Assessing Cellulose Micro/Nanofibre Morphology Using a High Throughput Fibre Analysis Device to Predict Nanopaper Performance

Characterising cellulose nanofibre (CNF) morphology has been identified as a grand challenge for the nanocellulose research field. Direct techniques for CNF morphology characterisation exhibit various difficulties related to the material network structure and equipment cost, while indirect techniques that investigate fibre-light interaction, fibre-solvent interaction, fibre-fibre interaction, or specific fibre surface area involve relatively facile methods but may be more unreliable. Nanopaper mechanical testing is a prevalent metric for assessing fibre-fibre interaction, but is an off-line, time-consuming, and destructive methodology. In this study, an optical fibre morphology analyser (MorFi, TechPap) was employed as an on-line, high throughput, fast turnaround tool to assess micro/nanofibre pulp morphology and predict the properties of nanopaper material. Correlation analysis identified fibre content and fibre kink properties as most correlated with nanopaper strength and toughness, while fibre width and coarseness were most inversely correlated with nanopaper performance. Principal component analysis (PCA) was employed to visualise interdependent morphological and mechanical data. Subsequently, two data driven statistical models - multiple linear regression (MLR) and machine learning based support vector regression (SVR) - were established to predict nanopaper properties from fibre morphology data, with SVR generating a more accurate prediction across all nanopaper properties (NRMSE = 0.13-0.33) compared to the MLR model (NRMSE = 0.33-0.51). This study highlights that statistical methods are useful to disentangle and visualise interdependent morphological data from an on-line fibre analysis device, while regression models are also capable of predicting paper mechanical properties from CNF samples even though these devices do not operate at nanoscale resolution.

SOLVENT OPTIMIZATION OF ELECTROSPUN POLY(ACRYLIC ACID) NANOFIBERS

In this study, it was investigated experimentally the influence of various solvents (distilled water and ethanol) on the solution properties, spinning performance, and fibre morphology of the electro spun Poly (acrylic acid) nanofibers. Firstly, polymer solutions were prepared at 5 wt % PAA with various solvent ratios of ethanol and distilled water. Then, solution properties such as viscosity, density, pH, conductivity, and surface tension were determined. The production of nanofiber samples was carried out by electrospinning under the optimum process parameters (voltage, distance between electrodes, feed rate, and atmospheric conditions). Finally, the morphological characterization of the nanofiber surface was carried out with SEM. According to the results, it was observed that conductivity, surface tension and the density of the solution increase as the ethanol ratio decreases. On the other hand, pH value increases as the ethanol ratio increases and, so, the acidic value of the solutions decreases. The viscosity increased until the ethanol/distilled water ratio was 50/50 and then decreased as the ethanol percentage decreased to under 50%. In addition, average fibre diameter decreases with ethanol ratio decreases. It is possible to say that solvent type affects solution properties, fibre morphology and spinning performance significantly. Generally, fine, uniform and bead free nanofibers could be electro spun and the PAA solution containing 70 wt % distilled water and 30 wt % ethanol was selected as the optimum in terms of fibre morphology, web quality and spinning performance.

Anatomical characterization of Chimonobambusa quadrangularis based on circumferential and radial variation patterns in cross-sections

The anatomical structure of the bamboo stem is characterized by vascular bundles comprising the xylem, phloem, and sclerenchyma fibrous sheaths as well as parenchymatous ground tissue in which the vascular bundles are embedded. The composition of the stem is the main factor influencing the anatomical characteristics of circular bamboo, which shows considerable variation in the radial direction. However, most species of Chimonobambusa have square stems. Here, we tested the hypothesis that circumferential variation exists in the cross-sectional anatomy of this species. We analysed fibre morphology and the cross-sectional structural characteristics of vascular bundles of Chimonobambusa quadrangularis (Fenzi) Makino and their associated circumferential and radial variation in cross-sections. Microscopic observations were conducted to identify, measure, and compare fibre morphology and the structural characteristics of vascular bundles, including both circumferential and radial anatomical variation. Vascular bundles occurred as undifferentiated, semi-differentiated, and open types in the radial direction with no changes in the circumferential direction. The average length, width, and ratio of fibre length to width were 1463.6 μm, 12.3 μm and 119.3 in the corner region, and 1452.7 μm, 12.8 μm, and 111.3 in the side region, and there were significant circumferential and radial differences in length, width, and the ratio of fibre length to width (). The circumferential variation in density of vascular bundles, the ratio of fibre length to width, radial to tangential diameter ratio of vascular bundles, and the proportion of sclerenchyma were greater in the corner regions than the side regions. The variation in fibre width and the proportion of parenchyma were greater in the corner regions than in the side regions. The density of vascular bundles and proportions of sclerenchyma were greater in the outer stem compared to the inner stem, whereas the length, width, and ratio of fibre length to width were greatest in the centre compared to the inner and outer zones. Circumferential variation of the density of vascular bundles, fibre length and fibre width occurred in the central and outer stem zones. These findings confirm that there are significant anatomical variations in both the circumferential and radial directions and provide a scientific basis for the rational use of Chimonobambusa quadrangularis.

Hierarchically Assembled Type I Collagen Fibres as Biomimetic Building Blocks of Biomedical Membranes

Wet spinning is an established fibre manufacturing route to realise collagen fibres with preserved triple helix architecture and cell acceptability for applications in biomedical membranes. However, resulting fibres still need to be chemically modified post-spinning to ensure material integrity in physiological media, with inherent risks of alteration of fibre morphology and with limited opportunities to induce fibrillogenesis following collagen fixation in the crosslinked state. To overcome this challenge, we hypothesised that a photoactive type I collagen precursor bearing either single or multiple monomers could be employed to accomplish hierarchically assembled fibres with improved processability, macroscopic properties and nanoscale organisation via sequential wet spinning and UV-curing. In-house-extracted type I rat tail collagen functionalised with both 4-vinylbenzyl chloride (4VBC) and methacrylate residues generated a full hydrogel network following solubilisation in a photoactive aqueous solution and UV exposure, whereby ~85 wt.% of material was retained following 75-day hydrolytic incubation. Wide-angle x-ray diffraction confirmed the presence of typical collagen patterns, whilst an averaged compression modulus and swelling ratio of more than 290 kPa and 1500 wt.% was recorded in the UV-cured hydrogel networks. Photoactive type I collagen precursors were subsequently wet spun into fibres, displaying the typical dichroic features of collagen and regular fibre morphology. Varying tensile modulus (E = 5 ± 1 − 11 ± 4 MPa) and swelling ratio (SR = 1880 ± 200 − 3350 ± 500 wt.%) were measured following post-spinning UV curing and equilibration with phosphate‑buffered saline (PBS). Most importantly, 72-h incubation of the wet spun fibres in PBS successfully induced renaturation of collagen-like fibrils, which were fixed following UV-induced network formation. The whole process proved to be well tolerated by cells, as indicated by a spread-like cell morphology following a 48-h culture of L929 mouse fibroblasts on the extracts of UV-cured fibres.

Study of Air Pressure and Velocity for Solution Blow Spinning of Polyvinylidene Fluoride Nanofibres

Solution blow spinning (SBS) is gaining popularity for producing fibres for smart textiles and energy harvesting due to its operational simplicity and high throughput. The whole SBS process is significantly dependent on the characteristics of the attenuation force, i.e., compressed air. Although variation in the fibre morphology with varying air input pressure has been widely investigated, there is no available literature on the experimentally determined flow characteristics. Here, we have experimentally measured and calculated airflow parameters, namely, output air pressure and velocity in the nozzle wake at 12 different pressure values between 1 and 6 bar and 11 different positions (retracted 5 mm to 30 mm) along the centreline. The results obtained in this work will answer many critical questions about optimum protrusion length for the polymer solution syringe and approximate mean fibre diameter for polyvinylidene fluoride (PVDF) at given output air pressure and velocity. The highest output air pressure and velocity were achieved at a distance of 3–5 mm away from the nozzle wake and should be an ideal location for the apex of the polymer solution syringe. We achieved 250 nm PVDF fibres when output air pressure and velocity were 123 kPa and 387 m/s, respectively.

WOOD ANATOMICAL STUDIES REVEAL TAXONOMIC RELATIONSHIPS, ENVIRONMENTAL INFLUENCE AND PULP POTENTIAL IN FOUR TAXA OF Mussaenda (RUBIACEAE) GROWN IN NIGERIA

Current study was carried out to assess the taxonomic, ecological significance, and paper making potential of four taxa of Mussaenda L. (Rubiaceae) viz., M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ through wood anatomical studies. Each of the taxa was collected from its natural region of provenance in two different ecological zones (Derived Savanna and Tropical Rainforest) of Nigeria. Observations from different planes of sections were made and wood maceration was carried out for fibre morphology. Absent to scanty paratracheal axial parenchyma, septate fibres, pitted vessels, storied heterocellular rays, and simple perforation plates were common features in all taxa. However, multiseriate and wider rays distinguished the exotic species from the indigenous species, and the semi-diffuse porous wood pattern was a unique feature in M. ‘Dona Aurora’. Quantitative data showed considerable variations in case of fibre lengths among the four taxa i.e. M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ and was recorded 0.80 ± 0.02 µm, 0.70 ± 0.05 µm, 0.65 ± 0.03 µm and 0.64 ± 0.04 µm respectively. These observations showed that all species belong to Wood Type II of Rubiaceae and support their inclusion in the Tribe Mussaendeae and Order Ixoroideae. The influence of environmental factors was evident in the significant elongation of wood vessels of samples collected from more humid areas, but with no significant effect on their paper-making potential. More so, M. “Doña Aurora”, had general scores, would be most suitable for pulp and paper making.

WOOD ANATOMICAL STUDIES REVEAL TAXONOMIC RELATIONSHIPS, ENVIRONMENTAL INFLUENCE AND PULP POTENTIAL IN FOUR TAXA OF Mussaenda (RUBIACEAE) GROWN IN NIGERIA

Current study was carried out to assess the taxonomic, ecological significance, and paper making potential of four taxa of Mussaenda L. (Rubiaceae) viz., M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ through wood anatomical studies. Each of the taxa was collected from its natural region of provenance in two different ecological zones (Derived Savanna and Tropical Rainforest) of Nigeria. Observations from different planes of sections were made and wood maceration was carried out for fibre morphology. Absent to scanty paratracheal axial parenchyma, septate fibres, pitted vessels, storied heterocellular rays, and simple perforation plates were common features in all taxa. However, multiseriate and wider rays distinguished the exotic species from the indigenous species, and the semi-diffuse porous wood pattern was a unique feature in M. ‘Dona Aurora’. Quantitative data showed considerable variations in case of fibre lengths among the four taxa i.e. M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ and was recorded 0.80 ± 0.02 µm, 0.70 ± 0.05 µm, 0.65 ± 0.03 µm and 0.64 ± 0.04 µm respectively. These observations showed that all species belong to Wood Type II of Rubiaceae and support their inclusion in the Tribe Mussaendeae and Order Ixoroideae. The influence of environmental factors was evident in the significant elongation of wood vessels of samples collected from more humid areas, but with no significant effect on their paper-making potential. More so, M. “Doña Aurora”, had general scores, would be most suitable for pulp and paper making.

WOOD ANATOMICAL STUDIES REVEAL TAXONOMIC RELATIONSHIPS, ENVIRONMENTAL INFLUENCE AND PULP POTENTIAL IN FOUR TAXA OF Mussaenda (RUBIACEAE) GROWN IN NIGERIA

Current study was carried out to assess the taxonomic, ecological significance, and paper making potential of four taxa of Mussaenda L. (Rubiaceae) viz., M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ through wood anatomical studies. Each of the taxa was collected from its natural region of provenance in two different ecological zones (Derived Savanna and Tropical Rainforest) of Nigeria. Observations from different planes of sections were made and wood maceration was carried out for fibre morphology. Absent to scanty paratracheal axial parenchyma, septate fibres, pitted vessels, storied heterocellular rays, and simple perforation plates were common features in all taxa. However, multiseriate and wider rays distinguished the exotic species from the indigenous species, and the semi-diffuse porous wood pattern was a unique feature in M. ‘Dona Aurora’. Quantitative data showed considerable variations in case of fibre lengths among the four taxa i.e. M. elegans, M. erythrophylla, M. philippica var. aurorae, and M. ‘Dona Aurora’ and was recorded 0.80 ± 0.02 µm, 0.70 ± 0.05 µm, 0.65 ± 0.03 µm and 0.64 ± 0.04 µm respectively. These observations showed that all species belong to Wood Type II of Rubiaceae and support their inclusion in the Tribe Mussaendeae and Order Ixoroideae. The influence of environmental factors was evident in the significant elongation of wood vessels of samples collected from more humid areas, but with no significant effect on their paper-making potential. More so, M. “Doña Aurora”, had general scores, would be most suitable for pulp and paper making.

Effect of Sodium Hydroxide (NaOH) Treatment on Coconut Coir Fibre and its Effectiveness on Enhancing Sound Absorption Properties

Natural fibre has been conventionally and widely utilised as a sound absorber in order to replace the traditional synthetic absorber materials. In this study, coir fibre (CF) was prepared as an acoustic absorber and subjected to an additional surface treatment by using sodium hydroxide (NaOH) at various concentrations ranging from 1% to 8%. This was geared towards analysing the effect of alkalisation on the fibre morphology, diameter, and changes occurring in the CF functional groups, thus resulting in enhanced sound absorption properties. To this end, the fibre surface was analysed using a scanning electron microscopy (SEM) to study the surface morphology of treated and untreated CF materials, whereas the implementation of Fourier-transform infrared (FTIR) allowed an analysis of CF characterisation. The absorber sample was fabricated at a constant thickness of 45mm and a density of 0.4g/cm3 density prior to testing for the sound absorption coefficient (SAC) by using an impedance tube. The morphology of CF revealed the treated fibres to be free of impurities including lignin and hemicellulose layer, which were removed from their surface. This finding was supported by the peak changes observed on the FTIR spectra. Furthermore, the fibre diameter was reduced as the concentrations of NaOH increased. The results conclusively indicated that treated CF at the concentrations of 7% and 8% NaOH gained the highest SAC values across the low and high-frequency ranges, yielding an α coefficient average of 0.9 and above.