Investigation of Hybrid Materials Based on Polyurethane Modified with Aliphatic Side Chains Combined with Nano-TiO2

Abstract

In this study, methylene diphenyl diisocyanate (MDI) and polytetrahydrofuran ether diol (PTMG) were used as the raw materials for the synthesis of polyurethane (PU). 1,4-Butanediol, glyceryl monostearate, d-sorbitol tetrastearate, or d-trehalose hexastearate, all containing different amounts of aliphatic side chains, were used as the chain extenders and to introduce C18 side chains into the hard segments of PU, and hybrid materials were then fabricated by mixing PUs with nano-titanium dioxide (nano-TiO2). The effects of the different chain extenders on the surface properties of PU coatings and the hybrid materials were investigated. All the materials were characterised by NMR and FT-IR spectroscopy, differential scanning calorimetry, polarising microscopy, atomic force microscopy, scanning electron microscopy, nanoindentation, and contact angle measurements. The results indicate that incremental changes in the number of side chains decrease the degree of microscale separation from the PU coating and increase the crystallinity of the aliphatic side chains. By introducing the aliphatic side chains, the surface coating presents many tiny protrusions, which enhance the surface roughness and the contact angle. Moreover, both the nano-TiO2 and aliphatic side chain content affect the contact angle of the hybrid materials. The as-obtained superhydrophobic materials exhibit contact angles above 150° with a sliding angle below 3° and present excellent mechanical properties such as hardness and Young’s modulus. The nano-TiO2 was chemically bonded to the molecular chains of PU, resulting in superhydrophobic materials with good acidic and alkaline resistance and anti-stripping properties.