Experimental assessment on the mechanical, physical, thermal, and chemical properties of halloysite and carbon nanoparticles reinforced epoxy resins for repair applications

Halloysite nanotubes (HNT) and carbon nanotubes (CNT) are potential nanoparticles that can be incorporated into polymer adhesives to enhance their performance for repairing damaged composite structures. However, the nanoparticle adhesive blends need to be assessed as their performance may be affected by the preparation techniques, nanoparticles types, and mass concentration. The present study aimed to evaluate the mechanical properties (specifically tensile and adhesion properties), physical properties (including wetting and rheological characteristics), thermal properties, and chemical properties of two commercially available adhesives, namely Epo-Tek 301 (consists of bisphenol A diglycidyl ether resin, known as DGEBA) and Nano-Force E100 (consists of bisphenol A/F epichlorohydrin premixed with CNTs). Furthermore, DGEBA adhesive with 1, 3, 5, and 9 wt% HNTs, and DGEBA adhesive with 1 wt% of treated and untreated CNTs were prepared. The findings revealed that there were no appreciable differences in the mechanical, physical, thermal, and chemical properties between the neat DGEBA and DGEBA with 1 wt% HNTs. However, the mechanical and physical properties deteriorated, and the char yield increased after thermal degradation for adhesives containing more than 1 wt% HNTs. On the other hand, no enhancement in all properties was observed for adhesives containing CNTs. Moreover, the adhesives containing CNTs exhibited higher viscosity than Nano-Force E100, which could hinder resin infiltration for composite repair applications. Therefore, the types of adhesive to be used for repairing impact-damaged composite structures must be prudently selected.