Summary
Greenhouse films are used in agriculture, where they contribute to cultivation of crops. However, in Mediterranean regions, their service life is currently just over 2 years. The aim of the project is to extend their usage period to three or more years. One of the main identifiable causes of wear lies in the ultraviolet component of global solar radiation, which initiates a photochemical decomposition in the plastic. The incorporated UV-stabilising compounds do absorb most of the harmful radiation and inhibit radical chain reactions, but over time they are washed out and the films lose their protection.
Therefore, this subproject is intended to prevent migration of UV stabilisers and auxiliary materials by attachment to nanoscopically distributed sheet silicates, thus increasing the usage period.
Results:
- X-ray small angle scattering demonstrates that Tinuvin and Chimasorb are incorporated into the intermediate layers of the montmorillonite.
- Incorporation of the active substances results in an increase of the spacing from 2.5-2.7 nm to 3.85 nm for the modified montmorillonite.
- Over a short weathering period, the low density polyethylene (LDPE) films with modified sheet silicate, with the addition of PE-g-MA, show only slight changes, while ultimate elongation and tensile stress remain constant over the period studied.
- Ethylene vinyl acetate (EVA) / LDPE film results in improvements in the modulus of elasticity and tensile stress. After weathering, more UV absorbers are present in the film filled with sheet silicate than in that without sheet silicate.
- Because of the demonstrated higher retention of Chimasorb in weathered films, an extended service life is expected to result.
- The negative results of technical centre tests are preventing agricultural films stabilised with sheet silicates from being introduced in the short term.
