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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. [ABSTRACT FROM AUTHOR]

Low density polyethylene (LDPE) is the most abundant non-degradable plastic waste. Widely used in packaging material, it represents a serious threat to all ecosystems. In the present study, a Rhizopus sp. fungal strain was isolated from soil of a landfill located in north-east Algeria and cultured on potato dextrose agar. The in vitro biodegradability of pieces of the same plastic bag (0.2, 0.4, and 0.6 g) was estimated in minimal liquid medium and on minimal solid medium. Furthermore, biodegradation of plastic bag pieces was examined in seawater, tap water and soil. The isolated Rhizopus sp. strain could degrade the plastic bag waste. The highest in vitro rate occurred in the minimal liquid medium for both the 0.4-g and 0.6-g pieces (a 20% decrease in weight). In natural media, the highest weight decrease was different depending on the substrate: 5% in seawater for the 0.2-g piece, 10% in tap water for the 0.4-g piece and 8% in soil for the 0.4-g piece. This strain could also form a biofilm in Malt Extract Broth (MEB). These results revealed that the isolated Rhizopus sp. strain has considerable biodegradative ability based on different measures. [ABSTRACT FROM AUTHOR]

The effect of washing stabilized and unstabilized blown extruded films of low-density polyethylene (LDPE) used for greenhouse coverings naturally weathered in a sub-Saharan facility at Ghardaïa (Algeria) for 19 and 6 months, respectively, was studied. A comparison between unwashed and daily washed samples was done. The changes in the films' properties were followed at regular intervals using various characterization methods (physicochemical and mechanical). Although in both cases the chemical species formed due to the weathering were qualitatively the same, they essentially differed in their concentrations, namely they were higher for the washed samples than for the unwashed ones. Inversely, the crystallinity of the washed samples was lower. Contrary to expectations, the decrease in the tensile strength and elongation at break was delayed as a result of the washing, despite a higher oxidation rate. [ABSTRACT FROM AUTHOR]

Weathering of LDPE films was performed in a sub-Saharan facility in Laghouat, Algeria. Ageing led to a rapid change of the physicochemical properties resulting from the alteration of the material's microstructure. XRD revealed the progressive increase of the crystallinity ratio and the thickness of the crystalline lamellae as well. SEM revealed the presence of white particles, which look like crystalline phase emerging from the surface of the film. The oxidation and crystallinity varied according to a concentration gradient across the thickness. The impact of the microstructural changes on the mechanical properties was highlighted based on the essential work of fracture (EWF) method. There was a progressive decrease of the total energy of fracture and a lowering of the net stress (σnet) and the (βwp) term. Nevertheless, this loss of the mechanical properties was characterized by a rapid transition from a ductile mode of failure to a very brittle mode. [ABSTRACT FROM AUTHOR]

This article focuses on the assessment and understanding of the mechanism of natural and artificial aging processes of a triple-layer film made of low-density polyethylene (LDPE) used as greenhouse cover. The film material contains color dye and ultraviolet-A (UV-A) and infrared (IR) stabilizers and antioxidant. The combined effect of temperature variations and UV-A radiations, of the natural and artificial aging, on the physical properties (free surface energy and yellow color measurements), mechanical behavior (tensile tests), thermal stability (TGA and DSC analysis), and structural stability (FTIR analysis) was investigated. The natural aging was conducted on a greenhouse, located in northern Algeria, over a period of 7 months. However, the artificial aging was performed at four different agricultural greenhouse simulating conditions of temperature and UV-A radiation (namely, at 40°C, 40°C with UV-A, 50°C, and 50°C with UV-A) for periods of aging up to 5486 h (7.6 months). The results revealed that, the maximum loss of the yellow color additives occurs at 2981 h under the natural aging process and at 2440, 1096, 1340, and 121 h under the four artificial aging conditions, respectively. There was an observed increase in the films free surface energy and a significant degradation in the mechanical properties with aging time. This can be correlated with the film material structural changes. The natural aging of the film in North Africa is almost equivalent to artificial aging at 40°C. The concurrent effect of temperature and UV-A radiations induced polymer chains scission leading to faster degradation in the film material and consequently a reduction in its durability and service lifetime. The results show also that the measured parameters are directly related to the limit of use criterion for evaluating the lifespan of agricultural greenhouse LDPE covers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

The article discusses a study of the effect of climatic ageing on the mechanical properties and microstructure of low-density polyethylene (LDPE) films conducted in Algeria. ENIP Co. has provided the commercial LDPE used in the study. Results show that climatic ageing time increases the degree of LDPE crystallinity. It concludes that LDPE films demonstrate rapid stiffening and loss of toughness following climatic ageing in the sub-Saharan region.