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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. [ABSTRACT FROM AUTHOR]

The application of plasma on textiles is a highly beneficial technique to improve dyeability and reduce the consumption of water, energy, and time. This is advantageous for the industries to demonstrate high productivity and quality of the product but at a lower cost. Plasma treatment usually is applied as a pre-treatment before the conventional dyeing process, where the generation of dye wastewater remains a challenge. Plasma post-treatment can make a huge difference in reducing the dye wastewater; however, this has received little attention and more specifically the effectiveness of plasma on natural dye fixation is unknown. Natural dyes from waste, such as onion skin (Allium cepa L.) are greatly abundant and a low-cost green option for sustainable dyeing of textiles. In this study, a clean method of dyeing wool fabric with onion skin is proposed using a plasma-assisted spray-dyeing technique with no wastewater discharge. Four different plasma parameters were used varying the plasma operating power (40 W and 64 W) and treatment duration (30 s and 60 s). Mordanting and dyeing were done by a successive spraying-drying method in multiple rounds to reach the identical shade of a parallelly conducted conventional dyeing process. The removal of the cuticle layer of wool by plasma treatment was perceived from the morphology of the treated fabric, possibly contributing to the wettability. A higher plasma operating power and longer treatment time were beneficial and affected the overall dyeability. The chemical structure of wool showed a higher hydroxyl peak intensity after dyeing and a lower peak intensity of C–H groups after plasma post-treatment. The colour fastness properties (washing and crocking) improved after plasma post-treatment and confirmed the possible attachment of unfixed dyes with fabric. Overall, the time and energy consumed by the plasma-assisted spray-dyeing technique was nearly one-third of conventional dyeing, with no wastewater generation and led to a better colour strength (20.4 compared to 15.8) and similar colour fastness. Results showed the great potential for this newly proposed method as a sustainable textile dyeing alternative. [Display omitted] • First ever use of plasma post-treatment for fixation of natural dye on wool fabric. • Plasma-assisted spray-dyeing technique is proposed with no wastewater discharge. • Similar colour strength and fastness achieved compared to conventional dyeing. • One-third of time and energy consumed compared with conventional dyeing. [ABSTRACT FROM AUTHOR]

3D printing is a popular technique for numerous applications from households to industrial purposes. Commercially available filaments for 3D printing are not eco-friendly, yet energy intensive due to their high extrusion temperature (200–220°C). Polycaprolactone (PCL) is increasingly proposed for 3D printing due to its biocompatibility and lower extrusion temperature, which is more sustainable, though is slow in actual biodegradation. Although PCL-blends are often proposed to promote the degradation, strong hydrophobicity of PCL leads to poor compatibility. This study, for the first time proposes waste wool/PCL filaments for 3D printing using a clean production method, to utilise the hydrophobicity of wool as an advantage with PCL interfaces. Micro-sized wool powders from waste wool fabrics of two fibre fineness (16 and 24 μm) were prepared with minimal in-process waste and then extruded completely with PCL using different ratios (10/90, 20/80 and 25/75 combination of wool/PCL) to produce the composite filaments. A uniform mixing in the composite structure was observed particularly with 10% of wool loading, also the biodegradation rate significantly increased, i.e., from 0.8% to 6.8–10.5% in 3 months. Filaments prepared with 10% and 20% wool showed an increased yield strength, while a finer diameter of initial fibre was found more influential in changing tensile, thermal, and crystalline properties. The reduction in crystallinity was found correlated to the increasing amount of wool, though interlayer spacing of PCL was unaltered and overall thermal stability improved. The filaments were found printable through a 0.4 mm nozzle using a desktop 3D printer at 80 mm/min speed. The findings suggested the possible use of the produced filaments for fabrication of varied products, such as containers for holding or packing, toys, and other common household objects or industrial tools. [Display omitted] • Clean production of Waste wool/Polycaprolactone filaments for 3D printing. • Utilisation of the hydrophobicity of wool as an advantage with PCL matrix. • Tensile strength and biodegradation were improved by wool addition. • Finer fibre was influential in tensile, thermal, and crystalline properties. [ABSTRACT FROM AUTHOR]

Across the world, waste wool generated in farms and textile industries is often discarded without any utilisation. Low thermal stability of wool, i.e., melting of α-helix near 160 °C and degradation around 185–210 °C, further limits its use where a higher temperature is required. In the past, wool powder with slightly enhanced thermo-stability has been prepared using ionic liquids (from those containing toxic imidazole and pyridine), though the search for finding a sustainable and economic alternative is still ongoing. The current study proposes a conversion method of wool waste into highly thermo-stable micro-sized silica-modified powder through controlled disintegration of wool using a single-step chemical treatment. This study for the first time, reports an optimised method of wool powder preparation using sodium silicate solution while also maintains comparatively lower chemical to wool ratio among the previous reports. The properties of chemically prepared powder were thoroughly compared with powder of similar size prepared using mechanical milling. The chemical modification of wool showed improvement in its crystalline structure through α-helix to β-sheet transition and reduction in the interlayer spacing. The known high thermal stability of silicate groups significantly enhanced the thermal stability of the modified wool, given only 12–38% weight loss was recorded even at 600 °C. Overall, this research reveals an innovative method of transforming waste wool into thermally stable micro-sized powder for potential wider applications, such as high temperature extrusion, 3D printing, thermo-resistive coating, insulation in automotive and construction industries. [Display omitted] • Silica-modified wool powder was prepared by one-step chemical treatment. • Micro-sized particle was achieved using low chemical to wool ratio. • α-helix to β-sheet transition observed with improved crystallinity. • Thermal stability significantly increased by silicate integration. [ABSTRACT FROM AUTHOR]