Recent advances in sago (Metroxylon sagu) fibres, biopolymers, biocomposites, and their prospective applications in industry: A comprehensive review

Escalating petroleum depletion and environmental crises linked to conventional plastics have fueled interest in eco-friendly alternatives. Natural fibres and biopolymers are garnering increasing attention due to their sustainability. The sago palm (Metroxylon sagu), a tropical tree, holds potential for such materials, with cellulose-rich fibres (42.4-44.12 %) showcasing strong mechanics. Extracted sago palm starch can be blended, reinforced, or plasticised for improved traits. However, a comprehensive review of sago palm fibres, starch, and biocomposites is notably absent. This paper fills this void, meticulously assessing recent advancements in sago palm fibre, cellulose and starch properties, and their eco-friendly composite fabrication. Moreover, it uncovers the latent prospects of sago palm fibres and biopolymers across industries like automotive, packaging, and bioenergy. This review presents a crucial resource for envisaging and realising sustainable materials.

Effect of the age of garments used under real-life conditions on microfibre release from polyester and cotton clothing

The release of microfibres from fabrics during laundering represents an important source of plastic and natural microfibres to aquatic environments. Garment age - how long the garment has been used - could be a key factor influencing the rate of release, yet most studies of microfibre shedding have only assessed newly manufactured products. To this end, we quantified microfibre release during laundering in domestic washing machines from polyester (PES) and cotton garments (n = 38) used in real-life conditions for periods between 1 and 31 years with different use intensities. In addition, to better understand the factors involved in microfibre releases, fibre composition (different PES percentages) and type of garments (T-shirts, polo shirts, uniforms, sports shirts, and sweatshirts) were examined. All garments released microfibres during washing, while the older garments presented higher releases for clothing with a PES/cotton blend. In general, older garments (15-31 years) released nearly twice as many fibres when washed than newer garments (1-10 years). The mass of microfibres released was consistently greater in garments with a higher proportion of cotton than PES (up to 1.774 mg g-1 in 2% PES and 0.366 mg g-1 in 100% PES fabrics), suggesting that cotton might be released more readily such that the relative proportion of PES in the garments could increase over time. Additionally, SEM images showed fibre damage, with fibres from the older garments exhibiting more peeling and splitting. While it is important to note that the overall environmental footprint is undoubtedly reduced by keeping garments in use for longer periods of time, older garments were shown to release more microfibres.

Investigation of TiO2 Nanoparticles Influence on Tensile Properties and Thermal Stability of Dry and Wet Luffa-Epoxy Nanocomposites

BACKGROUND

Recently, progress has been made toward understanding the efficiency of polymer composites with natural fibres. With the hope of enhancing the characteristics of polymer composites supplemented with natural fibres in a watery environment, TiO2 nanoparticles have been used to improve their performance in the field.

METHOD

These nanoparticles were filled in luffa-epoxy components at 1, 3, and 5 % volume fractions. A combination of x-ray diffraction and Fourier transform infrared spectroscopy was utilized to conduct the structural examinations. The nanoparticle spread was captured by field emission scanning electron microscopy.

RESULT

Results show that dry nanocomposite's tensile strength and modulus have increased by 74% and, 13%, 137%, and 50% compared with epoxy and 40 vol% luffa-epoxy [E/L] composites, respectively. In wet nanocomposites, maximum reduction in tensile strength and modulus were observed as 27.4% and 16.54%, respectively. The diminished water absorption and thickness swelling percentage of nanocomposites were recorded as 98% and 91.8%, respectively. The onset temperature of these nanocomposites was scattered in the range of 379-393°C, with a maximum char residue of 38%.

CONCLUSION

The increase in the percentage of residue indicates the effectiveness of epoxy's flame retardant, improved thermal stability, diminished water absorption [approximately 2%], and 95% retention of wet composites' tensile properties. These results provided data support for improving the application of nanocomposites in the automobile field.

Chemical, thermal and morphological properties of polybutylene succinate-waste pineapple leaf fibres composites

The use of natural fibres for polymer composite applications has been widely researched due to the biodegradable and lightweight nature of natural fibres. To achieve good adhesion and compatibility between the matrix and the fibre filler, prior modification of the fibre surface via the use of various methods has been found to be effective. The natural fibres have been modified using chemical, physical, radiation, grafting and biological methods. The current study aims to evaluate the effect of sodium hydroxide-treated waste pineapple leaf fibres (PALF) content on the chemical, thermal, and morphological properties of polybutylene succinate (PBS) composites. PBS-PALF composites with fibre content ranging from 0 to 20 wt% were prepared using an internal mixer and their properties were studied using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA) and Scanning electron microscope (SEM). The FTIR results showed no noticeable functionality differences among the composites, however, carbonyl groups from PBS polymer at ∼1700 cm-1 and hydroxyl groups from PALF at ∼3000 cm-1 were observed in the composites. The water absorption uptake of the composites increased with fibre content due to the hydrophilic nature of the PALF fibres and the highest water absorption percentage achieved was ∼30 %. The incorporation of the fibres into the PBS matrix decreased the crystallinity of the composites as shown by the XRD peaks at 2ϴ = 22 and 30°. SEM images of the composites with 20 wt% exhibited morphologies where the fibres protruded out from the polymer matrix, and this was ascribed to the agglomerated fibres which were poorly mixed with the matrix at the higher fibre content. Overall, the incorporation of high PALF content in the composites disrupted the crystallinity and thermal stability of the PBS matrix. The composites have potential in industrial agricultural mulching film applications due to their sustainability characteristics.

A mini-review on building insulation materials from perspective of plastic pollution: Current issues and natural fibres as a possible solution

As plastic pollution is eroding our ecological environment at an alarming rate around the world, tracking the origins is a necessity for putting forward effective measures to prevent it. The building industry, as an important sector consuming plastic products and producing plastic wastes, is increasing application of thermal insulations to improve energy efficiency. However, most insulation materials have negative impact on the environment. With the strategies to boost sustainability of buildings, natural fibres have occurred in the market as promising raw materials for thermal insulations. This mini-review aims to describe the extent building insulations contributed to plastic pollution, and a possible solution to plastic pollution from natural fibres and their current shortcomings. Hopefully, the mini-review could advance the current knowledge on contribution of building materials, especially thermal insulations to the ubiquitous plastic pollution, and the potential of natural fibres for replacing the plastic insulations, which could accordingly help future development of sustainable green insulations.

Textile ageing due to atmospheric gases and particles in indoor cultural heritage

Textile fibre degradation can be due to many factors. The most common cause is light exposure, but upon the lifespan of a textile, many other environmental factors are to be taken into account. This study focuses on the role of atmospheric compounds-both particulate and gaseous species-on natural textiles ageing, more specifically cotton, silk and wool. To achieve this, reference samples of textiles were exposed to contrasted environments (marine, urban and semi-rural museums and historical buildings) for natural ageing. These conditions were also reproduced in an experimental chamber dedicated to the study of the impact of airborne pollutants on heritage materials. Experimental ageing allowed to highlight degradation mechanisms for each fibre: SO₂ and HCOOH cause the cleavage of cotton's glyosidic links and silk's peptide bonds, while NO₂ promotes the oxidation of the fibres. The most harmful pollutant towards cotton is NO₂ since it causes both its oxidation and hydrolysis. The case of wool is more complicated: HCOOH provokes peptide link cleavage (similarly to silk) but this fibre is less sensitive to SO₂ attacks than silk and even seems to be protected against future alterations after having been firstly exposed to this pollutant. In any case, this experimental study evidences that damages caused by gaseous pollutants are fostered by the presence of particles, regardless of the chemical composition of the particle coating.

Zinc oxide nanostructures and stearic acid as surface modifiers for flax fabrics in polylactic acid biocomposites

Different surface treatments including mercerization, stearic acid and growth of zinc oxide nanorods as well as their combinations were exploited to address their effects on the properties of green composites based on polylactic acid (PLA) and flax fabrics. The resulting fabrics were morphologically (SEM), crystallographically (XRD) and thermally (TGA) characterized, showing no significant changes with respect to the untreated samples. In contrast, tensile and flexural properties of composites produced by compression moulding were significantly influenced. A combination of mercerization and environmentally friendly stearic acid treatment turned the character of the flax fabric from hydrophilic to hydrophobic, and led to improved bending and tensile strengths by 20% and 12%, respectively, compared to untreated composites. The presence of ZnO nanorods promoted an increase in flexural and tensile stiffness by 58% and 31%, respectively, but at the expense of strength, with reductions ascribed to the degradation of polylactic acid under high-temperature conditions favoured by ZnO, as confirmed by a reduction in the initial thermal degradation temperature up to 26%. These latter composites can be suggested in those applications where a suitable combination of flexural properties and a shorter persistence in the environment is desired.

Analysis of the foam-forming of non-woven lightweight fibrous materials using X-ray tomography

Abstract

Foam-forming has in the past predominantly been used to create two-dimensional sheet-like fibrous materials. Allowing the foam to drain freely and decay under gravity, rather than applying a vacuum to remove it rapidly, we can produce lightweight three-dimensional fibrous structures from cellulose fibres, of potential use for thermal and acoustic insulation. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu$$\end{document}μCT scanning of the fibrous materials enable us to determine both void size distributions and also distributions of fibre orientations. Through image analysis and uniaxial compression testing, we find that the orientation of the fibres, rather than the size of the voids, determine the compressive strength of the material. The fibrous samples display a layering of the fibres perpendicular to the direction of drainage of the precursor liquid foam. This leads to an anisotropy of the compressive behaviour of the samples. Varying the initial liquid fraction of the foam allows for tuning of the compressive strength. We show an increase in over seven times can be achieved for samples of the same density (13 kg.m^-3).

Graphic abstract

Potential use of coconut fibre modified mortars to enhance thermal comfort in low-income housing

Enhancing the thermal comfort of low-income housing in developing countries located in tropical areas is one of the main challenges for engineers and architects worldwide. The coconut mesocarp fibre (coir) has shown enormous potential for improving some properties of modified concretes or mortars, such as low-weight and high-acoustic isolation. In this study, the potential use of modified mortars by coconut fibres as a facade coating layer to enhance thermal comfort in low-income housing structures was evaluated for the city of Cartagena de Indias, Colombia. An actual typical low-income house of 42 m² was monitored. Temperature and humidity variations were monitored for 39 days, thermal characteristics of coir-modified mortars were also investigated using differential scanning calorimetry (DSC) and an adaptation of the standard test method of the guarded-hot-cartridge apparatus. The EnergyPlus™ software was used to simulate indoor temperature variations in the studied house. Results show that during the period of 4 h of maximum sunlight radiation with outdoor temperatures in the range of 29-34 °C, coating the cement-sand hollow block structure with a layer of coir-modified mortar could reduce indoor room temperatures by 0.5-1.5 °C, approximately. Thus, there is a potential to enhance the thermal comfort in low-income housing structures with coconut fibre modified mortars while reducing annual energy costs of cooling by 16%, making it affordable for low-income families in the Caribbean region of Colombia.

From aviation to automotive - a study on material selection and its implication on cost and weight efficient structural composite and sandwich designs

The design of a composite material structure is often challenging as it is driven by the trade-off between lightweight performance and production costs. In this paper, the boundaries of this design trade-off and its implications on material selection, geometrical design and manufacturability are analysed for a number of design strategies and composite material systems. The analysis is founded on a methodology that couples weight-optimization and technical cost modelling through an application-bound design cost. Each design strategy is evaluated for three levels of bending and torsional stiffness. The resulting stiffness-versus cost-range together constructs the design envelope and provides guidelines on the suitability and improvement potential of each case. Design strategies researched include monolithic, u-beam-, sandwich-insert- and sandwich-stiffened plates. Considered material systems include carbon-, glass, recycled carbon-, lignin- and hemp-fibre reinforced composites. Optimized sandwich designs are shown to have lowest design cost. Glass-, recycled carbon-, lignin- and hemp-fibre reinforced composite materials are all shown to reduce costs but at lower stiffness performance. Ultimately, the case study demonstrates the importance of early structural design trade-off studies and material selection and justifies introducing novel fibre systems in low-cost applications of moderate stiffness levels.

Inverse gas chromatography for natural fibre characterisation: Identification of the critical parameters to determine the Brunauer-Emmett-Teller specific surface area

Inverse gas chromatography (IGC) is an alternative technique to determine the specific surface area of natural fibres. Natural fibres have a complex surface chemistry and unique microstructure that challenge the current capabilities to perform surface characterisation. This study investigated the influence of multiple parameters on the measured Brunauer-Emmett-Teller (BET) specific surface area for samples of flax, kenaf and BioMid(®) cellulose fibres using IGC. The BET surface area of kenaf and flax differed with 0.51m(2)g(-1) and 1.35m(2)g(-1) respectively, the former being similar to the cellulose fibres (0.54m(2)g(-1)). The data was calculated under conditions where the BET equation showed good linearity (R(2)⩾0.995). Repeatability was excellent so that two runs sufficed to obtain representative BET surface area values. The findings showed the choice of solvent was important for all specimens to avoid any misleading data comparison due to molecular orientation effects that impact the adsorbent-adsorbate interactions. The higher surface area of the flax sample, and its higher variability, was correlated with a higher surface roughness observed under optical microscopy. Packing the chromatography column with long or chopped fibres produced results that were statistically insignificant.

Qualitative and quantitative assessment of water sorption in natural fibres using ATR-FTIR spectroscopy

In the field of composite materials, natural fibres appear to be a viable replacement for glass fibres. However, in humid conditions, strong hydrophilic behaviour of such materials can lead to their structural modification. Then, understanding moisture sorption mechanisms in these materials is an important issue for their efficient use. In this work, the water sorption on three natural fibres (flax, hemp and sisal) was studied using Fourier transformed infrared spectroscopy. The spectral information allowed both qualitative and quantitative analyses of the moisture absorption mechanisms. The main chemical functions involved in the water sorption phenomenon were identified. The absolute water content of the fibres was also determined by using a partial least square regression (PLS-R) approach. Moreover, typical sorption isotherm curves described by Park model were fitted as well as water diffusion kinetics. These last applications confirmed the validity of the FTIR spectra based predictive models.