# Degradation of Low-Density Polyethylene Greenhouse Film Aged in Contact with Agrochemicals
## 4 Discussion
The rise in the concentration of carbonyl groups at the surface is directly correlated with the fluctuation of the absorbance value, measured at 1718 cm\({}^{-1}\), as a function of irradiation duration for the investigated materials. [PERSON] et al. [32] found a strong correlation between the increase in CI and the decrease in PE-LD molecular weight, which occurs during photo-thermal degradation. The absorption band at 1713 cm\({}^{-1}\) contained carbonyl groups, which are indicative of photo-oxidation processes. The quantity of products generated was in good agreement with variations in the carbonyl index and molecular weight. More low-molecular-weight compounds were produced as the photo-oxidation period increased. As a result of the enhanced oxygen availability at the surface layers, the oxidation of PE-LD materials produced a variety of carbonyl groups, including carboxylic acids, aldehydes, esters, ketones, and lactones. Due to the complexity of the occurring chemical photodegradation reactions, it is, however, very difficult to discern the real sequence of chain scissoring and end-group recombination in cross-linking reactions. Under the influence of the UV-A component, plastics exposed to solar radiation undergo photo-degradation, which is thought to be a major factor in the fast deterioration of their characteristics and results in scissoring and cross-linking reactions, as well as oxidation. The results of photo-degradation are frequently vinyl, hydroxyl (OH), and carbonyl (C-O) groups. Numerous experimental studies with films exposed to UV radiation have demonstrated that the increase in carbonyl residues coincides with the worsening of mechanical performances, a decrease in molecular weights, and an increase in polymer crystallinity. The correlation of these aspects was empirically proven on PE-HD materials by [PERSON] et al. [46]. Through differential scanning calorimetry (DSC), FTNIR, and analysis of the Melt Flow Index, these authors showed a strict correlation between the reduction in these parameters and the recyclability of the material, a characteristic that plays a crucial role in implementing the concept of the Circular Economy in agriculture [47]. In addition, a significant drop in the degraded film permeability to oxygen was proven by [PERSON] et al. [24,30], who showed that photo-degradation was also strongly dependent on thermal levels since it severely increased with temperature rising. In order to design the chemical formulation of the basic polymer and/or quantity and quality of its additives, it appears then possible to conclude that the results of this study are consistent with those obtained thus far in the international scientific literature. This confirms the need for further research aimed at developing an algorithm that could predict the useful lifetime of a plastic film, on the basis of the geographical location and relevant meteorological conditions, working conditions (agrochemical contamination, contact with frame steel, other environmental agents, etc. ), type of cultivation, etc. Finally, it should be mentioned that the aging of polyethylene (PE)-based materials utilized in agriculture, including greenhouse films, mulch films, and irrigation pipes, has garnered considerable attention, due to its environmental sustainability implications and the resultant production of microplastics (MPs). The degradation of these materials is significantly influenced by various environmental stressors, such as UV radiation, temperature fluctuations, mechanical stress, and chemical interactions with agrochemicals, like pesticides and fertilizers. Studies have shown that these factors contribute to the fragmentation of PE into microplastics, which poses a severe environmental challenge [48, 49, 50]. For instance, the photodegradation of low-density polyethylene (PE-LD) microplastics has been extensively studied, revealing that accelerated aging occurs under varying humidity and soil conditions, leading to significant material degradation [25].