Addition of graphite nanoplatelets (GN) increased the extent of cross-linking and degree of curing of the vinylester (VE) resin when cured at 25°C mainly because of the hydrogen bond formation between the carbon-oxygen species on the GN surface and the OH and C=O groups of the VE monomer, anchoring the VE monomer on the GN surface favouring the polymerization on the nanoplatelets surface. The GN particles were well dispersed into the VE matrix and good interfacial interaction was observed. The more extended curing caused by adding GN was evidenced by an increase in the glass transition temperature. On the other hand, the relaxation at 90°C of the VE polymer cured at 25°C due to uncompleted cross-linking was displaced to lower temperature (75°C) when 0.1-lwt% GN was added. When the VE resin was cured at 25°C, the addition of GN restrained the deformation of the polymeric matrix causing an increase in tensile strength; however, when the cure is produced at 100°C the increase in the GN content had negligible effect in the mechanical properties of the polymer. Finally, the addition of 0.1 wt% GN only increases the shear strength of cold-rolled steel/VE adhesive joints in more than 2MPa, and the adhesive strength increases noticeably by increasing the GN content particularly when the cure was produced at 25°C.
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