Mechanical Properties, Thermal Stability, and Glass Transition Behaviors of a Waterborne Polyurethane/Graphene Oxide Nanocomposite

Abstract

We synthesized anionic waterborne polyurethane (aWPU) from IPDI (di-isocianate), PTMG (diol), DMPA (anionic ionomer), TEA (neutralizer), and BD (chain extender). Cationic WPU (cWPU) was also prepared using MDEA (cationic ionomer) and HCl (neutralizer) instead of DMPA and TEA. Since the graphene oxide (GO) is anionic due to the -COOH group, GO and aWPU are not compatible because of the repulsive force between identical ionic charges. Thus, we fabricated cationic surfactant treated GO/aWPU to increase the compatibility. cWPU/GO, where attractive forces act between anionic GO and cationic WPU, was also prepared. The thermal stability, glass transition temperature, and mechanical properties of the nanocomposites were investigated. The thermal stability of the WPU was enhanced with the incorporation of GO nanosheets. The glass transition temperature of the hard segment of WPU was increased by the incorporation of GO. These results are attributed the ne dispersion of GO in WPU and strong interfacial interactions between GO and WPU. Enhanced dispersion and interfacial interaction lead to better mechanical properties. Tensile strength, initial modulus, and elongation-at-break of WPU/GO nanocomposites were increased with the incorporation of GO nanosheets. By a simple method (anion-cation matching) we could prepare WPU/GO nanocomposites with enhanced stiffness and toughness.

Structures, properties and applications of the polyurethane ionomers

“…In the case of membrane with 30 wt% IL, ionic conductivity increased from the order of 10 -10 to the order of 10 -5 S cm -1 as temperature increased from -10 to 100°C [50]. The introduction of carbon nanotubes additionally increases the electrical conductivity of polyurethane coatings and independently contributes to the increase in thermal and mechanical properties, as demonstrated in few papers [13,46].…”

“…Tensile strength, initial modulus and elongation at break of WPU/GO nanocomposites were increased with the incorporation of GO nanosheets. WPU/GO nanocomposites with enhanced stiffness and toughness can be prepared by a simple method (anion-cation matching) [13].…”

Effect of a Monomer Composition on the Mechanical Properties and Glass Transition Temperature of a Waterborne Polyurethane/Graphene Oxide and Waterborne Polyurethane/MWCNT Nanocomposite

“…In all nanocomposites investigated, two transitions were observed: a distinct transition peak at higher temperature and a very weak shoulder at −40 °C. These temperatures were assigned to the glass transition temperature of the soft segment ( T gs ) and hard segment ( T gh ) [ 17 ]. T gh varied over a wide range and appeared at 0–60 °C depending on the composition and ionicity of the WPU, while T gs was independent of the composition and the iconicity and appeared at −40 °C.…”

“…Many studies in the literature have used rGO as a nanofiller to improve the electrical, mechanical, and barrier properties of WPU. rGO is still more expensive than multiwalled carbon nanotubes (MWCNTs), and dispersion of rGO in WPU is not easy [ 13 , 14 , 15 , 16 , 17 , 18 ]. Attempts to increase the electrical conductivity of WPU with GO or rGO have not been successful, and the improvement is inferior to that obtained with MWCNTs [ 13 , 14 ].…”

“…Without modification of the GO, a stable GO/anionic WPU dispersion cannot be obtained. Initially dispersed GO in WPU tends to reaggregate in several days [ 17 ].…”