Preparação, caracterização e aplicação de tinta bicomponente de poliuretano à base de óleo de mamona

Abstract

Polyurethanes (PUs) constitute a class of polymeric materials notable for their extensive versatility. They can be found in various forms, such as foams, thermoplastics, elastomers and paints. These polymers result from the synthesis of two main chemical substances: isocyanates and polyols. The growing interest in the use of materials from renewable sources has led to a substantial increase in research into the total or partial replacement of these two substances. For example, polyol can be replaced by castor oil without the need for any chemical modification, in addition to the fact that castor oil is an abundant renewable source in Brazil. In this context, the objective of this study is to develop a polyurethane paint based on castor oil, since there is no mention of the development of a similar product in the literature, in accordance with the search carried out in this work. Such evidence suggests that this product is unprecedented. To achieve this objective, the samples were subjected to various analyses, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), rheology test, microbiological testing and optical microscopy (OM). The results obtained indicated that the replacement of the polyol with vegetable oil was successful, as evidenced by the appearance of the polyurethane reference bands in the FTIR spectra. XRD and DSC analyzes confirmed the amorphous nature of the polyurethanes obtained. Rheology tests confirmed the pseudoplastic behavior expected for the castor oil-based paint. TG tests demonstrated that the vegetable oil-based paint exhibited superior thermal stability than industrial paint, as well as excellent adhesion properties, comparable to commercial paint. However, microbiological tests did not show inhibition halos against fungi and bacteria in the paint developed from castor oil and in the industrial paint. Finally, the UV degradation test revealed that the vegetable oil-based paint tended to develop a yellowish color when exposed to UV rays, which limits its application in external environments subject to this exposure, however it can be applied in places internally.