Functionalised-nanodiamond on textiles for versatile applications

Introducing nanomaterials (NMs) to a fibrous substrate has expanded the application of textiles to various fields such as construction, medical, protection, and energy. These promising outcomes are the driving forces for researchers to explore various aspects, including introducing a different class of NMs, their application through numerous approaches and various novel properties that can potentially be achieved. A diamond nanoparticle is a biocompatible material with extraordinary thermal, mechanical, chemical and optical properties. Nanodiamond (ND) has been extensively studied for its composite with polymers, showing promising results such as improved thermal conductivity, mechanical strength and corrosion properties. Recently, ND has been adopted to combine with fibrous materials in nanofibres, filaments, yarns and fabrics, which opened a new potential application area for ND. However, since ND is a relatively new material to the textile industry, research and knowledge in this area are very limited. The main challenges in applying ND to textiles include its uneven distribution in a fibrous system, the expected performance of the nanocomposite, the application areas, the poor durability, the poor reliability of the performance, and the compromised comfort of the prototypes. Therefore, this PhD project aims to develop ND/fibre composites with durability for some potential applications. Three various chemical approaches were adopted to apply ND to fabric, and each set of samples was then assessed for a specific application. To fulfil the aim of the research, it is required to gain an in-depth knowledge of ND and its composite with various materials including polymers, metals and fibres. Therefore, a literature review was conducted to understand ND structure, surface functionalisation, synthesis techniques and applications. Furthermore, its amalgamation techniques, properties, and application areas with various materials have been reviewed. As a result, it has been found that ND has the potential for application in the fibrous system; however, challenges exist in terms of limited knowledge about their manufacturing techniques, chemistry, durability and application areas. The first approach adopted to apply ND to fibres was in-situ polymerisation with polyaniline (PANI). Aniline was selected to achieve conductivity along with ND properties. Composites of wool fabrics with ND and PANI were further applied as strain sensors. The nanocomposite fabrics with PANI-ND demonstrated high sensitivity, enhanced durability, and mechanical properties without compromising the inherent properties of textiles, such as comfort and breathability. This work provides insights into developing highly sensitive multifunctional electronic textiles (such as wearable sensors). A potential application for ND/fibre composites is cooling textiles, as ND can increase the thermal conductivity of insulation textile fibres, promoting heat dissipation. Engineering textiles with cooling performance while maintaining their intrinsic traits, e.g., lightweight, washable, comfortable and durable, is a great challenge in developing personal cooling garments. The approach employed to integrate ND into fabrics was through templating of polydopamine (PDA) followed by the application of ND with different functionalised groups. Due to the excellent thermal conductivity of ND, the temperature difference between the coated and uncoated fabrics was high within a short time span of 30 min, showing that the ND-coated fabric could be used for personal comfort during summer. In addition, the coated ND-PDA-Wool fabrics demonstrated enhanced thermal stability and mechanical properties with excellent durability, and the water absorbency was greatly enhanced with well-maintained air permeability. The idea of generating cooling textiles through ND was successful but it has some drawbacks including a lengthy process, undesirable black color, limited sample size and wastage of ND. Therefore, direct application of ND onto one side of fabric was adopted through electrospraying ND and thermoplastic polyurethane (TPU). The thermal resistance was measured by a sweating guarded hot plate (SGHP), which confirmed lower thermal resistance of fabric from the skin to the atmosphere as compared to control and thermal resistance from the atmosphere to the skin was same for both controlled and treated samples. Similarly, thermal conductivity, radiant heat transfer and infrared spectroscopy characterizations strengthened the findings of SGHP results. Real-life simulated experiments were also conducted to verify the performance of developed samples. The electrosprayed samples also showed higher ultraviolet protection than the control sample. The coating did not affect the air permeability and water absorbency of pristine cotton fabrics. It was found that NDs when placed onto the skin side of the fabrics promoted heat dissipation towards the atmosphere while the other side of the fabric, exposed to the hot atmosphere, remains uncoated to delay the transfer of human body heat to the environment due to higher thermal resistance.