Analysis of long-term degradation behaviour of polyethylene mulching films with pro-oxidants under real cultivation and soil burial conditions

Abstract

Apart from the conventional polyethylene and the bio-based or mainly bio-based biodegradable in soil mulching films, polyethylene mulching films of controlled degradation in soil are already used in agriculture. The use of special pro-oxidants as additives is expected to accelerate the abiotic oxidation and the subsequent chain scission of the polymer under specific UV radiation or thermal degradation conditions, according to the literature. The role of pro-oxidants in the possible biodegradation of polyethylene has been theoretically supported through the use of controlled laboratory conditions. However, results obtained in real soil conditions, but also several laboratory test results, are not supporting these claims and the issue remains disputed. Mulching films made of linear low-density polyethylene (LLDPE) with pro-oxidants, after being used for one cultivation period in an experimental field with watermelon cultivation, were buried in the soil under real field conditions. This work presents the analysis of the degradation of the mulching films during the cultivation period as compared to the corresponding changes after a long soil burial period of 8.5 years. The combined effects of critical factors on the photochemical degradation of the degradable mulching LLDPE films with pro-oxidants under the cultivation conditions and their subsequent further degradation behaviour in the soil are analysed by testing their mechanical properties and through spectroscopic and thermal analysis.

Degradation in soil behavior of artificially aged polyethylene films with pro‐oxidants

“…28 The serious embrittlement explains the high degree of fragmentation experienced during the burial of the UV treated samples compared to the naturally aged ones. 28 The serious embrittlement explains the high degree of fragmentation experienced during the burial of the UV treated samples compared to the naturally aged ones.…”

“…27 This implies that a much longer soil burial period is needed for a possible fragmentation of these remains to the degree of invisible micro-fragments experienced by the samples exposed artificially to intensive UV-A/UV-B radiation. 28), polluting the soil and the water. 27, polyethylene mulching films with prooxidants are strongly degraded during their useful life-time under the solar UV radiation and summer temperatures (depending on the composition of the polyethylene mulching films, the type and percentages and the ratio of pro-oxidants to UV-stabilizers).…”

“…28, considers that the presence of radicals formed during aging can lead to the formation of crosslinks in conditions of oxygen absence (e.g. 28, considers that the presence of radicals formed during aging can lead to the formation of crosslinks in conditions of oxygen absence (e.g.…”

“…28 The aim of the present work was to simulate the behavior of LLDPE mulching films with pro-oxidants (same films were used as in Ref. The remains of these naturally aged materials remained intact after 8.5 years in the soil, even though they were further degraded.…”

Physical and Degradable Properties of Mulching Films Prepared from Natural Fibers and Biodegradable Polymers

“…However, the major problem associated with the use of non-biodegradable plastic films is that they can pollute soil when they are buried in landfills; in addition, the removal and disposal of these plastic residues from the field either before or after harvest is costly and time-consuming [1,5]. For these reasons, farmers usually incorporate used films into the soil; occasionally, they burn the used plastic films, causing harmful pollution [6]. In order to increase the sustainability of agricultural practices and to overcome the disposal problems associated with conventional plastic films, the development and use of mulching films based on biodegradable materials is highly desirable.…”