ABSTRACT
PE-films, foils and sheets are commonly used in buildings. In certain constructions, these products are in contact with wet concrete during their service life. The alkaline environment created by wet concrete may accelerate the degradation of these products.
Low-density polyethylene (LDPE) films have been investigated with respect to their durability. An accelerated ageing has been performed at 70, 80, and 90 °C in wet concrete environment and in moist air. The durability of the films in various water solutions has also been investigated. The degradation was studied with the aid of measurements of elongation at break, carbonyl index, and induction temperature. The rate of degradation in the environment of fresh wet concrete at ambient temperatures was much higher than in moist air or in other environments. Compared with unstabilised film, the time to 50 % retention of elongation at break (t50) at 90 °C for various films increases from six fold for the process-stabilised film to 100 times for the film stabilised with Irganox 1076 in the environment of fresh wet concrete. In moist air the corresponding ageing times are 3 times longer. The rate of degradation in the environment of old wet concrete at ambient temperatures was of the same magnitude as in moist air. The results show that monitoring the degree of degradation by measuring the carbonyl oxidation products does not correspond to the results from elongation at break measurements. It is demonstrated that the rate of stabiliser consumption can be detected sensitively by measurements of the induction temperature. A good correspondence has been found between measurements of the induction temperature and measurements of elongation at break. The value of the activation energy and thus the acceleration factor was found to depend not only on the stabilisation system used but also on the influencing environment.
