Kraft Fibers Research Articles

Flexural behaviour and post-cracking performance of polypropylene fibre-reinforced waste cardboard blended concrete

The requalification of recycled materials has become of significance owing to a global shift towards net zero emissions and the severe environmental impact of misused recyclable waste. Cardboard and polypropylene have evolved into significant waste products, and the purpose of the study was to focus on the repurposing of both waste materials in determining the structural behaviour of an eco-efficient fibre-reinforced waste concrete. The study extended upon the findings of a precursor study in the development of an eco-efficient fibre-reinforced waste concrete mix. Finely processed municipally collected waste cardboard and recycled polypropylene macro-fibres were incorporated into a concrete mix design for which an experimental program was realised. To achieve this, uniaxial compressive strength, modulus of rupture, modulus of elasticity, and indirect tensile strength of the waste and reference mixtures were determined for 7- and 28-day intervals. Crack mouth open displacement testing was achieved to assess the post-cracking response, and retaining wall beams were prepared and loaded to determine the efficacy of the concrete mixture for low load-bearing structures. Mechanical and post-cracking properties of the hybrid waste concrete underscored excellent performance in comparison to other waste fibre-reinforced concrete mixtures, and superior to those blended with similar kraft fibre volume fractions. Moreover, the structural performance of beams cast from the hybrid mixture closely matched those of the reference mixture, emphasising the viability of the mixture and the role waste materials have in the construction and building industry.

Assessment of the Mechanical and Microstructural Performance of Waste Kraft Fibre Reinforced Cement Composite Incorporating Sustainable Eco-Friendly Additives

This study investigates the influence of limestone powder and metakaolin as sustainable eco-friendly additives on the properties and behavior of cementitious composite boards, with a focus on mechanical strength, physical properties, and microstructural characteristics. The experimental investigation begins with the characterization of the raw materials, including limestone powder, and metakaolin, to assess their particle sizes, elemental composition, and microstructural features. Cement composite boards were fabricated using an innovatively developed lab-simulated vacuum dewatering process, by varying the proportions of limestone powder and metakaolin as partial replacements for cement, along with waste kraft fibres as reinforcement. Mechanical testing was conducted to evaluate the flexural strength and behaviour of the composite boards according to standardized procedures. A microstructural analysis was performed using scanning electron microscopy (SEM) to examine the effect of additives on the cementitious matrix, fibrematrix interaction, and hydration products. The findings from the experimental study reveal insights into the influence of limestone powder and metakaolin on the mechanical properties and microstructure of waste kraft fibre-reinforced cement composite boards. Our analysis of the results shows that adding 9% limestone powder as partial cement replacement produces a 24% and 50% enhancement in flexural strength at 7 and 28 days of hydration, while that of metakaolin as partial cement replacement was optimum at 6% with an enhancement of 4% and 36%, respectively, at 7 and 28 days of hydration. The implications of these findings for the development of sustainable cementitious composite are discussed, including the potential benefits of using limestone powder and metakaolin as supplementary cementitious materials in waste kraft fibre-reinforced cement composite boards. Finally, recommendations for optimizing additive proportions are also provided to enhance the understanding and application of these materials in the construction and building industries.

Model systems for clarifying the effects of surface modification on fibre–fibre joint strength and paper mechanical properties

The growing demand for sustainable products has spurred research into renewable materials, with cellulose-based materials emerging as prominent candidates due to their exceptional properties, abundance, and wide-ranging applications. In this context, there is a need to develop a better fundamental understanding of cellulose interactions such that we can continue to design and improve sustainable materials. Individual interactions can be difficult to assess in bulk fibre-based materials and therefore cellulose model materials have become indispensable tools for researchers as they can facilitate the study of cellulose interactions at a molecular level enabling the design of sustainable materials with enhanced properties.This study presents a new methodology for studying the effects of surface treatments on the individual fibre–fibre joint strength using wet-spun cellulose nanofiber (CNF) filaments as model materials. The Layer-by-Layer assembly technique is used to modify the surface chemistry of the model materials as well as bleached and unbleached hardwood Kraft fibres, demonstrating its potential to enhance adhesive properties and overall mechanical performance of papers made from these fibres. The study further explores the impact of increasing network density through wet-pressing during paper preparation, showcasing a comprehensive approach to molecularly tailor fibre-based materials to achieve superior mechanical properties. The proposed methodology provides a time-efficient evaluation of chemical additives in paper preparation.

Enhancing subsequent kraft fiber dewatering properties by using fiber polyamide-epichlorohydrin (PAE) treatment to prepare a dry pulp product,

The energy needed for the dewatering and drying of wet paper web represents around half of the energy consumption of papermaking processes. The present work examined whether the dewatering and drying of paper could be enhanced during a previous pulp drying process by pretreating the fibers with polyamide-epichlorohydrin (PAE). According to the hypothesis, the cured PAE restrains swelling and water absorption of water-wetted fibers by forming a fiber-bound, self-crosslinked polymer-network on the fiber surfaces. The hypothesis was tested by adding PAE to never-dried kraft pulp slurry followed by pulp thickening, drying, and final curing of the PAE-resin. After this, the PAE-treated fibers were dispersed in water, and their water retention values (WRV) and Shopper-Riegler values (○SR) were measured. The PAE pretreatments notably decreased the fibers´ WRV and ○SR, indicating improved water removal of paper web in the paper machine forming and drying section. Compared to chemical crosslinking pretreatments, which also can be used to decrease fibers WRV and ○SR-value, a notable advantage of PAE-pretreatment is milder required curing conditions of the PAE, which makes implementation of the method easier in practice. Due to decreased fiber-to-fiber bonding capability, the PAE-treated specialty fibers could take advantage especially as a bulking aid of paperboard, tissue, and absorbent materials.

FABRICATION OF HIGH STRENGTH PAPER FROM DIFFERENT TYPES OF PHOSPHORYLATED FIBERS USING HOT PRESSING AND FORMING AGENTS

Phosphorylated fibers offer a broad range of applications, particularly in thermal insulation, notably with wood fibers, provided they exhibit improved mechanical characteristics. Despite encountering challenges in applying traditional papermaking methods, the creation of paper or board sheets with phosphorylated pulp fibers remains a challenge. Findings suggest that phosphorylation-modified fibers show increased roughness. Moreover, in comparison with unbeaten kraft sheets (KF) and thermomechanical pulp sheets (TMP), those made from phosphorylated kraft fibers (PKF), using a cationic coagulant and a flocculant, demonstrate significant enhancements in burst index, break index, and tensile energy absorption by 2.12 times, 1.7 times, and 2.77 times, respectively. Similarly, phosphorylated TMP sheets, prepared with a dual polymeric system (coagulant/flocculant), exhibit improvements of 1.42 times, 1.33 times, and 1.82 times, respectively, in these properties. The study emphasizes the ameliorating effect of cationic polymeric agents on the charge impact of phosphorylated fibers on overall sheet quality, while also highlighting the substantial influence of hot-pressing lignin-containing paper on all determined physical properties.

Influence of density and chemical additives on paper mechanical properties

In this work we have investigated the effect of surface modification of fibres on the overall mechanical properties of high-density papers. Paper sheets were prepared by a combination of heat-pressing and polyelectrolyte Layer-by-Layer (LbL) modification of different softwood fibres. LbLs of Polyallylamine Hydrochloride (PAH) and Hyaluronic Acid (HA) were adsorbed onto unbleached kraft fibres and bleached Chemo-ThermoMechanical Pulp (CTMP) to improve the strength of the fibre–fibre joints in papers made from these fibres. Additionally, different sheet-making procedures were used to prepare a range of network densities with different degrees of fibre–fibre interaction in the system. The results demonstrate that interfacial adhesion within fibre–fibre joints plays a pivotal role in the network's performance, even at higher paper densities. Hygroexpansion measurements and fracture zone imaging with Scanning Electron Microscopy (SEM) further support the claim that stronger interactions between the fibres allow for a better utilisation of the inherent fibre properties. Surface treatments and network densification significantly improved the paper sheets' mechanical properties. Specifically, LbL-treatments alone increased specific stiffness up to 60% and specific strength by over 100%. This improvement is linked to the build-up of residual stresses during drying. Due to a high interaction between the fibres during water removal the fibres become constrained, leading to increased stretching of fibre segments. Strengthened fibre joints intensify this constraint, further increasing the stretch and, consequently, the paper's strength.

Modeling and simulation of anisotropic cross-linked cellulose fiber networks with an out-of-plane topography

Non-woven cellulose fiber networks of low areal density are widely used in many industrial applications and consumer products. A discrete element method (DEM) modeling framework is advanced to simulate the formation of strongly anisotropic cellulose fiber network sheets in the dilute limit with simplified hydrodynamic and hydroelastic interactions. Our modeling accounts for in-plane fiber orientation and viscous drag indirectly by using theories developed by Niskanen (2018 Fundamentals of Papermaking, Trans. 9th Pulp and Paper Fundamental Research Symp. Cambridge, 1989 (FRC) pp 275–308) and Cox (1970 J. Fluid Mech. 44 791–810) respectively. Networks formed on a patterned and flat substrate are simulated for different fiber types, and their tensile response is used to assess the influence of the out-of-plane topographical pattern, specifically, on their stiffness and strength. Sheets with the same grammage and thickness, but composed with a higher fraction of softwood fiber (longer fibers with large diameter), have higher strength and higher strain to failure compared to sheets made from hardwood fibers (short fibers with small diameter). However, varying the fiber fraction produces only an insignificant variation in the initial sheet stiffness. The above simulation predictions are confirmed experimentally for sheets comprised of fibers with different ratios of Eucalyptus kraft and Northern Bleached Softwood Kraft fibers. Sheets with out-of-plane topography show an unsymmetric mass distribution, lower tensile stiffness, and lower tensile strength compared to those formed on a flat substrate. The additional fiber deformation modes activated by the out-of-plane topography, such as bending and twisting, explain these differences in the sheet mechanical characteristics.

Sustainable Materials from Organosolv Fibers and Lignin, Kraft Fibers, and Their Blends.

The aim of this study was to investigate new materials from organosolv fibers, organosolv lignin, kraft fibers, and their blends. The organosolv fibers showed reprecipitated lignin on the surface, a comparably low fiber length of 0.565 mm on average, and a high fines content of 82.3%. Handsheets were formed and thermopressed at 175 °C and 50 MPa, yielding dense materials (1050-1100 kg/m3) with properties different to that of regular paper products. The thermopressing of organosolv fibers alone produced materials with similar or better tensile strength (σb = 18.6 MPa) and stiffness (E* = 2.8 GPa) to the softwood Kraft reference pulp (σb = 14.8 MPa, E* = 1.8 GPa). The surface morphology was also smoother with fewer cavities. As a result, the thermopressed organosolv fibers exhibited higher hydrophobicity (contact angle > 95°) and had the lowest overall water uptake. Combinations of Kraft fibers with organosolv fibers or organosolv lignin showed reduced wetting and a higher density than the Kraft fibers alone. Furthermore, the addition of organosolv lignin to Kraft fibers greatly improved tensile stiffness and strength (σb = 23.8 MPa, E* = 10.5 GPa), likely due to the lignin acting as a binder to the fiber network. In conclusion, new thermopressed materials were developed and tested, which show promising potential for sustainable fiber materials with improved water resistance.

Optimizing the Mechanical Properties of Cement Composite Boards Reinforced with Cellulose Pulp and Bamboo Fibers for Building Applications in Low-Cost Housing Estates.

Africa is the third-richest continent in the world in terms of bamboo species. Despite these laudable natural resources, most African countries still use asbestos cement board as one of their major building materials. This is chiefly due to the high cost of equipment and technologies associated with non-asbestos-fiber cement board production. The current research seeks to underscore the possibility of utilizing these massive continent resources for non-asbestos-fiber cement board production by employing the existing production process in the asbestos cement industries via an innovatively developed laboratory-simulated Hatschek process. Non-asbestos-fiber cement boards incorporating kraft and bamboo fibers were successfully produced in the laboratory using this innovative method based on Hatschek technology, with natural fibre addition in the range of 2-6 wt.%. Experimental results revealed that the Flexural strength and deflection of the board improved significantly, producing optimum values of 10.41 MPa and 2.0 mm, respectively for composite board reinforced with 10 wt.% and 6 wt.% of kraft pulp and bamboo fibers, respectively. The SEM morphology of the fractured surfaces revealed the mode of composite fracture as well as good interaction at the fiber-matrix interface. Overall, the mechanical properties of the developed composite boards satisfy the minimum requirements of relevant standards based on fiber cement flat sheets and can be employed for internal building applications in low-cost housing estates in developing countries. The outcome of this research indicates that the current industrial production process based on Hatschek technology can be employed for non-asbestos-fiber cement board production using the studied natural fiber.

Click chemistry modifications for the selective crosslinking of wood pulp fibers - effect on the physical and mechanical properties of paper.

The Cu(i)-catalyzed Huisgen cycloaddition click chemistry reaction is of particular interest in the production of paper sheets or natural fiber composites since it leads to the formation of chemically stable bonds between two fibers. This study focuses on the click chemistry modification of kraft pulp fibers. We based our approach on prior research that treated kraft fibers using click chemistry, including propargylation and tosylation reactions. Our focus was on enhancing these treatments to achieve better final sheet properties. After the azidation of tosylated fibers, the crosslinking is carried out with and without a catalyst using water as a solvent to form enhanced kraft fiber sheets. The chemical characterization and the mechanical properties of fibers obtained at intermediate stages confirmed the presence of various functions on the surface of the modified fibers, with a very high degree of substitution and the inter-fiber cross-linking by click chemistry. The presence of inter-fibers covalent bonds led to significant improvements in the mechanical strength and tensile stiffness of the sheets.

Organic Hydromulches in Young Olive Trees in Pots: Effects on Soil and Plant Parameters

Organic hydromulches (liquid spray-on mulches) have been used traditionally in land rehabilitation, mainly to mitigate post-fire runoff and erosion. However, in recent years, a new application of these materials as an eco-friendly alternative to the widely used polyethylene mulch, both in vegetable and woody crops, has been studyied. This work analyzes the effects of six hydromulches, based on organic by-products, on different soil parameters (water content, temperature, and CO2 flux), plant–water relations (stem water potential, leaf gas exchange, and leaf temperature), and the growth (trunk diameter) of young olive trees planted in large pots in the open field over a 2-year trial. The hydromulches tested were: rice husk (RH), rice husk with linen oil (RHL), mushroom substrate (MS), wheat straw (WS), pistachio (PW), and vineyard (VW) pruning wood chips, mixed with different additives (gypsum, recycled paper paste, and Kraft fiber). A non-mulched manual weeding control (NM) was included. The results indicated that hydromulches, in comparison with NM, resulted in increased volumetric soil water content (on average, 22.9% in hydromulches and 19.5% in NM), reduced soil temperature fluctuations (4.97 °C in hydromulches and 6.13 °C in NM), and increased soil CO2 fluxes (0.80 and 0.49 g CO2 m−2 h−1, respectively). Although the differences in the soil water content did not have an obvious effect on the plant–water status, crop growth was reduced in NM (≈23% lower than PW, MS, RHL, and WS), suggesting that vegetative growth, especially in young olive trees, is extremely sensitive to water deficit. The overall study leads to considering hydromulches as a good alternative to mulching in large pots, especially PW, which would be useful for nursery crops before their final establishment in the field.

Improving Recycled Paper Materials through the Incorporation of Hemp, Wood Virgin Cellulose Fibers, and Nanofibers

A significant increase in the consumption of recycled fiber products has been observed worldwide, and the industry is forced to solve the challenges of recycled fiber quality and add strength agents and/or virgin fibers to reach sufficient properties. In order to investigate whether the mechanical and air permeability properties of waste fiber (WF) material can be significantly improved by adding wood kraft fibers (KF), hemp soda fibers (HF), and ammonium persulfate oxidated cellulose nanofibrils (CNF), different fiber blends were prepared and tested. Results revealed the excellence of hemp fibers over wood fibers regarding the improvement of WF products. The results of WF after the addition of 10% mixed fibers (KF + HF) were higher than the results of a 50% KF addition. The impact of CNF depended on fiber composition and properties. A formula for modeling the CNF impact on different fiber compositions was proposed. Obtained fiber material samples showed suitability for home composting, thus contributing to the goals of the European Green Deal regarding reducing landfill waste and the development of cleaner products.

Evaluation of kraft pulp, fibre and paper traits of interspecific hybrid Corymbia clones at four years

Two interspecific Corymbia hybrid clones, ITC 2081 & CH440 (Corymbia torelliana × C. citriodora subsp. variegata), were evaluated for growth, pulp, fibre and paper properties at four years in comparison to an E. camaldulensis (Ec) clone. Wood basic density and fibre traits were estimated from increment core samples and logs were chipped for evaluating pulp and paper traits. The Corymbia clones had comparable growth, but wood basic density was 12% higher than the Ec clone. The fibre traits were superior, with 24% larger fibre in the Corymbia hybrid clones, and 2% higher pulp yield (Kappa number 17) than the Ec clone. The Corymbia hybrid clones had comparable unbleached hand sheet brightness of the Ec clone but were superior in parameters like sheet stiffness, thickness, burst and tear factor. While Ec clones have attained the threshold of pulp wood traits improvement, the new Corymbia hybrids have demonstrated potential for improving the profitability of pulp industries in India.

Harnessing total chemical-free paper and packaging materials barrier properties by mechanical modification of cellulosic fibers for food security and environmental sustainability

Surging interest in finding sustainable alternatives for single-use plastics has galvanized research into cellulosic fiber-based paper and packaging materials. This investigation examines mechanical (refining & calendering) approaches to enhance paper's barrier properties comprising Southern bleached hardwood kraft (SBHK) and Southern bleached softwood kraft (SBSK) fibers. With increased refining intensity followed by calendering, paper thickness decreases while the apparent density increases. The refining process also generates more fibrils and fines, as reflected by reduced pulp freeness. Air resistance increases significantly due to denser fiber networks and reduced porosity. Refining also improves the water vapor transmission rate (WVTR) and oil & grease resistance (OGR). A 48 % reduction in WVTR and a Kit "9″ rating for OGR were observed in SBHK paper sheets refined at 16000 revolution. Notably, refining modifies cellulose fiber morphology, promoting 59 % and 94 % external fibrillation in SBSK and SBHK fibers, respectively. This change facilitates a more compact fiber arrangement, enhancing barrier properties. XRD patterns show an initial increase in cellulose crystallinity with refining, decreasing at a higher revolution of refining. SEM analysis reveals decreased surface roughness and pore fraction post-calendering, enhancing air and OGR. In a relative sense, hardwood fibers showed higher barrier performance than softwood fibers. Our work demonstrates mechanical modifications of fibers and paper web can effectively tune paper barrier performance such as WVTR, OGR, and air/oxygen resistance.

Influence of temperature and pressure during thermoforming of softwood pulp

In this study, the influence of thermoforming conditions on the resulting material properties was investigated, which aimed at developing advanced wood-fiber-based materials for the replacement of fossil plastics. Two bleached softwood pulps were studied, i.e., northern bleached softwood Kraft pulp (NBSK) and chemi-thermomechanical softwood pulp (CTMP). The thermoforming conditions were varied between 2–100 MPa and 150–200 °C, while pressing sheets of 500 g/m² for 10 min to represent thin-walled packaging more closely. As our results showed, the temperature had a more pronounced effect on the CTMP substrates than on the Kraft pulp. This was explained by the greater abundance of lignin and hemicelluloses, while fibrillar dimensions and the fines content may play a role in addition. Moreover, the CTMP exhibited an optimum in terms of tensile strength at intermediate thermoforming pressure. This effect was attributed to two counteracting effects: 1) Improved fiber adhesion due to enhanced densification, and 2) embrittlement caused by the loss of extensibility. High temperatures likely softened the lignin, enabling fiber collapse and a tighter packing. For the Kraft substrates, the tensile strength increased linearly with density. Both pulps showed reduced wetting at elevated thermoforming temperature and pressure, which was attributed to hornification and densification effects. Here, the effect of temperature was again more pronounced for CTMP than for the Kraft fibers. It was concluded that the thermoforming temperature and pressure strongly affected the properties of the final material. The chemical composition of the pulps will distinctly affect their response to thermoforming, which could be useful for tailoring cellulose-based replacements for packaging products.

Economic and environmental optimisation of waste cardboard kraft fibres in concrete using nondominated sorting genetic algorithm

The depletion of natural resources is accelerating due to increased construction activities across the world. The search for alternative materials used in concrete is becoming a prominent measure to reduce greenhouse gas (GHG) emissions in the construction industry. Cement in concrete produces 4–8% of all GHG emissions annually worldwide. Alternative materials such as waste cardboard provide an opportunity to be utilised further in such applications. This study focuses on using nondominated sorting genetic algorithm (NSGA-II) to optimise the economic cost and GHG emissions of concrete incorporating recycled waste cardboard as a partial cement substitute. The multi-objective optimisation solutions produced three key regions that corresponded with trade-offs between the lowest costs, carbon emissions or a combination of both. Region 1 was the most economical but created the most carbon emissions. Region 2 was a compromise between both economical, and environmental factors and region 3 demonstrated the lowest carbon emissions but also produced the highest costs. These regions produced three mix designs which were experimentally analysed for their compressive strength. The results indicated a cost increase of 17, 27 and 36% for three key optimised regions. This is primarily due to increased material costs and further manufacturing requirements when converting waste cardboard into kraft fibres (KFs). Increasing the amount of KFs then reduced the compressive strength from 36 to 56%. However, there was a 7, 18 and 28% GHG emission saving when KFs partially replaced cement.

Obtaining and Microstructural Study of a Multifunctional Highly Phosphorylated Starch

AbstractThis study reports the phosphorylation of starch by a method used for kraft fibers. Energy dispersive X‐ray (EDX) analysis shows that this product contains 20% phosphorus and 9% nitrogen. The corresponding degrees of substitution (DS), on the anhydroglucose repeating unit (AGU), by phosphorus‐containing (DSP) and nitrogen‐containing (DSN) groups are 2.32 and 1.38, respectively. The microstructural characterization techniques (13C and 31P NMR, ATR‐FTIR), indicate the existence of several functional groups simply linked or acting as bridges between the chains. The degree of charge (4446 mmol kg−1), determined by potentiometry, is lower than that calculated theoretically (6617 mmol kg−1). This is due to a transformation of the phosphate groups (─O─PO3H2) into (─O─PO3H─) forming inter‐chain bridges. The viscosimetric increment varies very little with concentration, indicating that the study is dealing with particles made up of highly cross‐linked polysaccharide chains, whose hydrodynamic volume expansion is strongly restricted. The thermogravimetric study, mass loss as a function of temperature, generates levoglucosan as the majority product. It indicates the persistence of AGU despite modification reactions. By pooling all the data, the study is able to propose an approximate microstructure. Application tests for fertilizer, adsorbent, flame retardant, water retainer, and gelling agent are conclusive.

Effect of chemical crosslinking on the biodegradation rate of kraft paper

Wood-based paper fibers are inherently biodegradable. In contact with moist soil and in compost, papermaking fibers are readily broken down by soil microbes. Resistance to biodegradation is needed, as paper is used for special applications such as mulching in agriculture and forestry, the coating of construction materials, and for packing and wrapping under conditions where packaging materials may be exposed to contact with moist soil or other type microbial active contamination. A preceding study showed that paper chemical crosslinking with glyoxal, citric acid (CA), or methylated 1,3-dimethylol-4,5-dihydroxyethylene urea (mDMDHEU) results in substantially improved paper wet strength and lower paper water absorbency. The present study examined the efficiency of chemical crosslinking treatments with CA and with mDMDHEU to decrease the biodegradation rate of laboratory paper sheets and a sack paper, both made of kraft fibers. The biodegradation was examined using a 48-h enzymatic degradation test and a 2-month soil burial test. The results indicate that chemical crosslinking is an effective non-biocidal method for making sulphate kraft paper more resistant to biodegradation. In some end-uses, improved resistance to biodegradation, along with improved paper wet performance, can enhance paper performance comparable to plastic films.

High consistency enzymatic pretreatment of eucalyptus and softwood kraft fibres for regenerated fibre products

Sustainability of regenerated cellulosic fibres could be improved by using paper grade pulp instead of dissolving pulp as a raw material in the fibre spinning process. However, the use of paper grade pulp calls for adjustment of the molar mass distribution (MMD) prior to dissolution to obtain good solubility and spinnability. The objective of this work was to adjust MMD of softwood and eucalyptus kraft pulps by enzymatic treatments at high pulp consistency. The reduction of the MMD of eucalyptus kraft pulp was found to require a nearly 30-fold higher dose of endoglucanase compared to the treatment of softwood pulp. Interestingly, when xylanase was used in combination with endoglucanase to treat eucalyptus kraft pulp, 27% of the xylan was dissolved and the required endoglucanase dose could be decreased from 0.57 to 0.06 mg/g. The endoglucanase dose could be further decreased to 0.028 mg/g when 67% of xylan was removed chemically before the enzymatic treatment. This suggests that xylan hinders endoglucanase action on eucalyptus kraft pulp. For softwood pulp, the addition of xylanase and mannanase had only a minor impact on the treatment efficiency. The different processabilities of softwood and eucalyptus kraft pulps are suggested to originate from the deviating cellulose accessibility which is affected by the fibre structures as well as their hemicellulose composition and localisation. The effect of the treatment consistency was further studied with softwood kraft pulp. Treatment at high consistency clearly enhanced the endoglucanase action whereas the effect of solid content on the hemicellulase action was modest.

The durability performance of waste cardboard kraft fibre reinforced concrete

Despite the high recycling rate of cardboard, a significant amount of this material is disposed of in landfill areas. The conversion of cardboard waste into kraft fibres (KFs) offers potential sustainability benefits when used in the building and construction industry. This study comprehensively analyses the durability of KF reinforced concrete as a partial cement substitution. Durability testing was conducted, exploring the composites microstructure when integrating KFs derived from waste cardboard. Fibre and matrix modification techniques were utilised via silica fume (SF) and metakaolin (MK), respectively. Porosity analysis of the novel composites demonstrated connecting microstructural system, enhancing the knowledge of durable aspects of potential service life of the composites. SF reduced the water permeability of the novel composites as demonstrated via water absorption and immersion testing. At one year, there was a reduction of chloride ion transference for all fibre composites. Composites were aged via wet and dry cycles, then tested for their compressive and tensile strength at each interval. Compressive strength of all samples peaked at 60- 80 day-cycles. Fibre Matrix modified composites demonstrated a tensile strength of 2.5 MPa when subjected to 100 day-cycles, with the control having 2.7 MPa.