciones. El estudio demostró que el film no estaba en condiciones de ser usado en la cubierta del invernadero debido a la pérdida de sus propiedades mecánicas. También se ha observado que el comportamiento general de la cubierta está en la zona plástica del material y, por tanto, tiene un comportamiento no lineal. Los resultados de las comparaciones realizadas son interesantes y de gran ayuda para ilustrar el proceso de falla del material de las cubiertas de invernadero en relación con el proceso de degradación.

In this work, we studied the mechanical performance of an LDPE film (0.22 mm in thickness) used as a material in the design of greenhouse covers. We investigated the effects of ageing at different periods of its service life and applying chemical substance treatments used as pesticides on greenhouse crops and after breakage using mechanical traction. Numerical simulations were performed using the finite element method. For this purpose, one section of the complete geometry of the greenhouse cover and different load conditions (1-5 kPa) were considered for the modelling. The performance of the polymer was assumed to be linearly elastic to simplify the governing equations. The study demonstrated that the LDPE film used was no longer effective as a greenhouse cover film due to the degradation of its mechanical properties. It was shown that the general performance of this film was in the plastic zone and its performance was non-linear. The results deduced from the present study are of interest because they show the material failure process of greenhouse covers in relation to the degradation process. Resumen: En este trabajo hemos estudiado el comportamiento mecánico de un film de LDPE (0.22 mm de espesor) usado como material para el diseño de cubiertas de invernaderos. Se ha investigado el efecto del envejecimiento en diferentes períodos de la vida útil, en los que se han aplicado tratamientos con sustancias químicas, utilizadas como pesticidas en cultivos de invernadero y después de la rotura mediante tracción mecánica. Las simulaciones numéricas se realizaron utilizando el método de elementos finitos. Para la modelización se ha considerado una sección de la geometría completa de la cubierta y diferentes condiciones de carga (1-5 kPa). Además, se asumió que el rendimiento del polímero era linealmente elástico para simplificar las ecuaciones. El estudio demostró que el film no estaba en condiciones de ser usado en la cubierta del invernadero debido a la pérdida de sus propiedades mecánicas. También se ha observado que el comportamiento general de la cubierta está en la zona plástica del material y, por tanto, tiene un comportamiento no lineal. Los resultados de las comparaciones realizadas son interesantes y de gran ayuda para ilustrar el proceso de falla del material de las cubiertas de invernadero en relación con el proceso de degradación.

Since its appearance in agriculture, plastic films have revolutionized this sector with huge benefits in terms of quality and quantity of crops. In the last decades, agricultural films gained not only a great deal of interest and attention but also a big market more and more extended in any country of Europe, America, and Asia, with a constant positive trend that does not know crisis. Plasticulture is a term that indicates the world of plastic films applied in agriculture, ranging from greenhouse covers to mulches, from low tunnels to solarization films, from Totally Impermeable Films (TIF) to photo-selective films. It includes raw material (several kinds of polymers), different types of films, applications, agronomical performances, and the recycling problems. In this chapter, a review of Plasticulture is presented, from historical origins to the films extrusion technique, from their physical properties to the different typologies and uses. In particular, a new generation of agricultural films is described with characteristics, performances, and employment modalities. Finally, the new frontier of plastic films for greenhouse, with open window to UV-B radiation, is presented, considering the huge potentiality for improving further the crops quality and the increase of different nutraceutical contents in fruits and vegetables.

WOS: 000229362600003 In this study, effects of PE-UV (UV stabilised polyethylene), PE-IR (IR absorbers polyethylene), D-PE (double layer polyethylene) and PE (polyethylene) used as greenhouse covers, on growth, development and yield of aubergine were investigated over three spring seasons (1999, 2000, 2001). The greenhouse covered with PE had the highest light transmission, followed by PE-UV, PE-IR and D-PE, respectively. Based on the results, covering materials were ranked as D-PE, PE-IR, PE-UV and PE in terms of temperature in the greenhouses. Vapour pressure deficit was highest in PE, and followed by PE-IR, PE-UV and D-PE covered greenhouses. Plant growth in D-PE houses was faster than that of the plants in PE-UV, PE-IR, PE covered greenhouses. Some parameters regarding plant growth in D-PE and PE-IR covered greenhouses were found to be similar. The highest yield was obtained from the greenhouses covered with D-PE and this was followed by PE-UV, PE-IR and PE covered greenhouses. These results showed that D-PE was superior to the other covering materials for optimal plant growth and earliness of aubergine yield under the studied experimental conditions.