Desenvolvimento de nanocompósitos poliméricos visando aplicação como revestimento térmico e bactericida para construção civil

Abstract

The optimization of the thermal performance of buildings, along with the promotion of healthier indoor environments, is a continuous demand in the construction sector. In this context, the research and application of materials that enhance the energy and environmental efficiency of buildings becomes essential. Nanometric-scale materials, known as nanomaterials, exhibit interesting properties that, when applied in small quantities in the production of nanocomposite materials, can improve or develop new functionalities. Examples include graphene oxide (GO) and silver nanoparticles (AgNPs), which are nanomaterials that demonstrate antibacterial properties, mechanical strength, and thermal stability, among other properties. Aiming to contribute to the improvement of thermal comfort, combined with cleanliness and hygiene, in long-term occupancy environments, this research focuses on the development of hybrid materials incorporating AgNPs and GO into polymeric matrices for use as coatings (paint) in civil construction. In the first stage of the research, GO and AgNPs were synthesized, and the experimental conditions for developing nanocomposites using latex technology were optimized. The proportions of the nanostructures, the concentration of the AgNPs solution, and substrate tests were defined. The precursor materials were characterized by UV-vis spectroscopy and atomic force microscopy (AFM), GO by potentiometric titration and thermogravimetric analysis (TGA), and AgNPs by X ray diffraction (XRD). The films were morphologically characterized by AFM and scanning electron microscopy (SEM). Structural analyses were also performed, including infrared spectroscopy, Raman spectroscopy, mechanical and thermal analyses using infrared thermography. To assess antibacterial activity, microbiological analysis was conducted according to the CLSI M02 protocol, with modifications as necessary. The results show that the synthesis of the precursor materials aligns with the literature, displaying the characteristic peaks of GO and AgNPs. The XRD results of AgNPs confirm the reduction of silver ions to metallic silver nanoparticles. SEM results demonstrate good homogeneity of the nanocomposites, with no loose structures and nanoparticles well adhered to the polymer matrix. AFM images reveal that the presence of CTAB aids in the coalescence process of latex particles, and that sample roughness increases with the concentration of reinforcements. Furthermore, the nanocomposite samples exhibited lower hardness than the pure matrix, as well as greater adhesiveness. FTIR spectroscopy indicated that the incorporation of nanostructures does not alter the matrix structure. In tensile deformation mechanical analyses, the isolated presence of reinforcements in the matrix, as well as most nanocomposites, increased the Young’s modulus; however, the sample with both components in intermediate proportions – 1AgNP1GO – showed greater flexibility and elongation. Microbiological analyses did not indicate antimicrobial or antifungal activity of the nanocomposites, which may suggest particle aggregation, concentration issues, or isolation by the matrix. Thermographic analyses revealed that the 2AgNP2GO nanocomposite exhibited a surface temperature difference of up to - 4°C compared to other samples, indicating its potential as a promising coating material to enhance the thermal performance of buildings.