Material Extrusion of Wool Waste/Polycaprolactone with Improved Tensile Strength and Biodegradation.

Additive manufacturing (AM) through material extrusion (MEX) is becoming increasingly popular worldwide due to its simple, sustainable and safe technique of material preparation, with minimal waste generation. This user-friendly technique is currently extensively used in diverse industries and household applications. Recently, there has been increasing attention on polycaprolactone (PCL)-based composites in MEX due to their improved biodegradability. These composites can be printed at a lower temperature, making them more energy efficient compared to commercial filaments such as acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA). Although wool is the leading protein fibre in the world and can be more compatible with PCL due to its inherent hydrophobicity, the suitability of MEX using a wool/PCL combination has not been reported previously. In the current study, waste wool/PCL composite parts were printed using the MEX technique, and rheology, thermal and tensile properties, and morphology were analysed. The impact of wool loading (10% and 20%) was investigated in relation to different filling patterns (concentric, rectilinear and gyroid). Furthermore, the impact of fibre fineness on the final material produced through MEX was investigated for the first time using two types of wool fibres with diameters of 16 µm and 24 µm. The yield strength and modulus of PCL increased with the inclusion of 10% wool, although the elongation was reduced. The crystallinity of the composites was found to be reduced with wool inclusion, though the melting point of PCL remained mostly unchanged with 10% wool inclusion, indicating better compatibility. Good miscibility and uniform structure were observed with the inclusion of 10% wool, as evidenced by rheology and morphology analysis. The impact of fibre fineness was mostly minor, though wool/PCL composites showed improved thermal stability with finer diameter of wool fibres. The printed specimens exhibited an increasing rate of biodegradation in marine water, which was correlated to the amount of wool present. Overall, the results demonstrate the practical applicability of the wool/PCL composition in MEX for the preparation of varied objects, such as containers, toys and other household and industrial items. Using wool/PCL combinations as regular plastics would provide a significant environmental advantage over the non-degradable polymers that are currently used for these purposes.

Sustainable Cotton Gin Waste/Polycaprolactone Bio-Plastic with Adjustable Biodegradation Rate: Scale-Up Production through Compression Moulding.

Cotton gin trash (CGT), a lignocellulosic waste generated during cotton fibre processing, has recently received significant attention for production of composite bio-plastics. However, earlier studies were limited to either with biodegradable polymers, through small-scale solution-casting method, or using industrially adaptable extrusion route, but with non-biodegradable polymers. In this study, a scale-up production of completely biodegradable CGT composite plastic film with adjustable biodegradation rate is proposed. First using a twin screw extruder, the prepared CGT powder was combined with polycaprolactone (PCL) to form pellets, and then using the compressing moulding, the pellets were transformed into bio-plastic composite films. Hydrophilic polyethylene glycol (PEG) was used as a plasticiser in the mixture and its impact on the biodegradation rate was analysed. The morphology of CGT bio-plastic composite films showed even distribution of CGT powder within the PCL matrix. The CGT incorporation improved the UV resistance, thermal stability, and Young's modulus of PCL material. Further, the flexibility and mixing properties of the composites were improved by PEG. Overall, this study demonstrated a sustainable production method of CGT bio-plastic films using the whole CGT and without any waste residue produced, where the degradation of the produced composite films can be adjusted to minimise the environmental impact.

Biodegradable UV-Protective Composite Film from Cellulosic Waste: Utilisation of Cotton Gin Motes as Biocomponent.

With an increase in environmental pollution and microplastic problems, it is more urgent now to replace non-biodegradable films with biodegradable films that are low-cost and from renewable resources. Cotton gin motes (GM), a type of cellulosic waste that is generated from cotton ginning, is an excellent candidate for fabricating biodegradable films due to its properties and abundance. In this study, GM was first mechanically milled into a fine powder, followed by compounding with polycaprolactone (PCL) and extruded to produce composite pellets which were then compress-moulded into composite films. This environmentally friendly process used physical processing and all the materials were consumed in the process without generating any waste residue. To improve the compatibility and mixing properties between GM and PCL, the use of a plasticiser (polyethylene glycol) was considered. A high content of GM powder (up to 50%) was successfully compounded with the polymer. The SEM images of the composite films showed smooth surface morphology and well-distributed GM powder in the PCL matrix. The added advantage of compounding GM with the polymer matrix was that the composite film developed UV-shielding properties due to the presence of lignin in the GM powder. This property will be critical for films used in UV-resistance applications. Furthermore, the composite even with high GM content (50%), showed good mechanical properties, with 9.5 MPa yield strength and 442% elongation, which was only a 50% decrease in elongation when compared with clear PCL film. The soil biodegradation of GM composite films under controlled temperature (20 °C) and humidity (50%) for 1 month showed around 41% weight loss. Overall, this study demonstrates the potential of GM to be used as a biodegradable and UV-protective composite film for a wide array of applications, such as packaging and UV-protective coverings.

Comparative Preparation Method and Associated Cost of Lignin-Cellulose Nanocrystals.

Lignin is a natural source of UV-shielding materials, though its recalcitrant and heterogeneous structure makes the extraction and purification processes complex. However, lignin's functionality can be directly utilised when it stays as native with cellulose and hemicellulose in plant biomass, rather than being separated. The fabrication process of this native lignin is sustainable, as it consumes less energy and chemicals compared to purified lignin; thus, it is an economic and more straightforward approach. In this study, the properties of native and purified lignin-cellulose nanocrystals (L-CNCs) sourced from hemp hurd waste were compared to explore the differences in their morphology, UV-shielding properties and chemical structure affected by their distinct fabrication process. These two kinds of L-CNCs were further added into polyvinyl alcohol (PVA) to evaluate their reinforcement characteristics. The resulting native L-CNCs/PVA film showed stronger UV-shielding ability than purified L-CNCs. Moreover, the native L-CNCs showed better compatibility with PVA, while the purified L-CNCs/PVA interfaces showed phase separation. The phase separation in purified L-CNCs/PVA films reduced the films' tensile strength and Young's modulus and increased the water vapour transmission. The laboratory-scale cost of native L-CNCs production (~AUD 80/kg) was only 10% of purified L-CNCs (~AUD 850/kg), resulting in a comparatively lower cost for preparing native L-CNCs/PVA composite films. Overall, this study shows that the proposed method of production and use of native L-CNCs can be an economic approach to deliver UV-shielding properties for potential applications, such as food packaging.

Sustainable biodegradable denim waste composites for potential single-use packaging.

Every year a massive 2.16 million metric tons of denim jeans is globally wasted and mostly goes into landfill. Though denim is highly rich in cellulose, its valorisation has received little attention. A few attempts have previously shown prospects of denim in composites, though the ultimate products were non-compostable due to the nature of the chosen matrix. This research proposes a novel development of denim/cornstarch composite, maintaining 50/50 fractions, using different denim snippet size. A smoother denim/cornstarch composite morphology and higher tensile strength were observed when smaller denim snippets were used, whereas larger snippets produced voids and roughness and a higher hygroscopicity. Composite prepared from semi-gelatinised cornstarch showed a completely flexible structure similar to non-woven sheet. The chemical structure was observed identical in all of the composites and a good structural compatibility perceived. Individual peaks of both denim (1105 cm-1 and 1705 cm-1) and cornstarch (1081 cm-1) were confirmed in all composite samples, either gelatinised or semi-gelatinised cornstarch used. Overall, this work reveals an eco-friendly approach to utilise consumed denim waste, with insight on possible fine-tuning through alteration of denim snippet size and cornstarch gelatinisation. The mechanical and moisture properties of the composites also suggest their potential application in single-use packaging.

Lignin-Cellulose Nanocrystals from Hemp Hurd as Light-Coloured Ultraviolet (UV) Functional Filler for Enhanced Performance of Polyvinyl Alcohol Nanocomposite Films.

Lignin is a natural light-coloured ultraviolet (UV) absorber; however, conventional extraction processes usually darken its colour and could be detrimental to its UV-shielding ability. In this study, a sustainable way of fabricating lignin-cellulose nanocrystals (L-CNCs) from hemp hurd is proposed. A homogeneous morphology of the hemp particles was achieved by ball milling, and L-CNCs with high aspect ratio were obtained through mild acid hydrolysis on the ball-milled particles. The L-CNCs were used as filler in polyvinyl alcohol (PVA) film, which produced a light-coloured nanocomposite film with high UV-shielding ability and enhanced tensile properties: the absorption of UV at wavelength of 400 nm and transparency in the visible-light region at wavelength of 550 nm was 116 times and 70% higher than that of pure PVA, respectively. In addition to these advantages, the nanocomposite film showed a water vapour transmission property comparable with commercial food package film, indicating potential applications.

A Facile Approach of Fabricating Electrically Conductive Knitted Fabrics Using Graphene Oxide and Textile-Based Waste Material.

This research investigated a feasible approach to fabricating electrically conductive knitted fabrics using previously wet-spun wool/polyacrylonitrile (PAN) composite fibre. In the production of the composite fibre, waste wool fibres and PAN were used, whereby both the control PAN (100% PAN) and wool/PAN composite fibres (25% wool) were knitted into fabrics. The knitted fabrics were coated with graphene oxide (GO) using the brushing and drying technique and then chemically reduced using hydrazine to introduce the electrical conductivity. The morphological study showed the presence of GO sheets wrinkles on the coated fabrics and their absence on reduced fabrics, which supports successful coating and a reduction of GO. This was further confirmed by the colour change properties of the fabrics. The colour strength (K/S) of the reduced control PAN and wool/PAN fabrics increased by ~410% and ~270%, and the lightness (L*) decreased ~65% and ~71%, respectively, compared to their pristine fabrics. The Fourier transform infrared spectroscopy showed the presence and absence of the GO functional groups along with the PAN and amide groups in the GO-coated and reduced fabrics. Similarly, the X-ray diffraction analysis exhibited a typical 2θ peak at 10° that represents the existence of GO, which was demolished after the reduction process. Moreover, the wool/PAN/reduced GO knitted fabrics showed higher electrical conductivity (~1.67 S/cm) compared to the control PAN/reduced GO knitted fabrics (~0.35 S/cm). This study shows the potential of fabricating electrically conductive fabrics using waste wool fibres and graphene that can be used in different application fields.

Sustainable Lightweight Insulation Materials from Textile-Based Waste for the Automobile Industry.

Globally, automotive manufacturers are looking for ways to produce environmentally sustainable and recyclable materials for automobiles to meet new regulations and customer desires. To enable the needs for rapid response, this study investigated the feasibility of using waste and virgin wool fibres as cost-effective and sustainable alternatives for automotive sound and heat insulation using a chemical-free approach. Several properties of the currently available commercial automotive insulators were investigated in order to facilitate the designing of green wool-based needle-punched nonwoven materials. The effect of fibre diameter, nonwoven surface, layer structure, thickness, and area density on sound absorption and thermal resistance was investigated. The results suggested that the wool nonwoven materials, fabricated using waste and virgin wool fibres, possessed extremely efficient acoustic and thermal insulating properties comparable with the currently used commercial synthetic insulating materials. Besides, the wool nonwoven materials showed identical antibacterial and antifungal properties with a greater biodegradation rate (50%) than that of the commercial synthetic insulating materials. Hence, this study showed that natural wool fibres have the potential to be used as green, lightweight, and sustainable materials in the automobiles, while they qualify for Reuse-Recycle and Reuse-Recover purposes at the end-of-life of vehicles.

Graphene oxide incorporated waste wool/PAN hybrid fibres.

This work aims to evaluate the potential of using textile waste in smart textile applications in the form of a hybrid fibre with electrical properties. The bio-based electrically conductive fibres were fabricated from waste wool and polyacrylonitrile (PAN) via wet spinning with different wool content. The control PAN and hybrid fibre produced with the highest amount of wool content (25% w/v) were coated with graphene oxide (GO) using the "brushing and drying" technique. The GO nanosheets coated control PAN and wool/PAN hybrid fibres were chemically reduced through hydrazine vapour exposure. The Fourier transform infrared spectroscopy showed the presence of both protein and nitrile peaks in the wool/PAN hybrid fibres, although the amide I and amide A groups had disappeared, due to the dissolution of wool. The morphological and structural analysis revealed effective coating and reduction of the fibres through GO nanosheets and hydrazine, respectively. The hybrid fibre showed higher electrical conductivity (~ 180 S/cm) compared to the control PAN fibres (~ 95 S/cm), confirming an effective bonding between the hydroxyl and carboxylic groups of the GO sheets and the amino groups of wool evidenced by chemical analysis. Hence, the graphene oxide incorporated wool/PAN hybrid fibres may provide a promising solution for eco-friendly smart textile applications.

A Review on the Production Methods and Applications of Graphene-Based Materials.

Graphene-based materials in the form of fibres, fabrics, films, and composite materials are the most widely investigated research domains because of their remarkable physicochemical and thermomechanical properties. In this era of scientific advancement, graphene has built the foundation of a new horizon of possibilities and received tremendous research focus in several application areas such as aerospace, energy, transportation, healthcare, agriculture, wastewater management, and wearable technology. Although graphene has been found to provide exceptional results in every application field, a massive proportion of research is still underway to configure required parameters to ensure the best possible outcomes from graphene-based materials. Until now, several review articles have been published to summarise the excellence of graphene and its derivatives, which focused mainly on a single application area of graphene. However, no single review is found to comprehensively study most used fabrication processes of graphene-based materials including their diversified and potential application areas. To address this genuine gap and ensure wider support for the upcoming research and investigations of this excellent material, this review aims to provide a snapshot of most used fabrication methods of graphene-based materials in the form of pure and composite fibres, graphene-based composite materials conjugated with polymers, and fibres. This study also provides a clear perspective of large-scale production feasibility and application areas of graphene-based materials in all forms.

Transparent Ultraviolet (UV)-Shielding Films Made from Waste Hemp Hurd and Polyvinyl Alcohol (PVA).

This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively influences the transparency of the resulting composite. High transparency and UV-shielding are desirable properties for many applications. In this study, composites were made by mixing lignocellulose particles and polyvinyl alcohol (PVA), where lignocellulose particles were obtained from ball-milled waste hemp hurd without chemical treatments. The UV-shielding properties of the resulting composite film, as a function of hemp/PVA weight ratios, were investigated. The intermolecular interactions between the hemp particles and the PVA were characterized using infrared spectroscopy with the presence of -C=O group at 1655 cm-1, providing evidence that the chemical structure of lignin was preserved. The fabricated hemp/PVA films exhibit stronger UV-shielding, in the UVA-I range (340-400 nm) than TiO2/PVA films. The composite films also showed comparable water vapor permeability (WVP) with commercial packaging plastic film made of HDPE (high-density polyethylene). The optimization experiments were reported, with aim at understanding the balance between the UV-shielding and mechanical properties of the hemp/PVA films. The findings of this work can be applicable to the packaging, food and cosmetic industries where UV shielding is of utmost importance, hence adding value to hemp hurd waste.

Advanced Functional Fibrous Materials for Enhanced Thermoregulating Performance.

The concept of thermoregulating textiles capable of providing personal thermal management property (PTM) has attracted significant attention in recent years. It is considered as an emerging approach to promote the comfort and general well-being of wearers and also to mitigate the energy consumption load for indoor living space conditioning. Regulating the heat exchange between human body and environment has been the core subject of many studies on introducing the PTM functionality to textiles. This work provides an overview of the latest literature, summarizing the recent innovations and state-of-the-art approaches of controlling the heat gain and loss of textiles. To this end, methods to control the fundamental aspects of heat gain and loss of fabrics such as using near-infrared reflective materials and conductive nanomaterials, designing photonic structures of fabrics, and engineering nanoporous structures for passive cooling and heating effects will be discussed. Moreover, specific attention is given to the application of phase change materials in textiles, their integration methods, and the associated mechanisms. Several commercial methods such as adapting the innovative designs, introducing moisture management capability, and using air/liquid thermoregulating systems will also be discussed. This review article provides a clear picture of the concept of thermoregulating textiles and recommends some future research trajectories for this emerging field.

Fabrication of a cost-effective lemongrass (Cymbopogon citratus) membrane with antibacterial activity for dye removal.

Dye wastewater has attracted much attention due to its severe environmental and health problems. The main challenge of separating dyes from wastewater, using adsorption, is developing a functional adsorbent that is cost-effective and sustainable. In this work, we have fabricated a novel low-cost membrane with antibacterial properties from naturally sustainable lemongrass (LG). Lemongrass was cut and milled into powder, then dissolved to prepare a lemongrass membrane. Graphene oxide (GO) was also included to prepare a LG/GO composite membrane. The physiochemical and antibacterial properties of membranes were evaluated and their dye adsorption capability was examined using methylene blue (MB) dye at different concentrations. The kinetic study revealed that the MB adsorption process complied with the pseudo second-order model. The lemongrass membrane showed a rough surface morphology, high reduced modulus and hardness, yet comparable dye adsorption to the LG/GO composite membrane. Considering the natural sustainability of lemongrass as an abundant cellulosic resource, its excellent dye adsorption, antibacterial properties and low cost as well as the facile fabrication technology, the lemongrass membrane could be a promising candidate for dye removal from wastewater with easy separation after use.