Properties Of Paper Sheets Research Articles

Characterization of Asoka (Saraca Indica L.) branch wood for pulp and paper manufacturing

Asoka (Saraca indica L.) branch wood was evaluated for its chemical composition, morphological features, kraft pulping behavior, and physical properties. The Asoka used in this study contained low amounts of cellulose and hemicellulose, but higher amounts of lignin and ash. It was found that the morphological indices of Asoka branch wood were mostly adequate for pulping and papermaking. The pulping of this wood was performed using chemi-mechanical pulping (CMP), conventional kraft pulping, and soda pulping processes under different conditions, i.e., active alkali and anthraquinone (AQ) addition. The results showed that alkaline pupling and CMP provided low screened yield values. Acceptable kappa numbers and reject levels were obtained at 22% active alkali of soda and kraft-AQ pulpings. CMP pulp showed higher brightness and screened yield than that of alkaline pulps. Alkaline pulpings of Asoka branch wood provided slightly different strength properties of paper sheets than those of CMP pulp. Based on the findings, it can be concluded that Asoka branch wood is more suitable as a raw material for mechanical pulping than it is for alkaline pulping.

Influence of TEMPO-oxidation on pulp fiber chemistry, morphology and mechanical paper sheet properties

In this contribution, we report on the TEMPO-mediated oxidation of pulp fibers used in the general context of papermaking and for the future design of tailor-made paper in advanced applications. We focus in our studies on properties of TEMPO-oxidized pulp fibers to explain the characteristics of the paper made thereof. 13C solid-state NMR analysis reveals that in particular amorphous regions of the fibers are being chemically oxidized, while at the same time the crystalline regions of the fibers are not significantly affected. Investigation of the fiber morphology before and after oxidation shows that the fiber length is not changed, yet the fibers do exhibit an increase in width if in contact with water, which is attributed to an increase in fiber swelling. In addition, fibrillation decreases due to the oxidative removal of loosely bound fines and fibrils, rendering the surface of the resulting oxidized fibers much smoother in comparison to the original fibers. Finally, we observe that both, dry and wet tensile strengths are also higher for paper made of oxidized fibers, most likely due to cross linkable aldehyde groups formed during oxidation (i.e. hemiacetal bond formation in the sheet during thermal drying). Our results of the oxidation of paper fibers thus offer a systematic study helpful for the design of tailor-made paper useful in several applications where a fiber-modification with fiber-immobilized functional motifs is crucial, such as for example in paper-based microfluidic sensors (µPADs) or lab-on a chip-devices.

Nanofibers isolated from unbleached date palm residues pulps and their use for paper coating

In the current work, cellulose nanofibers (CNF) were isolated from unbleached kraft pulps of date palm fruit stalks (DPFS) and date palm rachis (DPR) residues by ultrafine grinding. The isolated CNF were characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), zeta potential measurement, tensile strength properties, contact angle, as well as oil-proof testing. The CNF were applied as a coating material for cardboard paper sheets made from unbleached kraft DPFS and DPR pulps. The results showed that CNF from DPFS and DPR had close dimensions (4–14 nm in width and several microns in length) but their zeta potential was different (−44.65 eV and −51.46 eV for CNF from DPFS and DPR pulps, respectively), as well as their crystallinity (79.4% and 75.5% for CNF from DPFS and DPR pulps, respectively). CNF films from DPFS had tensile stress and Young's modulus of 113.3 MPa and 3.81 GPa, respectively, while those from DPR had tensile stress and Young's modulus of 71.0 MPa and 2.93 GPa, respectively. Films from DPFS CNF showed lower hydrophilicity than that from DPR, nevertheless excellent oil-proof property was obtained in both kinds of films. Coating of cardboard sheets prepared from unbleached kraft DPFS and DPR pulps with CNF layer of about 7-µm thickness resulted in significant changes in some physical properties of paper sheets, such as decreasing their air permeability, water vapor transmission rate, and water absorption; both kinds of CNF imparted paper sheets good oil-proof properties. CNF coating also imparted paper sheets remarkable wet tensile strength properties. The results showed the feasibility of utilizing date palm wastes in producing CNF films with distinct properties from low-cost unbleached kraft pulp, as well as using these CNF as a multi-functional coating material in papermaking industry.

Effects of Modified Cellulose Fiber and Nanofibril Integration on Basic and Thermo-Mechanical Properties of Paper

This study investigates the influence of fiber modification methods and beating degrees on the properties of paper sheets. Two different methods were used to modify fibers: NaOH + urea and TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) and blended with traditional paper fibers. Subsequently, we evaluated the resulting sheets for their optical, strength, and thermo-mechanical characteristics. Notably, we also scrutinized sheets created exclusively with 100% TEMPO-modified fibers. The addition of modified fibers led to improvements in several strength properties, but it had a noteworthy negative impact on the optical properties of TEMPO-treated fibers compared to the other papers. Furthermore, thermal analysis revealed that the contraction rates of the samples increased considerably up to 40–50 °C for the out-of-plane direction and surpassed 130 °C for the in-plane direction. In general, the inclusion of modified fibers had a significant effect on thermo-mechanical properties. Specifically, TEMPO modification resulted in an increase in the maximum in-plane contraction ratio, shifting it from −0.40% to −0.59%, along with its corresponding temperature. This research underscores the potential of modified fibers to enhance paper properties and contribute to the development of more sustainable paper-based products.

Study on cellulose nanofibers (CNF) distribution behaviors and their roles in improving paper property

Recently, cellulose nanofibers (CNF) have gained significant attention as renewable and high-value nano-biomaterial that has the potential to regulate microstructures and enhance the strength properties of paper products. However, the distribution of CNF in paper sheets may impact the physical properties differently, requiring further understanding. In this study, the effects of different CNF distributions on pore sizes and strength properties in paper sheets were investigated. The hypothesis is that the different distributions of CNF within paper sheets can exhibit different functions in improving the physical properties of paper sheets. Three types of paper sheets containing CNF were respectively prepared by mixing with pulp (CNF (mixture)), distribution on the surface of paper sheets (CNF (surface)) and adding in the middle of paper sheets (CNF (middle)). Results show that CNF can narrow the pore size distribution of paper sheets, particularly in samples with CNF (surface) and CNF (middle) that form dense CNF layers. The highest mechanical strength improvement was observed with mixed CNF. X-ray photoelectron spectroscopy (XPS) analysis revealed that this is due to the strong hydrogen bonding between CNF and pulp fibers, resulting from a large bonding area and effective contact with pulp fibers. This study provides a new perspective on CNF distribution within paper sheets for improving wet web strength properties.

Flocculation of alkyl ketene dimer and calcium carbonate on paper sizing and filling performance

Abstract In order to solve the conflict between precipitated calcium carbonate (PCC) filling and alkyl ketene dimer (AKD) sizing for paper, this study explored two new flocculation methods: AKD and PCC were flocculated separately in the process ((A)(P)F), while the two pre-flocs from AKD and PCC were blended in the process ((AP)F). The result showed that increasing the dosage of the flocculant cationic starch (CS) resulted in a significant growth in the median size of PCC flocs and reduction in the specific surface area, turbidity, the negative charge of Zeta potential, as well as the adsorption capacity of PCC to AKD. Consequently the sizing degree and filler retention rate of the handsheets rose markedly. With 125 mg g−1 of CS, compared with the conventional process, the filler retention rate for (A)(P)F grew up to 86.16%; the Cobb60 values for both (AP)F and (A)(P)F declined, and the contact angle (CA) increased to 120.65° and 127.65° respectively. At the same time, the filler bondability factor (FBF) were increased due to the intensified bonding force between fibers, and resultantly the comparable mechanical properties of papersheets with a high level of filler retention was obtained from (AP)F and (A)(P)F flocculation processes.

Comparison of the internal functionalization and surface modification methods of chemi-mechanical pulp handsheets using nanocellulose, chitosan, and DTPA

The optical and mechanical properties of paper sheets were compared following treatment with biopolymers using two different methods, i.e., internal functionalization and surface modification. Industrial chemi-mechanical pulp was provided, and two groups of paper handsheets were made. The first group of paper sheet samples were prepared with incorporated chitosan in a mixed-in-pulp slurry (at three treatment levels, i.e., 0%, 1%, and 2%), and in the second group, untreated handsheets were spray-coated with either 2% chitosan, 2% nanocellulose, 0.5% DTPA, or a mixed solution (0.5% DTPA + 2% chitosan + 2% nanocellulose). Then, the optical and mechanical properties of the prepared paper sheets were analyzed. The brightness, opacity, and greenness/redness of the samples were measured spectrophotometrically using the CIELab system. Additional properties of the paper, i.e., the water absorption, air permeability, and tear, tensile, and burst resistance, of the treated samples were also measured. The results indicated that the treatments had a considerable effect on the relative mechanical and optical parameters, which resulted in an increase in the mechanical properties, especially when the nano-particles were applied to the mixed-in-slurry process. Inversely, results from the spray-coating method indicated better results for the optical specifications.

Assessment of Mechanical, Water Barrier and Anti-Microbial Properties of Paper Sheets Loaded with Hyperbranched Polyester/ Graphene Oxide Composite and Effect of FlaxSeed-Gel Coatings

Hyperbranched polyester/graphene oxide (HPES/GO) is prepared by in-situ polymerization technique to ensure complete homogeneity of GO in the formed composite. Chemical structure of the composite is studied using FTIR and its thermal stability is investigated by TGA. The prepared composite is used as active filler for cellulosic paper through additions of different ratios during sheets-making. Physical and mechanical properties beside thermal stability of the paper sheets have been examined. The results showed that both density and thermal stability of loaded paper are increased while porosity is decreased significantly with increasing amount of filer. However, the paper sheets demonstrated very low water permeability when loaded with 20% PES/GO. Paper sheets dipped for 1 min. in flaxseed-gel showed improved water vapor permeability compared with uncoated sheets. Moreover, the loaded sheets acquired significant antibacterial activity against different microorganisms. This property is declined upon coating with flax seed gel but still higher than blank sheets.

The Effects of Iron Rust on the Ageing of Woods and Their Derived Pulp Paper.

The accelerated ageing of wood in terms of heating or iron rusting has a potential effect on the physio-mechanical, chemical and biological properties of wood. The effects of accelerated ageing on the mechanical, physical and fungal activity properties of some wood materials (Schinus terebinthifolius, Erythrina humeana, Tectona grandis, Pinus rigida and Juglans nigra) were studied after several cycles of heating and iron rusting. The fungal activity was assayed against the growth of Aspergillus terreus, Aspergillus niger, Fusarium culmorum and Stemphylium solani. In addition, the mechanical and optical properties of paper sheets produced from those wood pulps by means of Kraft cooking were evaluated. The mechanical and chemical properties of the studied wood species were affected significantly (p < 0.05) by the accelerated ageing, compared to control woods. With Fourier transform infrared (FTIR) spectroscopy, we detected an increase in the intensity of the spectra of the functional groups of cellulose in the heated samples, which indicates an increase in cellulose content and decrease in lignin content, compared to other chemical compounds. For pulp properties, woods treated by heating showed a decrease in the pulp yield. The highest significant values of tensile strength were observed in pulp paper produced from untreated, heated and iron-rusted P. rigida wood and they were 69.66, 65.66 and 68.33 N·m/g, respectively; we calculated the tear resistance from pulp paper of untreated P. rigida (8.68 mN·m2/g) and T. grandis (7.83 mN·m2/g) and rusted P. rigida (7.56 mN·m2/g) wood; we obtained the values of the burst strength of the pulp paper of untreated woods of P. rigida (8.19 kPa·m2/g) and T. grandis (7.49 kPa·m2/g), as well as the fold number of the pulp paper of untreated, heated and rusted woods from P. rigida, with values of 195.66, 186.33 and 185.66, respectively. After 14 days from the incubation, no fungal inhibition zones were observed. Accelerated ageing (heated or iron-rusted) produced significant effects on the mechanical and chemical properties of the studied wood species and affected the properties of the produced pulp paper.

Pulp and paper characterization by means of artificial neural networks for effluent solid waste minimization—A case study

Paper mills are among the most polluting industries, responsible for many organic and inorganic compounds emissions. The fibres electro-kinetic features strongly affect the ability to retain fillers since the fillers–fibres interactions are charge induced. The control and the prediction of these parameters would represent a precious aid for process management, allowing the fillers retention enhancement, a lower environmental impact and the paper sheet properties streamlining. The work presented deals with the implementation and training of four artificial neural networks (ANNs) for the prediction of the main electrochemical and physical features of cellulose pulp and paper. First, two ANNs predict the electrochemical parameters. Following, they were applied to predict the paper sheet properties and fillers retention. The neural models implemented showed outstanding prediction performance, with R2 in the order of 0.999 and a low mean error. The results demonstrate how Artificial Neural Networks may be a valuable instrument for paper mill pollutant reduction. However, they suggest a more inclusive investigation for a better fibres behaviour representation.

Preparation of cellulose nanocrystals from deinked waste newspaper and their usage for papermaking

Cellulose nanocrystals (CNC) were successfully prepared from waste newspapers through a simple pretreatment and hydrolysis process. The Fourier transform infrared spectroscopy (FTIR) result for the CNC suggested that no new chemical bonds were formed during the preparation of CNC. X-ray diffraction results indicated that the crystallinities of the deinked and untreated waste newspapers were 66% and 73.8%, respectively. Greater smoothness of the deinked waste newspapers fibers could be clearly observed by scanning electron microscope (SEM), which was attributed to the removal of ink from the chemical treatment. The transmission electron microscopy (TEM) and atomic force microscopy (AFM) results of the CNC revealed a needle-like natural fiber with a length of 300 nm to 600 nm, a diameter of 10 nm to 30 nm, and an aspect ratio in the 10 to 60 range. The obtained CNC particles were found to improve the physical properties of paper sheets, specifically that of the tear, tensile, and burst indices. The maximum increase in the physical properties was achieved with a 5.5% CNC addition.

Using plant extractives as eco-friendly pulp additives: Mechanical and antifungal properties of paper sheets made from linen fibers

In this study, extractives from Pinus rigida heartwood (PRW), Eucalyptus camaldulensis var. obtusa aerial parts (ECL), and Eucalyptus flower buds (ECF) were used as additives in paper sheets produced from the pulp of linen fibers, and their effects on the mechanical and antifungal properties of the paper sheets were studied. The highest tensile and tear indices were 31.5 Nm/g, and 17.3 mNm2/g as pulp treated with PRW (4%), and ECL (1%), respectively. All the pulp additives yielded lower burst index values compared to the control (2.24 KPa.m2/g); the nearest value was 2.23 KPa.m2/g (ECL 4% pulp additive). The brightness percentages (ISO%) ranged from 65.7% to 70.2%, which were lower than the control treatment (70.3%). The paper sheets produced from pulp treated with 2% or 4% PRW, and with 4% ECL suppressed Aspergillus niger growth on the paper disc; pulp treated with 2% or 4% PRW, 4% ECL, and with 2% or 4% ECF completely suppressed A. terreus growth. However, all pulp extract additives did not inhibit the growth of Fusarium culmorum.

Rice straw paper sheets reinforced with bleached or unbleached nanofibers

Abstract Cellulose nanofibers isolated from unbleached pulp are characterized by different surface properties due to presence of lignin at their surface, in addition to lower cost than isolated from bleached pulp. In the current work, the effect of cellulose nanofibers isolated from unbleached neutral sulfite and bleached soda rice straw pulps (so called UBCNF and BCNF) on improving paper sheet properties of unbleached and bleached rice straw pulp (so called UBP and BP) was studied. The effect on mechanical properties (tensile strength, burst strength, and tearing resistance) and physical properties (porosity and water vapor permeability) was studied. Scanning electron microscopy (SEM) was used to assist in explaining the obtained results. The result showed that using BCNF and BP resulted in better improvement in mechanical properties and also more effective in reducing porosity of paper sheets than in case of using UBCNF and UBP. These results indicated stronger bonding between nanofibers and pulps’ fibers in case of using BCNF and BP (surfaces rich in cellulose hydroxyl groups) than in case of UBCNF and UBP (surfaces rich in lignin). Water vapor permeability of paper sheets made from unbleached or bleached pulps did not significantly affect by the addition the nanofibers.

DEVELOPMENT OF WOOD GRINDING 2. EFFECTS OF WOOD MOISTURE ON FIBRE PROPERTIES

"The wood grinding model recently published was based on an energy balance of the active grinding zone, i.e. the limited volumes of wood and grindstone that were heated by the grindstone generated compression and tension strains in the wood surface. Generally speaking, the data obtained in well controlled laboratory grindings complied with the derived model meaning that compression–tension power ratios presented as a function of the specific pulp production resulted in linears. However, the wood moisture contents varying from water-saturated to air-dried wood needed further elaboration for better understanding. Accordingly, the aim of this presentation was to find reasonable explanations for the grinding effects on the wood fibres by considering groundwood pulp and paper sheet properties, for example shives and fines contents, as well as tensile strength and light scattering of the paper sheet. The compression–tension power ratios provided by the model reflect simultaneously both compression and tension strain in wood, and accordingly, the resulting fibre properties would be dependent on both brittle and tough fractures. Evidently, the water contents played a role in this context, both as a stiffener of the water-saturated wood, and as a wood and fibre coolant. "

Reinforcement potential of modified nanofibrillated cellulose in recycled paper production

The influence of nanofibrillated cellulose (NFC) was investigated as a reinforcing agent to improve strength properties of papersheets fabricated from recycled pulp fibers of mixtures of old newspapers, old magazines, and old corrugated cardboards. To determine the effects of the NFC on the mechanical and physical properties of the recycled pulp papers, cellulose nanofibrils (NFC) were isolated from wheat straw, pretreated chemically and enzymatically (NFC-OX), and then added to the bulk suspensions of papermaking pulp slurries at various percentages. The electrokinetic and drainage properties of the pulps and the mechanical and physical properties of the papersheets were analyzed and compared. As expected, the addition of NFC/NFC-OX significantly increased the strength properties of papers. Papers containing 4% of NFC-OX (periodate pretreated) presented higher increases in tensile index (43%) and burst index (59.3%) than other papers. However, a high addition of NFC/NFC-OX increased the water retention, which is undesirable for papermaking. Hence, with optimum selection of NFC/NFC-OX and process conditions, higher mechanical properties could be acquired without increasing drainage rate. Compared to the other pretreated NFC/NFC-OX types, sodium-periodate-oxidized NFC-OX samples significantly increased the mechanical properties of the papers fabricated from the recycled pulps.

MICRO- AND NANOPARTICLES FROM HEMP SHIVES AND HEMP CELLULOSE IN PAPERMAKING

Nano- and microparticles were produced from hemp shives and hemp cellulose obtained thereof, using the thermocatalytic mechanical destruction method. The partially destructed material, at concentrations of 8-9%, was dispersed in water medium in a ball mill or ground without the presence of water in a ball mill (~15 h). In the first case, a gel-like dispersion, which contained nanoparticles and microparticles, was obtained. In the second case, microparticle powder (from hemp shives) was obtained. The obtained materials were used as fillers and coatings in paper sheets. The air resistance and mechanical properties of paper sheets were investigated. It has been established that the nano/microparticle fillers improve the mechanical properties and air resistance of paper sheets. The properties of paper are improved also by coatings made from nanoparticle gels on both sides of paper sheets. Therefore, the nano/microparticle fillers and coatings obtained from hemp shives and hemp cellulose can be used in papermaking, improving the properties of paper sheets.

Preparation of an amphoteric lignin copolymer and its value in the papermaking industry

Lignin biomass is an important renewable woody material that can be converted into high value-added products through physical and chemical reactions, such as paper strength additives. In this study, a cationic methacryloyloxyethyl trimethylammonium chloride monomer (DMC) and anionic acrylic monomer (AA) were grafted onto softwood kraft lignin through free radical polymerization to prepare an amphoteric lignin copolymer. Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H NMR), elemental analysis, and charge density analysis methods confirmed that the anionic and cationic monomers were successfully grafted onto the lignin. The grafting ratios of AA and DMC monomer in the lignin-DMC-AA copolymer were 62.4% and 51.3%, respectively. The application of lignin-DMC-AA copolymer as a paper additive for enhancing the physical properties of paper sheets was studied in the papermaking industry. The results indicated that the copolymer had a maximum increase in physical strength at around 2 wt% lignin-DMC-AA. The amount absorbed on the fibers was 18.5 mg/g, and the retention of the lignin-DMC-AA copolymer was over 90%.

Study of the Effect of Titanium Dioxide Hydrosol on the Photocatalytic and Mechanical Properties of Paper Sheets.

Different amounts of a stable aqueous TiO2 hydrosol were used to fabricate paper sheets having photocatalytic activity. The TiO2 hydrosol was prepared in aqueous medium using titanium butoxide as precursor and acetic acid as catalyst for the hydrolysis of titanium butoxide. An aging process at room temperature and atmospheric pressure was finally applied to obtain crystalline anatase TiO2 hydrosol. The effects of different TiO2 hydrosol loadings on the mechanical strength and barrier properties of modified paper sheets were investigated in detail. The photocatalytic behavior of TiO2-modified paper sheets was investigated as well using methylene blue (MB) as target pollutant.

Impact of Three Natural Oily Extracts as Pulp Additives on the Mechanical, Optical, and Antifungal Properties of Paper Sheets Made from Eucalyptus camaldulensis and Meryta sinclairii Wood Branches

In the pulp and paper industry, several studies have been done to improve and enhance the properties of the mechanical, optical, and antimicrobial activities of pulp produced with different additives. In the present study, pulp of wood branches (WBs) from Eucalyptus camaldulensis Dehnh. and Meryta sinclairii (Hook.f.) Seem. was treated with n-hexane oily extracts (HeOE) from Melia azedarach L. fruits, Magnolia grandiflora L. leaves, and Sinapis alba L. seeds as additives at concentrations of 1%, 3%, and 5% based on oven-dry pulp weight. Measured mechanical properties were higher in paper sheets made from E. camaldulensis than M. sinclairii WB pulp. The highest tensile index values were observed with E. camaldulensis WB pulp treated with 5% HeOEs of S. alba (33.90 N·m/g) and M. grandiflora (33.76 N·m/g) compared to control (32.10 N·m/g); the highest tear index with 5% HeOE of S. alba (4.11 mN·m2/g) compared to control (3.32 mN·m2/g); and the highest burst index with 5% HeOE of S. alba (4.11 kPa·m2/g) compared to control (3.08 kPa·m2/g). The highest double-fold number value (9) was observed with E. camaldulensis WB pulp treated with 5% HeOEs of S. alba, M. azedarach, and M. grandiflora but with no significant difference compared to control treatment (8.33) or other HeOE treatments with E. camaldulensis WB pulp. Scanning electron microscope (SEM) examination showed clear inhibition of the growth of Aspergillus terreus with WB pulp paper discs of E. camaldulensis and M. sinclairii treated with HeOEs of M. azedarach, S. alba, and M. grandiflora at 3% and 5% compared to control treatment, while HeOEs at 5% concentration showed no growth of A. niger and A. terreus. The present findings establish that the HeOEs from M. azedarach, S. alba, and M. grandiflora at 3% and 5% are novel natural products that can be used as alternatives to improve the properties and antifungal activity of WB pulp produced from E. camaldulensis and M. sinclairii.

Improving moisture barrier properties of paper sheets by cellulose stearoyl ester-based coatings

As commonly-used packaging material, paper has very poor moisture barrier properties, which are essential for maintaining physical and mechanical performance of paper as well as the shelf life of the packed goods. Herein, solutions of the synthesized cellulose stearoyl ester (CSE) compound were coated onto the calendered paper sheets by bar coater with the coating grammage ranging from 0.5–23.6 g m−2. When the coating grammage was 5.2 g m−2, the paper surface was totally covered by the CSE film with very low surface roughness (2.327 nm). The resulting CSE-coated papers from this coating grammage showed decreased tensile index and increased elongation at break, indicating the flexibility of the coated papers. Furthermore, the coated paper sheets were hydrophobic and displayed competitive water vapor barrier properties with the barrier ratio up to 90 %. Thereby, the designed CSE-coated paper sheets are promising for moisture barrier packaging application.