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Automakers are focusing on lightweight vehicles to address fuel economy and emission challenges and are using high-performance materials such as 2K PU-based joints as alternatives to cast iron, steel, and other metals. This study was conducted with the aim of expanding the application of 2K PU and enhancing its compatibility with steel substrates, which are commonly used in the automotive manufacturing industry, through the use of O-I hybrid nanoparticles containing alkoxysilane groups as additives in the 2K PU formulation. At the same time, the simplified process introduced and examined in this study demonstrates its feasibility for industrial-scale applications; the process offers notable advantages in reducing workload and curing time by eliminating cumbersome surface pretreatment steps before applying the 2K PU layer. Two types of commercial SB PU and EB PU were selected to study the mechanism by which O-I hybrid NPs enhance adhesion when integrated directly into the 2K PU formulation. We optimized various input parameters through practical work and modeling using the response surface method. These parameters included the amounts of AFAP precursor, APTES, and butylene glycol (BG) and the mixing ratio of O-I hybrid NPs in the formulations of two commercial PUs. The results show that O-I hybrid NPs significantly enhance adhesion, increasing performance on stainless surfaces by up to 2.35 times compared to pristine EB and SB PU. Notably, the SB PU's performance can improve up to 2.5 times according to the RSM predictions, highlighting the substantial impact of O-I hybrid NPs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]