Polyol-dependent adhesion mechanism of XDI- and H6XDI-based polyurethanes

Abstract

Polyurethanes (PUs) consisting of m-xylylene diisocyanate (XDI) exhibit excellent thermal stability and optical properties. To further enhance the optical properties, 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) is considered a potential isocyanate for optically clear adhesives; however, a detailed analysis of the adhesion mechanism has not been investigated. Herein, we synthesized PUs using diisocyanates (XDI, H6XDI) and polyols [polypropylene glycol (PPG), polycaprolactone diol (PCL), and polycarbonate diol (PCD)]. To investigate the adhesion mechanism, the interaction between each PUs and functionalized self-assembled monolayers was analyzed using a Surface Forces Apparatus at the nanoscale. Additionally, macroscopic surface energy measurement and probe tack testing were performed. Overall, higher hydrophobic interaction in PCD-containing PUs and predominant hydrogen bonding in PPG-containing PUs was measured. Also, hydrophobic interaction was stronger for H6XDI compared to that of XDI in all polyols. These findings clarified polyol-dependent adhesion mechanisms of XDI- and H6XDI-based PUs and could be used to design PUs with controlled strength of hydrogen bonds and hydrophobic interactions.

Keywords

• XDI
• H6XDI
• Surface forces apparatus (SFA)
• Polyurethane
• Adhesion