Repsol YPF

Duration tests: accelerated artificial aging

The degradation that agricultural films suffer due to exposure to bad weather occurs in a scale of times that is too long when what we want to know is if the modifications that are introduced in the formulations represent an improvement with regard to the original compounds. The objective of carrying out tests in chambers with artificial light sources is to try to obtain information regarding the behaviour that each material would have when being exposed to bad weather, but in a shorter period of time and under controlled conditions.

Xenon arch lamps and fluorescent ultraviolet stand out among the different types of light sources that have been used. The following graph shows the spectrum of solar light as compared with that of the two previous lamps. As you can observe, the first of them reproduces with sufficient approximation the spectrum of solar irradiation in the ultraviolet and visible regions when appropriate filters are used. The ultraviolet light that is used at the present time is much more energetic since all its irradiation is concentrated on the UV-B zone (maximum to 313 nm).

The chambers that are marketed for the artificial aging of samples in the laboratory allow acting on three of the factors that accelerate the degradation processes: radiation, temperature and relative humidity (condensation). There are standardized methods in which the most appropriate values are indicated for each test: ISO 4892; ASTM D 2565, G 151, G 154, G 155; UNE 53104, 53328. The criteria that is habitually used to consider a sample to be degraded, is that its lengthening at the rupture point be less than 50% of the value of the same sample without aging.