Abstract
Nanocomposite coatings were successfully prepared by electrophoretic deposition of poly(etheretherketone) (PEEK)/graphene oxide (GO) suspensions. The GO flakes developed a large-scale co-continuous morphology with the basal plane mainly aligned with the coating surface. However, the PEEK particles were also found to be wrapped by GO nanosheets when deposited on the stainless steel substrate. Both phenomena, the co-continuous morphology and the wrapping effect, were dependent on the initial GO content in the suspension and influenced the final morphological characteristics of the thermally treated coatings. The PEEK matrix developed a dendritic morphology during its cooling from the molten state because of transcrystallinity that was induced by the incorporation of GO. The preparation of suspensions involved tip ultrasonication (TS) to deagglomerate, disperse, and mill the PEEK particles. A detailed study of the microstructure revealed that TS tended not only to reduce PEEK particle size, but also to promote an elongated shape, favourable for the nanocomposite coatings.
Highlights
Poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl1,4-phenylene) or poly(etheretherketone) (PEEK) is a high-performance and semicrystalline thermoplastic polymer in the polyaryletherketone family, which exhibits outstanding properties such as chemical, tribological, hard radiation and creep resistance as well as high strength and temperature stability, biocompatibility, low flammability without the necessity of flame-retardant additives, and low smoke emission [1,2,3,4,5]
The incorporation of graphene oxide (GO) has two main advantages: firstly, the adhesion of GO coatings on metallic substrates after thermal treatment has been attributed to the interaction between the oxygenated functional groups of GO and the metallic surface, and thereby, GO coatings have been used as the interface between PEEK and the metallic substrate to enhance the mechanical properties [21]; secondly, p-conjugated structures in graphitic materials can form strong p–p stacking interactions with the benzene ring such that found in PEEK [22, 23]
The results indicate that GO has an important role in the micromorphology of the coatings, as GO nanosheets develop a large-scale co-continuous morphology characterised by the basal plane of the nanosheets mainly aligned with the coating surface, and the wrapping of PEEK particles by GO nanosheets
Summary
Poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl1,4-phenylene) or poly(etheretherketone) (PEEK) is a high-performance and semicrystalline thermoplastic polymer in the polyaryletherketone family, which exhibits outstanding properties such as chemical, tribological, hard radiation and creep resistance as well as high strength and temperature stability, biocompatibility, low flammability without the necessity of flame-retardant additives, and low smoke emission [1,2,3,4,5]. Nanocomposite performance depends on different factors such as dispersion, matrix–filler interactions, and, in case of flake and fibre reinforcements, alignment [10] In this respect, EPD is useful to develop specific microstructures from multicomponent suspensions [14]; for instance, in the study of PEEK/MoS2 coatings by electrophoretic codeposition, MoS2 was found to align preferentially, parallel to the coating surface [15]. The incorporation of GO has two main advantages: firstly, the adhesion of GO coatings on metallic substrates after thermal treatment has been attributed to the interaction between the oxygenated functional groups of GO and the metallic surface, and thereby, GO coatings have been used as the interface between PEEK and the metallic substrate to enhance the mechanical properties [21]; secondly, p-conjugated structures in graphitic materials can form strong p–p stacking interactions with the benzene ring such that found in PEEK [22, 23]. Because of its structural characteristics and outstanding properties, GO has been implemented as filler in the development of numerous polymer matrix nanocomposite systems for several applications [27,28,29,30,31]
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