# Agrochemical Contamination and Ageing Effects on Greenhouse Plastic Film for Recycling
## 5 Discussion  
The results obtained during this research show that the contact with agrochemicals plays a decisive role in the degradation process of the plastic film, confirming that agrochemicals generate by-products leading to degradation of greenhouse films together with a decrease in their mechanical and physical properties. The degradation due to agrochemicals was found to be dependent on their active principles, as well as on method and frequency of application. From the analysis of the decrease in the mechanical properties, it is possible to deduce that the effect of the UV radiation on the PE-LD film was revealed to be dominant, as expected, since it has been the main driver of the decay (Figures 3 and 4). On the other hand, the synergistic effects and the relative importance of exposure to the two different agrochemicals in the degradation of the films were significant as well. Indeed, from the three treatments which have been applied--i.e., ageing after exposure to radiation only; ageing after exposure to radiation plus anti-aphid chemicals; ageing after exposure to radiation plus fungicide--there is an evident increase, according to this order, in the decay of both maximum strength and percentage elongation at break. Since the reduction in the elongation at break below the 50% of the virgin material is considered the technical criterion for defining the end of the useful working period and consequent need to remove the plastic film, it is clear that the contact with agrochemicals significantly worsens the ageing process of the plastic film, thus conducting to a reduced working life. This increased reduction in mechanical properties boosted by the contact with agrochemicals, also entails that when entering the recycling stage, the material carries a low potential for being transformed into a closed-loop recycled material. This phenomenon is particularly clear in the case of PE-LD plastic film having been in contact with the fungicide, that has almost lost every mechanical property after 4 weeks of artificial ageing. In this case, its mechanical recycling would deliver a recycled material with no potential applications as a film. This is particularly true when considering the degradation occurring in polymers consequent to mechanical recycling, due to thermo-mechanical processes [30; 31; 32]. The results presented here seem in accordance with several studies, which have been conducted to evaluate how agrochemical contamination is contributing to the concurrent action of other natural factors in the ageing of the plastic film used for covering greenhouses. Indeed, [PERSON] et al. [33] analyzed the quantitative criteria which may be combined as a basis for the characterization of the degradation of PE-LD films (currently the most widespread greenhouse covering material in Mediterranean countries). The authors argued that the final characterization of the degradation of a greenhouse plastic film is mainly based on the change in percentage elongation at break. In this sense, the exposure of PE-LD film to weathering conditions (especially to solar irradiation in the range of 290-400 nm) affects its chemical structure and, consequently, its mechanical and physical properties. [PERSON] [34] analyzed the synergistic effects of accelerated ageing on PE-LD greenhouse film by using an aggressive agrochemical (Vapam) under UV radiation. A non-stabilized film was used, in order to investigate the basic characteristics of ageing over a very short period. The ageing was assessed through changes in selected mechanical properties of the film, before and after ageing. A modified artificial ageing procedure was finally proposed, which was considered to simulate the weathering of PE-LD greenhouse film in a more realistic way. A series of experimental multilayer films, exposed to accelerated \begin{table}
\begin{tabular}{c c c} \hline \hline
**PE-LD Film** & **0-2 Weeks** & **0-4 Weeks** \\ \hline N & +31.3\% & +28.5\% \\ \hline A & +16.1\% & +26.0\% \\ \hline F & +21.4\% & +42.4\% \\ \hline \hline \end{tabular}
\end{table}