关键词: 聚氨酯, 二氧化硅, 二氧化钛, 抗紫外, 光老化, 力学性能

Abstract: "Polyurethane (PU) coatings have a wide range of application fields, with products covering numerous synthetic material areas such as foam plastics, synthetic rubber, plastics, synthetic fibers, coatings and adhesives. They are utilized in various industries including cold chains, transportation, construction, furniture, clothing, footwear, and leather, machinery accessories, food, packaging and printing, sports equipment, national defense, and military, in the forms of rigid foam insulation materials, soft foam cushioning materials, elastomeric components, microporous elastomeric footwear materials, high-elastic fibers, fabric and leather coatings, paints and coatings, adhesives, sealants and potting adhesives, waterproof and protective coatings, wood-imitation materials, and treatment agents. However, they have the disadvantage of insufficient UV resistance. In high-temperature environments and areas with strong UV radiation, they still suffer from shortcomings such as a short service life and a tendency to detachment after exposure to intense UV radiation. Therefore, in this paper, SiO2 and TiO2 nanoparticles were prepared by hydrothermal method and sol-gel method, respectively. These two types of nanoparticles were then blended with a PU solution to prepare composite coatings, which combined the good UV reflection and UV absorption properties of SiO2 and TiO2 nanoparticles, thereby improving the UV resistance of the composite coatings. This paper conducted a comparative analysis of the impact on the photoaging performance of the composite coating after adding different nanoparticles to the PU coating. Fourier infrared spectroscopy test, UV absorption spectroscopy test, XRD test, scanning electron microscopy test, transmission electron microscopy test, and mechanical property test were carried out on the coatings and nanospheres. The results showed that the SiO2 nanoparticles prepared by hydrothermal method did not form a crystalline structure, with a small amount of adhesion between the nanospheres, exhibiting good UV reflection performance. The TiO2 nanoparticles prepared by sol-gel method formed a regular crystalline structure after calcination. The nanospheres performed well in morphological test, with a relatively regular arrangement and good UV absorption performance. Their crystallinity reached 98.2%, with a crystal plane spacing of 0.35 nm. The UV resistance of the SiO2-TiO2/PU coating could be regulated by changing the blending ratio of SiO2 and TiO2 nanoparticles. When the blending ratio of SiO2 and TiO2 nanoparticles was 1:1, the obtained PU coating had the highest UV absorbance and reflectivity. At this ratio, the breaking stress and elongation at break of the SiO2-TiO2/PU coating decreased by 32.69% and 8.98%, respectively, after 30 minutes of photoaging. The decay rates of breaking stress and elongation at break of the SiO2-TiO2/PU coating under UV light were slower than those of other coatings."

Key words: SiO2, TiO2, UV resistance, photoaging, mechanical properties