Synthesis and performance of moisture curable solvent free silane terminated polyurethanes for coating and sealant applications

Abstract

AbstractPolyurethanes (PUs) constitute one of the most versatile class of polymers with respect to composition, properties, and applications. Having an excellent elastomeric performance, PUs has been used in a wide range of applications. Additionally, silane terminated modified polyurethanes (STPUs) combine advantageous characteristics of PUs and organosilicon. Two PUs and four STPUs modified by a silane end‐capper N‐ethyl‐3‐trimethoxysilyl‐2‐methylpropanamine and N‐cyclohexyl aminomethyltriethoxysilane were synthesized and acted as an adhesives or coatings which could be suitable for use in moisture‐curing compositions at room temperature without releasing CO2. The effect of isocyanate groups in the polyurethane backbone and organofunctional groups in the aminosilane structure (R1–NH–R2–Si[OC2H5]3), R1 (alkyl or aryl), the spacer R2 (α or γ) was examined. The chemical and physical structures of the PUs and STPUs were investigated by nuclear magnetic resonance (13C and 1H), dynamical mechanical analysis (DMA), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT‐IR) and the mechanical properties were evaluated by universal tensile tests. The results showed that STPUs were successfully synthesized as moisture curable, exhibiting low viscosity with adequate tensile strength and elongation can be prepared environmentally benign by utilizing secondary aminosilane end‐cappers and an optimal combination of the polyol molecular weight and NCO/OH ratio.