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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. [ABSTRACT FROM AUTHOR]

Fused deposition modelling (FDM) is considered the most popular technique of three-dimensional (3D) printing. This is a simple and sustainable method of materials manufacturing with rapidly spreading applications in diverse areas. In this method, a thermoplastic filament is extruded through a nozzle on a layer-by-layer basis to construct a 3D object in a benchtop environment. To further promote its acceptance, FDM printing currently has a significant focus on the use of natural fillers with thermoplastic polymer. Nevertheless, successful FDM printing is largely dependent on the strength and consistency of the feed material, the filament. Preparing such composite filaments is challenging due to possible manufacturing defects and inconsistency while mixing the filler and matrix. Studies showed that there are significant differences between the tensile properties of FDM filament when compared with their printed parts, caused by the variations in printing parameters, filament consumption, density, and architectural difference. Previous reports have confirmed that mechanical characteristics are the most common parameters used by scientists to evaluate the properties of the materials in the additive manufacturing field. Though several reviews are accessible on the tensile properties of FDM-printed materials, currently there is no review available on the tensile properties of the filament itself. This is the first review focused exclusively on the tensile properties of FDM filaments. The goal of this short review is to better understand the influential factors in the natural fibre-reinforced filament preparation process that affect the tensile properties and subsequently impact on 3D printing. Therefore, evaluation of the reported tensile properties, i.e., tensile strength and elongation at the break and modulus, was conducted in relation to different process parameters, such as filler concentration, filler size, extrusion methods, the combination of filler and polymer, and the interrelations among the parameters and properties were explored. [ABSTRACT FROM AUTHOR]

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]

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. [ABSTRACT FROM AUTHOR]

Natural wastes are widely used as composts for plant growth. However, wool waste has received little attention in this regard, despite its nitrogen-rich chemical structure owing to amide groups. A few studies have been conducted for soil amendment using wool, mostly in raw or pellet form. However, despite the possible consistent mixing and more uniform effect of powders inside soil, wool has never been implemented in powder form in soil for improving moisture. This study demonstrates the effectiveness of using wool as a powder, facilitating better mixing and spreading in soil. Results show that wool powders are more effective in retaining soil moisture compared to wool pellets and are comparable to commercial fertiliser. The findings further indicate that a balanced amount of wool is required to maintain a proper moisture level (not too wet or dry) to promote actual plant growth. [ABSTRACT FROM AUTHOR]

The extensive use of dyes in numerous industries results in massive dye discharge in the wastewater, which is a major cause of water pollution. Globally, the consumption of dyes is near seven hundred thousand tons across different sectors, of which around 10–15% goes into the wastewater. Among the dye kinds, anionic dyes make up the main proportion, having a 32–90% share in the wastewater. Different plant-derived wastes, which are sustainable given their natural abundance, effectiveness, and low cost, are frequently proposed for dye separation. However, these adsorbents are inherently more suitable for cationic dyes than anionic dyes. In recent years, the modification of these wastes has been progressively considered to suit them to anionic dye removal. These modifications involve mechanical, thermal, or chemical treatments, or combinations. These attempts propose two-way benefits, as one abundant waste is being used to cure another severe problem, and eventually both could be diminished. This review has a key focus on the evaluation of plant-derived adsorbents and their modifications, and particularly for anionic dye adsorption. Overall, the mechanism of adsorption and the suitability of the current methods are discussed, and their future potential is explored. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Three types of vinyl sulphone dyes were measured in the effluent in this study. The selected dyes were Remazol Yellow RR (mono-functional), Remazol Blue RR (homo bi-functional) and Remazol Red RR (hetero bi-functional). The extinction coefficients of these dyes were measured by creating absorbance versus concentration curves. The absorbance values were obtained by testing standard solutions of each dye in a UV–visible spectrophotometer. The dyeing process was carried out at 4 different dye concentrations (0.025 g/40 ml, 0.05 g/40 ml, 0.10 g/40 ml and 0.15 g/40 ml) on a 5-g fabric sample for each of the dyes. The post-dye liquors and post-wash liquors were tested in an UV–visible spectrophotometer, and their concentrations were calculated using the Beer–Lambert law. The contribution of these dyes to the effluent was calculated and compared, and their adsorption isotherms (Langmuir and Freundlich isotherm) were analysed. The homo bi-functional dye (Blue RR) performed well in the dye bath, but it contributed significantly to the effluent during the washing stages. The mono-functional dye (Yellow RR) was able to adsorb, but it did not perform well due to its greater heterogeneity. The hetero bi-functional Red RR dye was found to be the most environmentally friendly in comparison with the other vinyl sulphone dyes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new cost-effective approach for producing bio-plastic from the combination of poly (vinyl alcohol) (PVA) and cotton gin trash (CGT) is reported in this study intended for probable replacement of non-biodegradable plastics in packaging. The effect of diethylene glycol, glycerol and urea as plasticisers and ethyl cellulose (EC) as coating agent were investigated. The plasticising effect was governed by the synergistic influence of the solubility parameter, molecular weight and the linearity of the plasticisers' chemical structure. A better plasticising effect reduced the vacant areas at CGT/PVA interfaces, and decreased the crystallinity and tensile strength, while improved the moisture absorption, transmission and thermal stability. Urea, as the plasticiser, showed the best performance among others (modulus 257 MPa, slightly higher than that of commercial LDPE (213.5 MPa), followed by glycerol. With complete flexibility (folding endurance >200), the tensile strength of the composite films was higher than LDPE. The film coated with EC was able to resist water drop penetration at least for 10 min. The films were semi-transparent and have excellent UV resistance. The related cost of electricity and chemicals per gram film production was estimated around 0.02 and 0.18–0.19 AUD, respectively. Overall, this study showed a sensible method of producing water-resistant flexible bio-plastic that could be beneficial in encountering current plastic pollution. [Display omitted] • Flexible cotton gin trash (CGT)/poly(vinyl alcohol) (PVA) plastic was developed. • New method to induce water-resistant property to CGT/PVA plastic was proposed. • CGT/PVA plastics showed relatively similar modulus and higher tensile strength to LDPE. • Thermal stability of PVA enhanced by CGT and complete UV protection achieved. [ABSTRACT FROM AUTHOR]