Influence of Surface Modified Nanodiamonds on Dielectric and Mechanical Properties of Silicone Composites.

Alexandra Shakun,Rafal Anyszka,Essi Sarlin,Jyrki Vuorinen,Anke Blume

doi:10.3390/polym11071104

Alexandra Shakun, Rafal Anyszka + Show 3 more

Open Access

https://doi.org/10.3390/polym11071104

Copy DOI

Abstract

Detonation nanodiamonds, also known as ultradispersed diamonds, possess versatile chemically active surfaces, which can be adjusted to improve their interaction with elastomers. Such improvements can result in decreased dielectric and viscous losses of the composites without compromising other in-rubber properties, thus making the composites suitable for new demanding applications, such as energy harvesting. However, in most cases, surface modification of nanodiamonds requires the use of strong chemicals and high temperatures. The present study offers a less time-consuming functionalization method at 40 °C via reaction between the epoxy-rings of the modifier and carboxylic groups at the nanodiamond surface. This allows decorating the nanodiamond surface with chemical groups that are able to participate in the crosslinking reaction, thus creating strong interaction between filler and elastomer. Addition of 0.1 phr (parts per hundred rubber) of modified nanodiamonds into the silicone matrix results in about fivefold decreased electric losses at 1 Hz due to a reduced conductivity. Moreover, the mechanical hysteresis loss is reduced more than 50% and dynamic loss tangent at ambient temperature is lowered. Therefore, such materials are recommended for the dielectric energy harvesting application, and they are expected to increase its efficiency.

Highlights

Detonation-produced nanodiamonds (NDs), named ultradispersed diamonds (UDDs), are known for their superior mechanical properties, low electrical conductivity, high thermal conductivity and a highly reactive surface
The present study indicates that the application of surface-modified NDs can be beneficial for the dielectric energy harvesting application and could potentially increase the efficiency of dielectric energy generators
Carboxylated nanodiamonds were successfully modified with modifying agents containing epoxy-groups

Summary

Introduction

Detonation-produced nanodiamonds (NDs), named ultradispersed diamonds (UDDs), are known for their superior mechanical properties, low electrical conductivity, high thermal conductivity and a highly reactive surface. Single ND particles are about 5 nm in diameter consisting of a sp3 -carbon core, less than 1 nm thick sp2 –carbon transitional layer and an active surface [1]. The surface of a pristine ND is hydrophilic and mostly contains carboxyls, hydroxyls, lactones, ketones and ethers, but it can be modified and homogenized through a large number of methods [2]. Due to the presence of carboxyl- and hydroxyl- groups, NDs form strong aggregates and agglomerates, which are difficult to break down, affecting the dispersability of NDs. Further surface modification allows introducing complex moieties onto the ND surface and could decrease interactions between the ND particles. NDs have shown an ability to reduce dielectric losses in Polymers 2019, 11, 1104; doi:10.3390/polym11071104 www.mdpi.com/journal/polymers

Objectives

Results

Conclusion