![]() ![]() ![]() It is a group of pigments used to color poly (vinyl chloride) plastisols, polymer products and paints whose coatings are resistant to high temperature, chemical agents and solar radiation. In this paper, yellow, orange and red cadmium pigments consisting of cadmium sulphide or their crystalline mixtures with cadmium selenide were selected for research. The results of research on the properties of cadmium pigments after chemical exposure and UV irradiation as well as of polyvinyl chloride plastisol membranes, including their presence before and after UV irradiation, are presented in other studies 10, 11, 12. A simplified mechanism of the PVC dehydrochlorination process was included in the work of Rodolfo and Mei 9. ![]() This process is known as dehydrochlorination. Further reactions may lead to the development of other types of cadmium.Įxposure of the PVC polymer to ultraviolet light can release hydrogen chloride (HCl) accompanied by the formation of polyene sequences and cross-links in the chain, causing a rapid degradation process, usually manifested by a color change from yellow to dark brown. It involves the direct photo-oxidation of cadmium sulphide to cadmium sulphate. The complex mechanism of CdS yellows photooxidation under the influence of light and moisture was presented in the work of Van der Snickt et al. They also studied compositions of white pigments with cadmium yellow and red pigments being mixtures of cadmium sulphide and cerium sulphide. Auger and McLoughlin 6 investigated colour fading of acrylic coatings with titanium white of rutile structure and yellow pigments when exposed to UV radiation. The degradation of materials is influenced to a lesser extent by the concentration of ozone, sulphur dioxide, heat and humidity. The results of the colour measurements suggested that the factors which had the greatest impact were light and the mixture of nitrogen oxides. Colour changes of carboxymethyl cellulose, polyamide, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polycarbonate, polyurethane, melamine–formaldehyde and phenol–formaldehyde resins were measured. 5 studied the effect of heat, humidity and light on the degradation of polymeric materials in the natural environment. The change in the colour of polyamide products was caused by thermal degradation products as well as leaching and hydrolysis of copper-containing compounds. The products were coloured with copper complexes and compounds, phthalocyanine blue and cobalt pigments. Bigger, Gribben and Rogers 4 investigated the change in colour of polyamide products aged in water. The durability of the composites increased when titanium dioxide of rutile structure was added to PVC. It was found that wood fibres accelerated the degradation of the composite caused by radiation. The samples of composites were irradiated with UV lamps. 3 examined the weather resistance of titanium dioxide-pigmented composites of polyvinyl chloride with wood fibres. Studies have not shown to improve the optical properties of the PVC plastisol containing titanium oxide and pearl. The spectral properties of solar radiation for PVC plastisol films with various fillers have been described by Jaoua-Bahloul et al. The most interesting research issue is explaining the effects and causes of the color change of pigments and the properties of polymer products under the influence of UV radiation. Coloring of plastics is one of the factors determining the so-called life cycle of the product made of the material 1. Pigments in paint coatings fulfill decorative and protective functions. The calculations allowed for the determination of the effect of UV irradiation on the change of the colour of the membranes and confirmation of the degradation of the pigments and polymer membrane. Base of them, the tolerance of colour deviations (ΔE*) was determined. ![]() The color change of the membranes was determined from the spectra obtained by reflection spectroscopy, and the components of colour L*, a* and b* were calculated. The degree of crystallinity of the pigments and the membrane was determined by X-ray diffraction. The changes occurred in the PVC membrane were investigated by thermogravimetric analysis. The surfaces of the coloured membranes were examined by infrared spectroscopy before and after irradiation with UV. The pigments were used to color the poly (vinyl chloride) plastisol films, which were then exposed to UV radiation. Their quantitative composition and specific surface area were examined. They consisted of cadmium sulphide and cadmium sulphide with zinc sulphide as well as cadmium sulphide with cadmium selenide. The cadmium pigments were yellow, orange and red pigments. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |