Graphene Materials Strengthen Aqueous Polyurethane Adhesives

Abstract

Carboxyl-functionalized graphene platelets (GP) and graphene oxide (GO) sheets were added to a commercial aqueous adhesive dispersion of thermoplastic polyurethane (TP) (Idrotex 200 from FacGB s.r.l.). For both additives, the weight percentage was of industrial interest, 0.01 and 0.1 wt %. The addition of GP/GO was carried out in a simple and scalable-up process that can be applied to other materials and additives. Mechanical, peel tests were applied on polyurethane strips (75 mm long, 15 mm wide, and 1.5 mm thick) prepared cutting extruded sheets obtained using Estane 58091, a 70D aromatic polyester-based TP. The tests with 0.01 wt % of GP showed statistically significant higher forces at first failure and maximum forces with respect to the pristine adhesive. Sample characterization was carried out with scanning electron microscopy, infrared spectroscopy, X-ray diffraction, and thermal analysis. A mechanism is suggested for the improved performance of the low-dose GP adhesive.

Addition of Graphene Oxide in Different Stages of the Synthesis of Waterborne Polyurethane-Urea Adhesives and Its Influence on Their Structure, Thermal, Viscoelastic and Adhesion Properties

“…The bands due to the hard segments appear at 3367 cm −1 (N-H stretching), 1727 cm −1 (C=O stretching), and 1532 cm −1 (C-N stretching); the bands of the soft segments correspond to C-H stretching at 2873 and 2952 cm −1 , CH 2 bending at 1461 cm −1 , and several C-O bands of the polyester polyol at 1239, 1140, 1166, 1065 and 958 and 735 cm −1 . The addition of 0.04 wt % GO does not produce new bands in the ATR-IR spectra of the PU films but some changes of the wavenumber of some absorption bands are observed, these changes can be associated to a structural reorganization [ 35 ]. Thus, the N-H band at 3367 cm −1 in the PU film without GO is displaced to 3354 cm −1 in PU+0.04 wt % GO in polyol, indicating the existence of interactions between the functional groups on the GO sheets and the hard segments of the polyurethane-urea ( Figure 6 a).…”

“…To the best of our knowledge, the addition of graphene derivative for improving the adhesion of polyurethane adhesives has been only considered by Cristofolini et al [35]. These authors prepared 0.01 wt % carboxyl-functionalized graphene platelets (GP) and 0.1 wt % GO blends that were added to very diluted in water (1 wt %) commercial waterborne polyurethane dispersion, after which an increase in the peel strength was obtained.…”

Addition of small amounts of graphene oxide in the polyol during the synthesis of waterborne polyurethane urea adhesives for improving their adhesion properties

“…Kale et al [38] mixed a commercial waterborne polyurethane with 0.2 wt% graphene oxide and silica intended for leather coatings and improved mechanical and thermal properties, flexibility and adhesion to leather were obtained, the enhanced adhesion was ascribed to improved interfacial interactions. On the other hand, Cristofolini et al [39] have added 0.01 wt% carboxyl-functionalized graphene platelets (GP) and 0.1-1 wt% GO blends to commercial waterborne polyurethane dispersions by vigorous mixing and their adhesion properties have been assessed, the addition of 0.01 wt% GP increased the peel strength.…”

Influence of the Surface Chemistry of Graphene Oxide on the Structure–Property Relationship of Waterborne Poly(urethane urea) Adhesive

“…Kale et al [ 22 ] added epoxy functionalized GO and amine functionalized nanosilica to PUD by physical mixing, resulting in the improvement of the mechanical, thermal, and adhesion to leather properties. Cristofolini et al [ 23 ] added 0.01 wt.% carboxyl-functionalized graphene nano-platelets (GP) + 0.1–1 wt.% GO to commercial PUD by vigorous mixing for increasing the adhesion properties, the addition of 0.01 wt.% GP increased the adhesive strength. Tounici and Martín-Martínez [ 24 , 25 ] added 0.01 to 0.10 wt.% GO during the synthesis of PUDs, and improved adhesive strength was obtained by adding 0.04 wt.% GO.…”