Preparation of organic-inorganic hybrid adhesion promoters for polyurethane-metal adhesion and their properties

This study reports the synthesis of organic-inorganic (O-I) hybrid adhesion promoters, which were synthesized by an in situ sol-gel process, using alkoxysilane functionalized polymer precursor (AFAP) and other alkoxysilanes such as (3-aminopropyl)triethoxysilane (APTES) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS). These adhesion promoters were then applied between polyurethane (PU) and metal substrate for improving adhesive strength between them. In particular, by modifying the input parameters including molecular structure of AFAP, weight ratios between AFAP and alkoxysilane, and r value (molar ratio of H2O/Si), the adhesive strength can be significantly improved by more than twice as high as compared to that of pristine samples without application of O-I hybrid adhesion promoters. It was reported that the combination of (3-aminopropyl)triethoxysilane (APTES) and AFAP synthesized from glycerol propoxylate (Mw = 266 g/mol) and polyethylene glycol (Mw = 300 g/mol) with high r value showed the highest adhesive strength compared to other O-I hybrid adhesion promoters. Additionally, the properties of various hybrid materials such as particle size distribution, touch drying speed, degree of condensation, molecular weight, and adhesive strength were characterized by dynamic light scattering test, 29Si-NMR, MALDI-TOF, and shear strength test.