# Degradation of Low-Density Polyethylene Greenhouse Film Aged in Contact with Agrochemicals
## 3 Results  
Table 2 shows the results obtained by the tensile tests. Maximum strength [MPa] and percentage elongation at break [%] are reported in terms of average value and relevant bi-lateral confidence interval (95%). Figure 2: Dimensions of specimen for tensile test on greenhouse plastic film. The same values are reported in Figure 3, in terms of a bar chart displaying the mechanical property average value, positioned in the middle of its respective error bar, so as to show data visually, facilitating their interpretation. Figure 4a,b show the results of the mechanical tests, expressed in terms of maximum strength [MPa], respectively, for the samples treated with agrochemicals only once (i.e., at the beginning of the test) and the corresponding samples, undergoing two spray-coating \begin{table}
\begin{tabular}{c c c} \hline \hline
**PE-LD Film** & **Maximum Strength [MPa]** & **Elongation at Break** \\  & & **[\%]** \\ \hline (N0) & 26.00 \(\pm\) 0.95 & 716.06 \(\pm\) 22.79 \\ (N2) & 24.64 \(\pm\) 0.91 & 687.44 \(\pm\) 23.89 \\ (N4) & 20.18 \(\pm\) 1.95 & 580.87 \(\pm\) 46.41 \\ (A2n) & 20.75 \(\pm\) 2.16 & 601.16 \(\pm\) 49.29 \\ (A2y) & 21.93 \(\pm\) 2.54 & 639.46 \(\pm\) 59.15 \\ (F2n) & 16.30 \(\pm\) 3.89 & 402.33 \(\pm\) 182.78 \\ (F2y) & 21.61 \(\pm\) 3.04 & 617.55 \(\pm\) 78.51 \\ (A4n) & 13.80 \(\pm\) 1.49 & 452.04 \(\pm\) 129.48 \\ (A4y) & 18.53 \(\pm\) 2.28 & 501.79 \(\pm\) 92.76 \\ (F4n) & 10.01 \(\pm\) 1.66 & 51.06 \(\pm\) 17.24 \\ (F4y) & 16.11 \(\pm\) 2.86 & 396.47 \(\pm\) 135.39 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of tensile tests. Figure 3: Bar chart based on data in Table 2, displaying the average value of maximum strength and elongation at break, positioned in the middle of the respective error bars. Different colors in this Figure 3 are referred to the different agrochemical that has been sprayed, i.e.,: RED = Fungicide; GREEN = Anti-aphid; BLUE = No spraying. treatments. Figure 5a,b show the corresponding results, referring to the elongation at break. In all of these figures, both maximum strength and elongation at break are expressed as a percentage change over time, in relation to the same parameter when the material was new (i.e., for which, the original value was assumed to be equal to 100%). These results evidenced the same trends underscored in the \"n\" based samples, although slower kinetics of mechanical behavior decay could be observed. Hence, the repeated application of agrochemicals could have probably protected the film surface from the formation of radical groups responsible for chain scission, inhibiting the oxidative reaction with the air and slowing down the PE degradative phenomena [26]. A specific case seems to be attributed to plastic film F4n, which considerably lost its mechanical properties--mainly, its elongation at break. This is probably due to an enhanced effect on the time of the fungicide that had been sprayed, which considerably worsened the level of reliability of the same percentage elongation at break value, even after only two weeks of artificial aging. Figure 4: Ratio of aged/unaged film for each time interval of maximum strength for (**a**) virgin and after only one spray-coating samples—(N0), (N2), (N4); (A2n), (A4n); (F2n), (F4n)—and (**b**) virgin and after two (one halfway) spray-coated samples—(N0), (N2), (N4); (A2y), (A4y); (Fzy), (F4y). Finally, in terms of CI (see Table 3), the results confirmed the material's trend to quickly break down, when exposed to contact with fungicide or anti-aphid. More specifically, the CI of the untreated sample, after the first rapid worsening, underwent a weak decrease, likely associated with cross-linking reactions occurring between the carbonyl end chains of depolymerized macromolecular segments. This outcome suggests that degradation mechanisms (mostly, chain scissoring) take place during the first period of aging, mainly influenced by the formation of carboxyl and double bond terminal groups, as widely reported in the literature [41].