Characterisation of watersoluble polysaccharides produced during prehydrolysis of pinus radiata

An aqueous prehydrolysate (or prehydrolysis liquor) was produced during a mild hot-water prehydrolysis (90 minute ramp to 175 C) of commercial radiata pine wood chips. Oligosaccharide and polysaccharide material was separated from the concentrated prehydrolysate using solvent precipitation after most of the noncarbohydrate material was removed. These polymeric carbohydrates were fractionated based on charge and molecular weight by size-exclusion chromatography (SEC). The fractions were each analysed by a number of methods including MALDI-ToF mass spectrometry, and NMR. A number of different types of carbohydrate polymer structures were found that were produced due to the partial de-polymerisation of the wood hemicelluloses during the prehydrolysis process. The O-acetylated (galacto)glucomannans were the most extensively characterised. These partially-acetylated hexose-based polymers were the main type found and accounted for approximately 54% by mass of the polymeric carbohydrates. Most appeared to contained between 5 and 79 hexose units with differing degrees of acetylation. The average mol ratio of components in these polymers was calculated to be approximately 3.7 : 1.3 : 1 : 0.2 (D-mannosyl : acetyl : D-glucosyl : D-galactosyl). They had a structure consistent with a linear backbone of β-1,4- linked D-mannopyranosyl and β-1,4-linked D-glucopyranosyl units with acetyl groups attached at C-2 and C-3 positions of some D-mannopyranosyl units. The terminal D-galactopyranosyl units were likely to be attached at 1,4,6-linked Dmannopyranosyl branch points. Of the neutral (non-anionic) polysaccharides, this type was most prevalent in the higher molecular weight fractions. Anionic pentose-based polymers with a backbone of β-1,4-linked D-xylopyranosyl units were also characterised. Identified as (arabino)glucuronoxylans, they featured uronic acid groups consistent with 4-O-methyl-α-D-glucopyranosyluronic acids attached to the C-2 position of some D-xylopyranosyl units. Smaller amounts of terminal α-L-arabinofuranosyl units likely to be attached at β-1,3,4- linked D-xylopyranosyl branch points were also detected. These polymers appeared to mostly contain between 5 and 40 pentose units with between 1 and 4 uronic acid groups attached. The anionic fractions (approximately 30% by mass) also contained large amounts of D-galactopyranosyl and L-arabinosyl units along with some D-glucuronic and D-galacturonic acid residues. This suggested the presence of carbohydrates produced from the partial hydrolysis of arabinogalactans and pectins. The smaller molecular weight fractions of non-anionic polysaccharides were enriched in both 1,4-linked D-galactopyranosyl units and non-acetylated hexosebased polymers that contained between 5 and 30 hexose units; this suggested that significant amounts 1,4-galactan derived carbohydrates were present. Small amounts of oligomers containing only pentose units were detected in these smaller molecular weight fractions along with what appeared to be other uncharged fragments of the polysaccharide-types that were present in the anionic fractions

Carbonisation of biomass-derived chars and the thermal reduction of a graphene oxide sample studied using Raman spectroscopy

Chars and carbonised chars were produced from three different oxygen-rich precursors (Pinus radiata wood, Phormium tenax leaf fibres, and sucrose crystals). These non-graphitisable carbons were analysed with Raman spectroscopy in order to study the nanostructural development which occurs with increasingly severe heat treatments up to approximately 1000 °C. The thermal reduction of a graphene oxide sample was similarly studied, as this is considered to involve the development of nanometre-scale graphene-like domains within a different oxygen-rich precursor. Increasing the heat treatment temperatures used in the charring and carbonisation processes, led to significant changes in a number of parameters measured in the Raman spectra. Correlations based on these parameter changes could have future applications in evaluating various char samples and estimating the heat treatment temperatures employed during their manufacture. After production heat treatment temperatures exceeded 700 °C, the Raman spectra of the carbonised chars appeared to be largely precursor independent. The spectra of these carbonised chars were similar to the spectra obtained from thermally-reduced graphene oxides, especially when compared to a wide range of other carbonaceous materials analysed using this particular methodology. Partial reduction of a graphene oxide sample due to reasonably mild laser exposures during Raman analysis was also observed

Studying carbonisation with raman spectroscopy

Raman spectroscopy can provide fast and non-destructive analysis of carbonaceous materials. As it is able to detect nanometre-sized structural features, Raman spectroscopy is widely used in the study of carbon nanotubes, fullerenes, graphenes, and many other carbon-rich materials. Raman analysis has previously shown potential for estimating the heat treatment temperatures (HTT) employed in the preparation of Japanese cedar charcoals which suggested future usefulness in quality control . In the current work, Raman spectroscopy was used to investigate the nanostructural development which had occurred within various chars prepared and carbonised at a range of heat treatment temperatures between ≈ 340°C and 1000°C. Chars were produced from sucrose sugar as standard precursor of high purity and two sources of biomass common in New Zealand (Radiata pine wood and Harakeke leaf fibres). In chars produced at lower HTTs, signals could be detected which were interpreted as representing hydrogen-rich amorphous carbon structures. In contrast, the Raman spectra of well-carbonised chars produced at higher HTTs featured signals consistent with graphene-like structures with coherent domains limited in size to below a few nanometres across. Measurement of such signals provides the ability to evaluate the extent of nanostructural development, identify char samples which are ‘undercooked’ when compared to other char samples, and estimate effective HTTs used in the production of a given char sample. More detailed Raman analysis of Radiata-derived chars was carried out, including analysis of chars produced from carbonising pyrolysis tars. Results of Raman analysis were correlated to H/C atom ratios obtained through elemental analysis for these chars produced from Radiata pine

Improving the alignment of dynamic sheet-formed mats by changing nozzle geometry and their reinforcement of polypropylene matrix composites

The main objective of this study was to improve the orientation of fibres within the mats produced using dynamic sheet forming (DSF). DSF is used to make fibre mats by forcing a fibre suspension through a nozzle onto a rotating drum. In this research, the effect of nozzle geometry on the orientation of hemp fibres within DSF mats was investigated. The orientation of fibres within the mats produced was assessed using ImageJ (OrientationJ) and X-ray diffraction. It was found that, as the contraction ratio of the nozzle increased, the orientation of fibres within the fibre mats increased. It was also found that the composite tensile strength increased with increased fibre orientation

Production and assessment of Poly(Lactic Acid) matrix composites reinforced with regenerated cellulose fibres for fused deposition modelling

Additive manufacturing can be a valuable tool to process polymeric composites reinforced with bio-based fibres, extending their use and opening new opportunities for more environmentally friendly materials. In this work, poly(lactic acid) (PLA) composites reinforced with regenerated cellulose fibres (lyocell) were processed into novel filaments and used for 3D printing. The Young's modulus of the filaments increased with the addition of fibres, but substantial porosity was observed in formulations with 20 and 30 wt% of fibre content. Nonetheless, the composites were easily printed, and the formulation with 10 wt% of fibres presented the best tensile properties of 3D printed samples with average tensile strength, Young's modulus, and strain at break of 64.2 MPa, 4.56 GPa, and 4.93%, respectively. It has been shown in this study that the printing process contributes to fibre alignment with small variations depending on the printing speed. Printed composite samples also had superior thermo-mechanical stability with a storage modulus up to 72 times higher than for neat PLA at 80 °C after the composite samples were heat-treated. In general, this work supports the potential use of regenerated cellulose fibres to reinforce PLA for 3D printing applications

Reviewing, Combining, and Updating the Models for the Nanostructure of Non-Graphitizing Carbons Produced from Oxygen-Containing Precursors

Following a review of the literature evidence, an updated model is presented to describe the kind of nanometer-scale structures that occur in non-graphitizing carbons (also known as chars, biocarbons, and biochars) produced from the carbonization of oxygen-containing precursors (especially carbohydrates and lignocellulosic biomass). This is not intended to be a new model, because it is still essentially the same general model and concepts put forward by Franklin in 1951 and updated through integrating additional experimental evidence, ideas, and key features published over the last 64 years. The updated model uses evidence and concepts from recent publications on graphene oxide and reduced graphene oxide to assist in explaining a potential role of heteroatoms (especially oxygen) in the cross-linking, which is considered important in the development of the distinct nanostructure of non-graphitizing carbons. A three-dimensional molecular/atomic model is presented to approximate the nanostructure formed as carbonization temperatures approach 1000 °C. The development of this nanostructure over a range of carbonization temperatures is also described