Hybrid Coatings of SiO2–Recycled PET Unsaturated Polyester Resin by Sol-Gel Process

• Published in: Polymers Vol. 14; no. 16; p. 3280
• Main Authors: Bórquez-Mendivil, Adrián, Hurtado-Macías, Abel, Leal-Pérez, Jesús Eduardo, Flores-Valenzuela, Joaquín, Vargas-Ortíz, Ramón Álvaro, Cabrera-Covarrubias, Francisca Guadalupe, Almaral-Sánchez, Jorge Luis
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 12-08-2022; MDPI
• Subjects: Chemical synthesis; Coatings; Contact angle; Flat surfaces; Glass substrates; Glycolysis; Maleic anhydride; Mechanical properties; Modulus of elasticity; Molecular weight; Nanoindentation; Polyester resins; Polyesters; Polyethylene terephthalate; Polymerization; Propylene; Room temperature; Silicon dioxide; Sol-gel processes; Tetraethyl orthosilicate; Thermodynamic properties; Thickness; Mexico
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/polym14163280

Hybrid coatings of SiO2 and recycled unsaturated polyester resin (R-UPR) from recycled polyethylene-terephthalate (PET) were prepared by the sol-gel process on glass substrates. First, SiO2 was synthesized by the sol-gel process using a tetraethyl orthosilicate (TEOS) solution. Next, bis(2-hydroxypropyl-terephthalate) (BHPT) was synthesized from mechanical and chemical recycling (glycolysis) of post-consumer PET bottles in propylene glycol (PG) using ZnA as catalyst, in a Vessel-type reactor (20–200 °C); maleic anhydride (MA) was added and, following the same procedure, the unsaturated polyester (UP) was synthetized, which was cooled to room temperature. Next, styrene (St) and benzoyl-peroxide (PBO)-initiator were added to obtain R–UPR. TEOS (T) and three hybrid solutions were synthesized, with molar ratios of 0:1:0 (T), 1:2:0.25 (H1), 1:1:0.25 (H2), and 1:0:0.25 (H3) for R–UPR:TEOS:3-trimethoxy-(silyl)-propyl-methacrylate (TMSPM), respectively, with which TC, HC1, HC2, and HC3 coatings were elaborated using the immersion technique and polymerized (120 °C for 24 h). The solutions were characterized by FT–IR and TGA, and the coatings by SEM, nanoindentation, AFM, adhesion, and contact angle. The results showed that SiO2 enhanced mechanical (hardness and Young’s modulus) and thermal properties of the R-UPR. The coatings adhered perfectly to the substrate, with thicknesses of micrometer units and a flat surface; in addition, hydrophilicity decreased as SiO2 decreased.