Effect of Expanded Graphite on Mechanical and Tribological Properties of Polyamide 6/Glass Fibre Composites

Dajana Japić,Miroslav Huskić,Blaž Nardin,Simon Kulovec,Janez Slapnik,Mitjan Kalin,Behnam Ghalei

doi:10.1155/2022/9974889

Dajana Japić, Miroslav Huskić + Show 5 more

Open Access

https://doi.org/10.1155/2022/9974889

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Abstract

The quality of plastic gears, especially their durability, is becoming increasingly important due to advances in electric mobility. Therefore, new materials are being developed that must have better mechanical properties, high thermal conductivity for heat dissipation, and tribological properties. The composites of expanded graphite (EG) and glass fibre-reinforced polyamide 6 (PA6/GF) were prepared, and the effect of EG particle size (~5 μm (EG5) and ~1000 μm (EG1000)) on these properties was investigated. Composites with different contents (2-10 wt%) of EG in PA6/GF were prepared using a laboratory twin-screw extruder and then injection moulded in the form of rods and discs required for thermal, thermomechanical, and tribological tests. EG acted as a nucleating agent but hindered the crystallization rate at higher concentrations, which was more pronounced when EG5 was added. Dynamic mechanical analysis showed that the storage modulus increased with the addition of both types of EG. However, the addition of EG5 increased the storage modulus more than EG1000. The lowest coefficient of friction was obtained by the addition of 10 wt% EG5. The wear increased with the addition of both types of EG, only slightly with the addition of EG1000. The thermal conductivity of the composites with EG increased from 0.42 W/mK to 1 W/mK. The results show that the use of EG with smaller particle size is much more beneficial than with a larger one.

Highlights

Polymers are used in various applications where the durability of the product depends heavily on the mechanical as well as on the tribological properties of polymers
Suresha et al reported that graphite reduced the coefficient of friction (COF) and wear rate and improved the thermal conductivity and mechanical properties of epoxy composites [12]
The Scherrer equation was used to calculate the crystallite sizes of the graphites, which are 25.7 nm and 20.3 nm for EG1000 and EG5, respectively

Summary

Introduction

Polymers are used in various applications where the durability of the product depends heavily on the mechanical as well as on the tribological properties of polymers. Electrical, and tribological properties of polymers, various graphite powders are widely used as fillers [6, 7]. Various types of graphite, such as natural, synthetic, expanded (EG), or expandable graphite, are often added to polymers to improve thermal and electrical conductivity as well as mechanical and tribological properties. Suresha et al reported that graphite reduced the coefficient of friction (COF) and wear rate and improved the thermal conductivity and mechanical properties of epoxy composites [12]. The results show that the influence of the composite preparation method on tribological properties cannot be neglected. The addition of graphite decreased the COF but increased the wear rate [14]. The graphite particle size played an important role against steel, but not against PA66 [15]

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