Abstract
In an effort to expand the insulating behavior of adhesives, incorporated nano-sized fillers, such as multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs), are usually selected. Including both MWCNTs and GNPs into polymers is assumed to have complementary influence (synergy), providing a new research area. Nevertheless, limited studies have been carried out towards this hybrid direction, as it is challenging to achieve a uniform distribution of both fillers into the polymer matrix. In this work, the addition of MWCNTs and GNPs into the epoxy adhesives has been studied to increase their thermal and electrical conductivity without diminishing their mechanical properties. Three types of nano-reinforced adhesives were developed by using: 1) 2%wt. MWCNTs, 2) 8%wt. GNPs and 3) 1%wt. MWCNTs and 8%wt. GNPs. The production of nano-reinforced adhesives was achieved by using a three-roll milling technique, while during the experimental characterization single lap shear tests, thermal and electrical conductivity measurements were performed. According to the results, the introduction of nano-particles caused significant increases in electrical and thermal conductivity. MWCNTs in content of 2%wt. showed the highest improvement in the electrical conductivity (9 orders of magnitude), while GNPs in content of 8%wt. recorded the highest increase (207%) in the thermal conductivity of nano-reinforced adhesives. Finally, it was observed that the hybrid system successfully contributed to the development of a multi-functional epoxy adhesive with improved thermal and electrical properties without significantly compromising its mechanical properties.
Highlights
The design of an advanced structure has to meet certain requirements, such as efficiency, safety and reliability, which affect the complexity of the structure and the materials used in its construction
We study the influence of two types of carbon nanoparticles, Multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs), on mechanical, thermal, and electrical properties of epoxy adhesives
The electrical conductivity of the epoxy adhesive is increased by several orders of magnitude, when the conductive nano-fillers are introduced into the reference material
Summary
The design of an advanced structure has to meet certain requirements, such as efficiency, safety and reliability, which affect the complexity of the structure and the materials used in its construction. Suitable joining techniques, such as adhesive bonding, are required. The two basic joining methods are adhesive bonding and mechanical fastening such as bolting. Adhesive bonding does not require notches and loads are distributed over a larger surface than in mechanical joints. Adhesion is attracting interest in many industry fields, nowadays it is used commonly in aerospace, automotive, and electrical industries, civil and medical sectors due to its numerous advantages [2]. Epoxy adhesives are used to bond metal materials, composites, and concrete structures. In Aerospace industry, adhesive bonding helps to obtain lightweight structures, reduce stress concentration and corrosion. In recent years there is a tendency to convert insulating adhesives into electrically and thermally conductive materials without diminishing their initial properties [3]
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