Influence of tensile straining and fibril angle on the stiffness and strength of previously dried kraft pulp fibers

TAPPI Journal ◽  
2018 ◽  
Vol 17 (07) ◽  
pp. 383-392 ◽  
Author(s):  
John Long ◽  
Warren Batchelor
Keyword(s):  
Tensile Modulus ◽  
Middle Layer ◽  
Theoretical Models ◽  
Maximum Load ◽  
Radiata Pine ◽  
Wood Fibers ◽  
Pulp Fibers ◽  
Pulp Processing ◽  
S2 Layer ◽  
Fibril Angle

It has long been known that in individual wood fibers, the tensile mechanical properties are heavily determined by the nature of the cellulose chains in the fibers. Both elastic tensile modulus and strength are directly related to the fibril angle, which is the steepness with which the cellulose chains wind their way around the fiber in the secondary wall of the middle layer, named the S2 layer. Classic work from the 1970s measured modulus and strength in wood fibers as a function of the fibril angle and compared the results with theoretical models. The measurements were hampered by the presence of defects in the fibers, some which occurred naturally and others which resulted from pulp processing. In this study, we performed more accurate measurements of strength and modulus in single fibers of radiata pine by loading the fibers in cycles, gradually pulling some of the defects out of the fibers in an attempt to obtain defect-free values of modulus and strength. We then plotted these properties against measured fibril angle and compared our results with theoretical models. The results show that even when the fiber had reached maximum load before fracture, at a given value of fibril angle, it still had a measured modulus that is around half the theoretically expected value. The results suggest that the load required to fully remove defects from the fibers may be larger than the fibers can bear before fracturing.

Effect of particle size, fiber content, and surface treatment on the mechanical properties of maple-reinforced LLDPE produced by rotational molding

2020 ◽  
pp. 096739112091660
Author(s):  
Fatima Ezzahra Hanana ◽  
Denis Rodrigue
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Surface Treatment ◽  
Tensile Modulus ◽  
Complete Characterization ◽  
Fiber Content ◽  
Wood Fibers ◽  
Interface Quality ◽  
Effect Of Particle Size ◽  
The Impact

In this work, composites based on linear low-density polyethylene and maple wood fibers with and without surface treatment with maleated polyethylene (MAPE) were prepared by dry blending, followed by rotomolding to study the effect of particle size, fiber content, and surface treatment. From the samples produced, a complete characterization of the morphological and mechanical properties was performed. The results obtained showed that MAPE surface treatment improved the fiber–matrix interface quality, which improved the homogeneity, the thermal stability, and the mechanical properties of the composites. The results showed that the effect of particle size was significant as the tensile modulus increased by 7%, 40%, and 73% for 125–250, 250–355, and 355–500 µm at 30 wt% of maple fibers. The tensile strength also increased by 114% at the same fiber loading (30 wt%) when the particle size increased from 125–250 µm to 355–500 μm. Finally, the impact strength with 355–500 µm particles was 52% higher than for 125–250 µm particles at 30 wt%

scholarly journals Comparative studies on wood structure and microtensile properties between compression and opposite wood fibers of Chinese fir plantation

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Zhu Li ◽  
Tianyi Zhan ◽  
Michaela Eder ◽  
Jiali Jiang ◽  
Jianxiong Lyu ◽  
...  
Keyword(s):  
Cellulose Microfibril ◽  
Microfibril Angle ◽  
Tensile Modulus ◽  
Scientific Basis ◽  
Ultimate Tensile Stress ◽  
Chinese Fir ◽  
Cellulose Content ◽  
Wood Fibers ◽  
Opposite Wood ◽  
Chinese Fir Plantation

AbstractThe microtensile properties of mechanically isolated compression wood (CW) and opposite wood (OW) tracheids of Chinese fir (Cunninghamia lanceolata) were investigated and discussed with respect to their structure. Major differences in the tensile modulus and ultimate tensile stress were found between CW and OW fibers. Compared to OW, CW showed a larger cellulose microfibril angle, less cellulose content and probably more pits, resulting in lower tensile properties. These findings contribute to a further understanding of the structural–mechanical relationships of Chinese fir wood at the cell and cell wall level, and provide a scientific basis for better utilization of plantation softwood.

scholarly journals Preparation and Performance of Radiata-Pine-Derived Polyvinyl Alcohol/Carbon Quantum Dots Fluorescent Films

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 67 ◽  
Author(s):  
Li Xu ◽  
Yushu Zhang ◽  
Haiqing Pan ◽  
Nan Xu ◽  
Changtong Mei ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Water Resistance ◽  
Cellulose Nanofibers ◽  
Tensile Modulus ◽  
Radiata Pine ◽  
Carbon Quantum Dots ◽  
Nanocomposite Films ◽  
Excitation Wavelength ◽  
Nano Materials ◽  
Nano Composite

In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials.

Selective enzyme impregnation of chips to reduce specific refining energy in alkaline peroxide mechanical pulping

Holzforschung ◽  
2009 ◽  
Vol 63 (4) ◽  
Author(s):  
Peter W. Hart ◽  
Darrell M. Waite ◽  
Luc Thibault ◽  
John Tomashek ◽  
Marie-Eve Rousseau ◽  
...  
Keyword(s):  
High Spatial Resolution ◽  
Enzyme Hydrolysis ◽  
Chemical Pretreatment ◽  
Alkaline Peroxide ◽  
Fiber Wall ◽  
Transmission Electron ◽  
Eucalyptus Wood ◽  
Pulp Processing ◽  
Two Stages ◽  
S2 Layer

Abstract Eucalyptus wood chips were impregnated with various blends of fiber modifying enzymes prior to preconditioning refiner chemical-alkaline peroxide mechanical pulp processing. The process includes chemical pretreatment and two stages of refining. The energy consumption was compared at the same Canadian standard freeness level of 350 ml. Some enzyme treatments were found to reduce specific refining energy (SRE) by at least 24%. The enzyme hydrolysis within the cell wall was observed by transmission electron microscopy of impregnated chips with high spatial resolution. The enzyme blends that successfully reduced SRE requirements were found to selectively loosen the bonds between the S1 and S2 layers of the fiber wall. Enzymes which selectively attached the S2 layer did not impart any SRE reduction. All experiments for impregnation and pulp processing were conducted at the Andritz Pilot Plant in Springfield, OH.

scholarly journals Full-field hygro-expansion characterization of single softwood and hardwood pulp fibers

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
N. H. Vonk ◽  
M. G. D. Geers ◽  
J. P. M. Hoefnagels
Keyword(s):  
Strain Tensor ◽  
Surface Strain ◽  
Pulp Fibers ◽  
Full Field ◽  
Long Duration ◽  
Large Spread ◽  
Surface Topographies ◽  
Hardwood Pulp ◽  
Fibril Angle

AbstractThe dimensional stability of paper products is a well-known problem, affecting multiple engineering applications. The macroscopic response of paper to moisture variations is governed by complex mechanisms originating in the material at all length-scales down to the fiber-level. Therefore, a recently-developed method, based on Global Digital Height Correlation of surface topographies is here exploited to measure the full-field hygro-expansion of single fibers, i. e. a surface strain tensor map over the full field of view is obtained as function of time. From the strain field, the longitudinal and transverse hygro-expansion and principle strains can be calculated. Long- and intermediate-duration dynamic tests are conducted on softwood and hardwood fibers. A large spread in the softwood fiber’s transverse and longitudinal hygro-expansion coefficient ratio was found, while hardwood fibers behave more consistently. Computing the principle strain ratios reduces this spread, as it takes into account the variations of the deformation direction, which is directly affected by the micro-fibril angle (MFA). Furthermore, long-duration tests allow identification of the half-times at which the fibers equilibrate. Finally, the determined major strain angles for all fibers are consistent with the MFA ranges reported in the literature.

Effect of aluminum nitride concentration on different physical properties of low density polyethylene based nanocomposites

2017 ◽  
Vol 37 (8) ◽  
pp. 765-775 ◽  
Author(s):  
Omer Bin Sohail ◽  
Osamah A. Bin-Dahman ◽  
Mostafizur Rahaman ◽  
Mamdouh A. Al-Harthi
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Constant ◽  
Aluminum Nitride ◽  
Tensile Modulus ◽  
Theoretical Models ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Scanning Calorimetry ◽  
Composite Systems ◽  
Present Composite

Abstract In this study, blends of low-density polyethylene (LDPE)/aluminum nitride (AlN) ceramic nanocomposites have been prepared through melt blending technique. Increased loading of AIN leads to reduction in tensile properties but improvement in rheological property (storage modulus). The rheological behavior tends to become unique at higher frequencies (≥10 rad/s). Differential scanning calorimetry (DSC) results show that the total crystallinity has decreased with the increase in AlN loading in the composites. It is seen that there is an improvement in electrical conductivity, dielectric constant, and flammability properties with the addition of AlN in the nanocomposites. The experimental data of tensile modulus, electrical conductivity, and dielectric constant have been fitted with some available theoretical models to check the models’ applicability for the present composite systems. Results show that only Nicolais-Nicodemo model, McCullough model, and Rahaman-Khastgir model are applicable for predicting the tensile modulus, electrical conductivity, and dielectric constant of the composites, respectively.

scholarly journals Injection Molding of Highly Filled Polypropylene-based Biocomposites. Buckwheat Husk and Wood Flour Filler: A Comparison of Agricultural and Wood Industry Waste Utilization

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1881 ◽  
Author(s):  
Jacek Andrzejewski ◽  
Mateusz Barczewski ◽  
Marek Szostak
Keyword(s):  
Injection Molding ◽  
Wood Flour ◽  
Wood Fiber ◽  
Flow Characteristics ◽  
Tensile Modulus ◽  
Mechanical Tests ◽  
Waste Utilization ◽  
Wood Fibers ◽  
Adhesion Promoter ◽  
Buckwheat Husk

The study presents a comparative analysis for two types of polymer fillers used during the processing of polypropylene by the injection molding technique. The aim of the study was to assess the usefulness of buckwheat husk waste as an alternative to the widely used wood fiber fillers. For this purpose, we prepared composite samples containing 10, 30 and 50 wt % of the filler, which were subjected to mechanical tests, thermal analysis, and structural observations in order to evaluate and compare their properties. Additionally, we evaluated the effectiveness of the composite system’s compatibility by using maleic anhydride grafted polypropylene (PP-g-MA). The results of mechanical tests confirmed a more effective reinforcement mechanism for wood fibers; however, with the addition of PP-g-MA compatibilizer, these differences were significantly reduced: we observed a 14% drop for tensile modulus and 5% for strength. This suggests high susceptibility to this type of adhesion promoter, also confirmed by SEM observations. The paper also discusses rheological measurements conducted on a rotational rheometer, which allowed to confirm more favorable flow characteristics for composites based on buckwheat husks.

Wood Pulp Fibers Grafted with Polyacrylamide through Atom Transfer Radical Polymerization

2011 ◽  
Vol 396-398 ◽  
pp. 1458-1461 ◽  
Author(s):  
Xiu Mei Zhang ◽  
Jian Feng Ji ◽  
Yan Jun Tang ◽  
Yu Zhao
Keyword(s):  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Monomer Concentration ◽  
Wood Pulp ◽  
Hydroxyl Groups ◽  
Atom Transfer ◽  
Wood Fibers ◽  
Pulp Fibers ◽  
Grafting Reaction ◽  
Ft Ir

Bleached wood pulp fibers grafted with polyacrylamide (PAM) was synthesized through surface-initiated atom transfer radical polymerization (SI-ATRP) to be applied in papermaking. The ATRP macroinitiator was prepared by esterification of hydroxyl groups of wood fibers with α-bromoisobutyryl bromide (α-BIBB). The bromine atoms on the surface of the macroinitiator were characterized and calculated by FT-IR, EDXS and TGA techniques. The ATRP grafting reaction conditions of fiber-PMA were discussed and determined. To optimize the polymerization in the CuBr/PMDETA catalytic system, several influencing factors on grafting yield were investigated, including solvent, reaction temperature, monomer concentration and sacrificial initiator. The PAM grafted fibers were characterized by FT-IR and TGA analyses.

scholarly journals The effects of poplar bark and wood content on the mechanical properties of wood-polypropylene composites

BioResources ◽  
2011 ◽  
Vol 6 (4) ◽  
pp. 5180-5192
Author(s):  
Vahidreza Safdari ◽  
Hamed Khodadadi ◽  
Seyyed Khalil Hosseinihashemi ◽  
Esmaiel Ganjian
Keyword(s):  
Mechanical Strength ◽  
Fiber Strength ◽  
Wood Flour ◽  
Flexural Modulus ◽  
Tensile Modulus ◽  
Raw Material ◽  
Wood Fibers ◽  
Polypropylene Composites ◽  
Twin Screw ◽  
Length Width

Bark, as a residue from trees, is mostly used for thermal energy production, but a better utilization of this resource was considered as an alternative raw material for wood-plastic composites (WPCs). The influence of bark, wood, and blending of bark and wood flour content of the poplar tree on the mechanical characteristics of WPCs were investigated. Wood and bark flours with 2% maleic anhydride-grafted polypropylene (MAPP) and polypropylene were compounded into pellets using a counter-rotating twin-screw extruder, and test specimens were prepared by injection molding. The results showed that both bark fiber and wood flour increased mechanical strength (flexural strength (MOR), flexural modulus (MOE), tensile modulus, and tensile strength) significantly (P<0.05). Composites made with bark flour exhibited lower mechanical strength compared to those made with wood flour and wood flour/bark flour. Differences in chemical composition between bark and wood, fines, low aspect ratio (length/width) of bark flour, delamination between fines and matrix, and the lower intrinsic fiber strength of bark fibers compared to wood fibers are good explanations for this demarcation. The notched impact strength of all reinforced composites was significantly lower than neat polypropylene (P < 0.05).

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