Light aging resistance Analysis

Sunlight exposure is a very common environmental phenomenon. During the long-term use of coatings, plastics and other polymer materials exposed to sunlight, discoloration, chalking, blistering, cracking and peeling often occur, seriously affecting the mechanical properties, appearance and other characteristics of the products. In order to evaluate the performance of materials, the artificial accelerated light aging method is often used in the light aging test of new materials.

At present, the commonly used artificial accelerated aging test methods mainly include carbon arc lamp, fluorescent ultraviolet lamp, xenon arc lamp, metal halide lamp, etc. The two methods, fluorescent UV lamp and xenon arc lamp, are mainly introduced, and correspond to the two kinds of test equipment for aging test: UV aging test chamber and xenon lamp aging test chamber.

The UV aging tester adopts fluorescent UV lamp as the light source to accelerate the weathering test of materials by simulating the UV radiation and condensation in natural sunlight to obtain the results of material weathering. It can simulate the UV, rain, high temperature, high humidity, condensation, darkness and other environmental conditions in natural climate by reproducing these conditions, merging them into a cycle, and having it automatically perform the number of cycles completed.

The xenon lamp weathering tester can be used for tests such as selection of new materials, improvement of existing materials or evaluation of changes in durability after changes in material composition. Xenon light weathering test equipment determines the light resistance of materials by exposing them to ultraviolet, visible and infrared light.

Test procedure:

The leather is exposed to artificial and natural conditions indoors for 18 months to determine what information this test can provide about long-term aging characteristics. The specimen is then evaluated to see if the change in bending stiffness shows a correlation between the two exposure types.

1. Natural Aging Method

The specimens were fixed to the sides of a wooden frame with dimensions of 50cm x 150cm. One group of leather was exposed to sunlight (south facing window) while the other group was facing in (i.e. not exposed to sunlight) and both groups were exposed to indoor conditions. This allows a direct comparison regarding the effects produced by exposure to sunlight under indoor conditions.

2. Artificial aging method

Using an in-line temperature measurement device, the surface temperature of the leather exposed to sunlight and the surface temperature of the leather samples not exposed to sunlight were measured every 12 min.

In addition, every 2 to 3 months the specimen pieces are taken and reprocessed, and in addition to the bending stiffness, the following properties are measured: tensile strength, tear strength, adhesion, flexure, rubbing fastness (DIN EN ISO 105-B02), fat content.

Artificial aging is carried out in an oven with a heat treatment temperature of 80°C and a time interval of 24h, with a maximum treatment time of 144h. The leather samples are treated for at least 24h and then tested before the next 24h treatment.