# Degradation of Low-Density Polyethylene Greenhouse Film Aged in Contact with Agrochemicals
## 2 Materials and Methods  
Monolayer PE-LD plastic film, extruded through blow-extrusion technology into a nominal thickness of 200 \(\upmu\)m (density: 0.92 g/cm\({}^{3}\)), typically used for covering greenhouses, was examined in this study. Samples from this film, having dimensions 420 mm \(\times\) 200 mm, were obtained, so as to get ten specimens from each sample type, to be subjected to tensile and spectro-radiometrical tests. These samples were initially spray-coated alternatively using two different agrochemicals, largely used by greenhouse farmers in Southern Italy, i.e., the anti-aphid insecticide EPIK SL VITHAL (active ingredient: _Acetamiprid_ 50 g/L-producer: Ital-agro srl) [34] and the fungicide CUMETA FLOW (active ingredients: _Metalaxil-m_ 1.85%, copper hydroxide sulfate 15.40%, producer: Diachem S.P.A) [35]. These two agrochemicals were sprayed on one side of the plastic film as they were, by using a nebulizer spraying at a distance of 30 cm from the film surface. Then, the spray-coated films were artificially aged for 2/4 weeks at 20 \({}^{\circ}\)C, RH 60%, and UV radiation 1000 W m\({}^{-2}\), in a chamber for artificial aging (CO.FO.ME.GRA SolarBox 3000e) at the Laboratory of Rural Buildings and Agro-Forest Land Planning--Material Testing Section--of the University of Basilicata (Italy). The duration of this artificial aging process was chosen to simulate an aging period in an open field in Southern Italy (i.e., Apulia Region--Province of Bari), where a total of about 4850 MJ m\({}^{-2}\) (116 kLy) of solar energy has been measured to come on average every year. Given that the aging chamber's bulb emits energy with a power of 1000 W/m\({}^{-2}\), this figure roughly equates to eight weeks of artificial aging, i.e.,:  
\[8\text{ weeks}\times 7\text{ days/week}\times 24\text{ h/day}\times 3600\text{ s/h}\times 1000\text{ W m}^{-2}=4838.4\text{ MJ}\text{ m}^{-2}\]  
Therefore, the two- and four-week testing periods of artificial aging roughly correlate to three and six months of natural aging exposition, respectively. These conditions for conducting the tests were chosen for the present research because there is no specific ISO/ASTM standard dedicated to the aging of greenhouse PE-LD films. Some relevant standards would be used to assess the degradation and performance of these films, but they provide general guidelines for testing plastics and accelerated aging, so their adaptation to the specific requirements of a greenhouse PE-LD film and agrochemical exposure conditions appears quite difficult. The spraying of these two agrochemicals was repeated halfway through the aging period, i.e., after 1 week (in the case of the total aging duration of 2 weeks) and after 2 weeks (in the case of the total aging duration of 4 weeks), so as to simulate the ordinary conditions employed by farmers to protect their crops against plant diseases. The untreated PE-LD film samples, both unaged (N0) or aged for 2 weeks (N2) and 4 weeks (N4), were analyzed too, as reference samples. The following samples with their identification codes--based on the type of used agrochemical (A for anti-aphid, F for fungicide), weeks of artificial aging (0, 2, 4), and \"yes\" or \"no\" halfway repetition of agrochemical spraying (y, n)--were analyzed (Table 1): (N0), (N2), (N4); (A2n), (A4n), (A2y), (A4y); (F2n), (F4n), (F2y), (F4y). For example, the sample (F4y) is PE-LD film sprayed with fungicide (F), aged four weeks in the artificial aging device (4), and halfway sprayed (y). After the aging process, all samples were subjected to tensile tests by using a Galdabini PMA10 Universal testing machine (Figure 1) equipped with a 5 kN load cell, located at the University of Basilicata, Italy (DAFE Department--Laboratory of Rural Buildings and AgroForest Land Planning--Material Testing Section), at 20\({}^{\circ}\) room temperature and 45 \(\pm\) 5% RH.