Termosetting cabinets used for production of low voltage connectors are made of polyester resin reinforced with SMC glass fiber. This material, which is a composite polymer, is characterized by high mechanical strength and very good insulation properties.
The ageing characteristics of this material show that over time it does not lose its mechanical properties under the impact of UV radiation and weather conditions , but the visual properties of the cabinet deteriorate due to oxidation of its surface. Over time, the cabinets show color changes and appearing glass fiber. In order to improve the visual properties, varnishes resistant to UV radiation and weather conditions are used. As the result, the enclosures are not only resistant to mechanical factors, but also look aesthetically after many years.
Two factors are important when choosing the right varnish: adherence of the varnish to the polyester surface and resistance to ageing. The adhesion of various types of varnishes is tested with the cross-cut method. It consists in cutting the hardened surface with a special knife, and sticking the tape in that place. After detaching the tape, it is checked to what extend the surface has been damaged. Years of tests have shown that the best varnish products that meet both conditions are two-component polyurethane varnishes (i.e. chemically hardening). These varnishes create a coherent protective structure and guarantee optimal adhesion to the surface of the cabinets.
In order to confirm the properties of the varnish, we also conducted a series of ageing tests under UV lamps in the Quality Research Office of SEP BBJ in Lublin. These tests consisted in irradiating the varnished samples with UV lamp for 500-1000 hours. Then, using the Charpy method, we checked the material’s resistance to cracking under dynamic load. The study showed that samples protected with varnish do not show any weakening of the structure and deterioration of the mechanical resistance of the material, but they allow the color and good quality of the surface to be maintained.
Considering the above benefits and putting innovation at the forefront in our company, as the first manufacturer of thermosetting cabinets in Europe, we decided to introduce varnishing as a standard. From 15th November, each cabinet purchased from us will be varnished.