The pulping industry, dominated by century-old technologies, is highly polluting, making imperative finding more environmentally friendly alternatives. The ionoSolv process, based on the use of low-cost protic ionic liquids, is one of the most promising methods to fractionate lignocellulose with low ecological impact. However, this process has been only optimized to produce sugar-derived chemicals, where fibre quality is not a key factor. Earlier studies have shown the detrimental effect of the standard ionoSolv conditions on fibre length, which renders them unsuitable for fibre applications, including the production of paper. For the first time, this study shows the optimization of the ionoSolv fractionation of Miscanthus to preserve key fibre properties of the pulps, namely fibre dimensions, degree of polymerization and relative molecular mass, while maintaining optimal purity. Different temperatures (150 degrees C and 170 degrees C), retention times (45-90 min), and acid:base ratios (a:b = 1.00 to a:b = 0.55) were investigated. Fractionation at 170 degrees C for 45 min with a reduced acid:base ratio of a:b = 0.86 allowed for maximum delignification (lignin content of 4.4 %) and preservation of fibre length. Pulps recovered under optimal conditions were bleached using a single stage method based on H2O2 increasing pulp purity, achieving optimal decolorization and retaining fibre dimensions comparable to those obtained from a commercial process (Lc(l) = 0.509 mm and Lc(w) = 0.775 vs Lc(l) = 0.540 mm and Lc(w) = 0.975). This highlights the potential of the ionoSolv process as a greener fractionation alternative to produce cellulose fibre materials.

The effect of Micro-Fibrillated Cellulose (MFC) on the interfacial friction between ceramic and glass was investigated as a function of the applied load, surface roughness, sliding distance, sliding velocity, and liquid present. With a normal load of 4 N, high friction was observed whilst maintaining a low wear. Increasing the roughness (Ra) of the ceramic substrate from 0.99 to 3.01 µm could result in a slight increase in the Coefficient of Friction (CoF) from 0.36 to 0.46, but a remarkable increase in wear (depth of the wear track) from 0.27 to 1.31 µm. Friction and wear thresholds were identified after a sliding distance of 400 mm, whilst an increased sliding velocity could reduce both friction and wear. This study also investigated MFC with Xanthan Gum (XG), both with similar rheological behaviour, confirming that the physical presence of fibres in the formulation was responsible for the improved interfacial lubrication.

The use of microfibrillated cellulose (MFC) in the paper industry has become established following many years of development by both academic and industrial researchers. Commercial installations typically use mechanical disintegration techniques such as refiners and grinders to convert aqueous suspensions of pulp fibres into a material consisting of fibrils and fibre fragments with diameters ranging from the nanometre to the micron scale. MFC suspensions of a few percent solids content show very high viscosity at low shear rates, but also very significant shear thinning behaviour, rapid viscosity recovery after shear and high filtration resistance. MFC added to paper furnishes at up to 5% by weight functions as a strength additive, enabling increases in mineral filler content, improvements in paper properties, reductions in weight and cost savings across a wide range of paper and board grades. As a complementary technology to pulp refining, addition of MFC offers process flexibility as well as improved wet web strength and runnability, reduced air permeability and increased z-direction strength. Although the fine fibrils of MFC do not dewater easily on their own, when added at low levels to paper their effect on machine drainage can be managed without loss of paper machine speed. In recent years, MFC has attracted much interest as a coating material. Layers or films of pure MFC show near-zero air permeability, high resistance to oil and grease and an effective barrier to organic vapours and oxygen. Mixtures of mineral particles and as little as 15% MFC provide an effective surface for water-intensive printing techniques such as flexography and inkjet. Application of MFC suspensions after the wet line of a papermachine has been demonstrated as a practical solution to obtain coatings, exploiting the rheological behaviour of the MFC to achieve excellent holdout onto a poorly-consolidated sheet, and using the vacuum and press sections of the machine to remove excess water. Further development and commercialisation of this technology, together with low cost MFC production and improved product characterisation, should ensure the continued growth of its use in the paper and board industry.

The wet-web strength of paper immediately after the press section of a paper machine is a critical factor in determining machine runnability. However, it is difficult to determine at commercial scale, because the web has to be broken and production interrupted in order to obtain a sample for measurement. The use of microfibrillated cellulose (MFC) is believed to increase wet-web strength, as it has allowed filler level increases of 10% or more on many commercial paper machines. In this paper, we describe a laboratory method for estimating the effect of MFC on wet sheet strength after pressing, as well as actual measurements of wet-web strength from a pilot paper machine trial. These experiments have demonstrated the positive effect of MFC. At solids contents in the range typically observed after pressing, sheets with MFC at fixed filler content are significantly stronger, but also wetter, than those without it. When the use of MFC is combined with a typical increase in filler content, the wet web remains slightly stronger, but also becomes drier than the reference condition. These results are compatible with the theory put forward by van de Ven that wet-web strength is mainly a result of friction between entangled fibers, and they also suggest that the presence of MFC increases this friction.

When pulp and minerals are co-processed in suspension, the mineral acts as a grinding aid, allowing cost-effective production of mineral/microfibrillated cellulose (MFC) composite materials. This processing uses robust milling equipment and is practiced at industrial scale. The resulting products can be used in many applications, including as wet- and dry-strength aids in paper and board production. Previously, we have reported that use of these MFC composite materials in fiber-based applications allow generally improved wet and dry mechanical properties with concomitant opportunities for cost savings, property improvements, or grade developments. Mineral/MFC composites made with recycled pulp feedstocks were shown to offer at least equivalent strength aid performance to composites made using virgin fibers. Selection of mineral and fiber allows preparation of mineral/MFC composites with a range of properties. For example, the viscosity of such formulations was shown to be controlled by the shape factor of the mineral chosen, effective barrier formulations were prepared, and mineral/MFC composites with graphite as the mineral were prepared. High-solids mineral/MFC composites were prepared at 75% total solids (37% fibril solids). When resuspended and used for papermaking, these high-solids products gave equivalent performance to never-dried controls.

A wide variety of wood and non-wood cellulosic fibre sources were used as a feed to produce microfibrillated cellulose (MFC) using a grinding process. Nanopaper was formed using this product, and the tensile index was measured. The hemicellulose content of the feed fibres was measured, and was found to correlate with the production of finer microfibrils and a higher MFC tensile strength. The correlation with tensile strength was improved by the inclusion of a measurement of the MFC particle lengths as measured by a fibre image analyser, with the resulting relation fitting a modified Page Equation. It was hypothesised that the frequency of flaws in the feed fibre cross-section influences the length of the MFC particles produced, and so the zero-span tensile index of the fibres was measured as a proxy for this since it forces cross-sectional fibre breakage. The fibre zero-span tensile index was found to correlate with MFC particle length and so was used in its place in the equation. The resultant equation can predict MFC tensile strength from zero-span tensile index and hemicellulose content measurements of cellulosic fibres and can aid in optimising feedstock selection for mechanical MFC production processes.

Microfibrillated cellulose (MFC) is a highly expanded, high surface area networked form of cellulose-based reinforcement. Due to the poor compatibility of cellulose with most common apolar thermoplastic matrices, the production of cellulose-reinforced composites in industry is currently limited to polar materials. In this study, a facile water-based chemistry, based on the reaction of MFC with tannic acid and subsequent functionalisation with an alkyl amine, is used to render the surface of the MFC fibrils hydrophobic and enhance the dispersion of the cellulose-based filler into an apolar thermoplastic matrix. The level of dispersion of the compatibilized MFC reinforced composites was evaluated using Time of Flight Secondary Ion Mass Spectrometry and multi-channel Spectral Confocal Laser Scanning Microscopy. The agglomeration of cellulosic filler within the composites was reduced by functionalising the surface of the MFC fibrils with tannic acid and octadecylamine. The resulting composites exhibited an increase in modulus at a high cellulose content. Despite the dispersion of a large portion of the functionalised filler, the presence of some remaining aggregates affected the impact properties of the composites produced.

AbstractWe describe the design and development of an elastomeric sealant for improved zonal isolation. The sealant is intended for use during primary cementing, and has been formulated so that it can be pumped as part of the cement train and placed around the shoe of a casing. In this way reliable isolation at key points in the well can be achieved without incurring excessive costs. The mechanical property specifications of the sealant have been determined using stress analysis; we show how a sufficiently deformable material remains effectively confined by the wellbore and thus cannot be subjected to tensile stresses that could cause its failure, and that it needs to be held in a state of compressive stress in order to prevent gas leakage. By applying pressure to the sealant during curing and allowing it to expand thermally afterwards, a suitable state of compression can in principle be generated. The necessary control over the rheology, density and curing time of the sealant to enable its reliable placement has been achieved. The effect of the initial stress state and the performance of the sealant compared with cement-based materials are demonstrated in a full-scale test.

Raman spectroscopy has been used to follow the hydration of one of the principal components of Ordinary Portland Cement (OPC) clinkers, tricalcium aluminate, both in the absence and in the presence of calcium sulfate. Direct in-situ analysis of the hydrating paste surface was possible. Spectra were recorded regularly during the first 24 hours of hydration, and then systematically after hydration periods of up to 28 days. X-Ray diffraction was performed to confirm sample identity, firstly after 24 hours and then regularly in coordination with Raman analysis. Hydration in the absence of sulfate was rapid and led to the initial formation of C(4)AH(19) and subsequently C(3)AH(6). Characteristic changes were seen in the Raman spectra and the products' identities confirmed by XRD. Hydration in the presence of sulfate led to very rapid ettringite (AFt) formation, with the first evidence of ettringite formation within 3 minutes. Ettringite gradually converted to monosulfate ( AFm), with the re-formation of traces of gypsum at high sulfate contents. Ettringite was formed at the expense of C(4)AH(19). The level of C(4)AH(19) formed diminished greatly with increasing sulfate content. Care was taken throughout the study to exclude carbon dioxide, thus minimising formation of various carbonate species, which could also be readily distinguished by Raman spectroscopy. By combining the results obtained using the well-established technique of X-ray diffraction with Raman spectroscopy, in-situ characterisation of hydrating pastes has been achieved in real-time. In addition to demonstrating the suitability of Raman spectroscopy for analysis of these systems this study should aid the understanding of tricalcium aluminate hydration and the formation of ettringite and monosulfate.

Raman spectroscopy has been used to follow the hydration of C(3)A and C(4)AF, two of the principal components of ordinary Portland cement (OPC), in the absence and presence of calcium sulphate ( gypsum). Raman spectroscopy enabled in situ, real time analysis of the hydrating pastes. Analysis of the pastes by X-ray diffraction complemented the Raman data and confirmed sample composition. Subtle changes in the Raman spectra of the different pastes illuminated differences in hydration behaviour between C(3)A and C(4)AF. The similarities and differences between the various systems are discussed. The influence of carbon dioxide on the hydration products has also received attention.

A new phase diagram is reported for the CaOAl2O3SiO2H2O (CASH) system at 200°C. This system is rare in nature but has applications in cementing geothermal and deep oil wells. The phase diagram was constructed by synthesising a range of hydroceramics with CASH assemblages from oilwell cement, silica flour (quartz) and alumina (corundum). A hydroceramic is defined as any ceramic material incorporating water as H2O or OH. At 200°C, gyrolite, hillebrandite, jaffeite, portlandite, quartz, 11Å tobermorite, xonotlite, hibschite and katoite were observed as product phases. The mineral assemblages produced the following three-phase triangles in the CaOAl2O3SiO2 diagram: Gyr+Qtz+Xon; Crn+Tob+Xon; Crn+Hib+Xon; Crn+Hib+Jaf; Crn+Jaf+Kat; Hib+Jaf+Por; Hib+Jaf+Xon; and two reactions are found to be in progress at 200°C. When alumina is present in the reaction mixture, the thermal stability of tobermorite is extended to higher temperature, and the crystallinity of tobermorite and xonotlite enhanced.

Synchrotron energy dispersive diffraction has been used to monitor the mineral transformations which occur in the paste hydration of brownmillerite Ca2AlFeO5 in a closed hydrothermal environment at temperatures in the range 30 to 150 °C. In the absence of sulfate brownmillerite reacts rapidly to form a metastable hexagonal hydrate with a basal spacing of 1.07 nm. As temperature increases the metastable hydrate transforms to the stable hydrogarnet phase Ca3(Al,Fe)2(OH)12 with an Al/(Al + Fe) ratio of about 0.4. The lack of iron in the metastable hydrate suggests a through-solution mechanism while the iron content of the hydrogarnet indicates it must form on the surface of the brownmillerite, probably in contact with the Fe-rich residue remaining after dissolution. The addition of gypsum CaSO4·2H2O increases the rate of brownmillerite hydration. Ettringite Ca6Al2(SO4)3(OH)12·26 H2O is formed at ambient temperature and is replaced by calcium aluminium monosulfate-14 hydrate Ca4Al2O6(SO4)·14H2O at elevated temperatures (70, 100 and 150 °C). Transient increases in gypsum accompany this transformation and all three phases can co-exist at 70 °C. Monosulfate-14 is stable at 150 °C. Increases in brownmillerite peak intensities accompany the conversion of ettringite to monosulfate and are a result of sedimentation. This has implications for paste rheology and slurry design in oilwell cements at elevated temperatures.