Improvement of the physical properties of paper sheet-lignophenol composites prepared using a facile impregnation technique
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Lignophenol was separated from bamboo (Sinocalamus affinis) using a phase separation system. Different concentrations of a lignophenol-acetone solution were used to impregnate hardwood pulp fiber sheets (80 g/m2). The results showed that the tightness, tensile index, tear index, and burst index properties of sheets impregnated with a lignophenol acetone solution (80 g/L) increased 5.66%, 160.08%, 93.66%, and 140%, respectively, compared with sheets prepared without lignophenol. The lignophenol-hardwood pulp fiber composites were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and total reflectance Fourier transform infrared spectroscopy. The results indicated that lignophenol uniformly adhered to the pulp fibers but no chemical bonding occurred. Additionally, both virgin and recycled softwood pulp fiber sheets (80 g/m2) were tested using the same method. Although the strength of all composites increased after impregnation, the most obvious improvement was observed in the hardwood pulp-based composite. This simple method improved the physical strength and hydrophobicity of the composite sheets.Keywords:
Softwood
Tear resistance
In this study, the effect of molding condition on the tensile properties for plain woven hemp fiber reinforced green composite was examined. The tensile properties of the composite were compared with those of the plain woven jute fiber composite fabricated by the same process. Emulsion type biodegradable resin or polypropylene sheet was used as matrix. The composites were processed by the compression molding where the molding temperature and its heating time were changed from 160 to 190°C and from 15 to 25 min, respectively. The following results were obtained from the experiment. The tensile property of hemp fiber reinforced polypropylene is improved in comparison with polypropylene bulk. The strength of composite is about 2.6 times that of the resin bulk specimen. Hemp fiber is more effective than jute fiber as reinforcement for green composite from the viewpoint of strength. The molding temperature and time are suitable below 180°C and 20 min for hemp fiber reinforced green composite. Hemp fiber green composite has a tendency to decrease its tensile strength when fiber content is over 50 wt%.
Polypropylene
Molding (decorative)
Compression molding
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Softwood
Newsprint
Synthetic fiber
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In order to determine the quantitative relationship between sheet strength and lignin coverage at the fiber surface, CTMP was blended with softwood bleached kraft pulp (BKP), refined softwood BKP, and hardwood BKP. The morphology of the fibers, fibers properties, fiber surface components and relative bonded area of sheets were investigated. Multi-linear regression equations of tensile strength index and internal bond strength were established. The results indicated that unbleached aspen CTMP fiber surfaces were covered by granules of lignin, and BKP fiber surfaces were predominated covered by microfibrils. Fiber properties have a significant impact on tensile strength index. RBA had a greater impact on IBS than lignin coverage. For the pulp samples tested, a 1% increase in lignin coverage at fiber surfaces would lead to a 0.48N·m/g decrease in tensile strength index and 5.32×10-3 J/m2 decrease in internal bond strength.
Softwood
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The applications of NCC/CS in papermaking were explored in this paper. The results were as follows:(1)adding a single NCC or CS has some strengthening effect on tensile strength, tear strength and bursting strength of paper;(2)Comparing to the adding mode which was CS and NCC fixed before adding to paper, the results of paper strength were better when CS was added into the pulp followed by NCC;(3)When the adding dosage of CS and NCC were 1% and 0.6%, For the hardwood paper, relatively to the original paper, the dry tensile index, tear index and the burst index were increased by 76.3%, 50.6%, 63.4%, and the folding index was sevenfold compared to the original paper. For the mixing paper consisting of 40% softwood pulp and 60% hardwood pulp, relatively to the original paper, the dry tensile index, tear index and folding index were increased by45.7%, 25.2%, 99.4%.
Papermaking
Folding endurance
Softwood
Tear resistance
Cellulose fiber
Cationic polymerization
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SiC short fiber(as-received and treated with couple agent) strengthened polytetrafluoroethylene(PTFE) composites were prepared through mixing and cold pressing.The mechanical,friction and wear properties of the composites were tested.The effects of the surface treatment on the performance of the composites were investigated.The fracture surfaces by tensile stress were observed by using a scanning electron microscope(SEM).The strengthen mechanism for the composites was proposed.The results indicated that the tensile strength,impact strength,and friction and wear properties of the composites with surface treated SiC fiber are higher than those with as-received SiC fiber.SEM observation of fracture surfaces showed that poor bonding interface with gaps between untreated SiC fiber and the PTFE matrix is responsible for the lower performances of the corresponding composites.The couple agent surface treated SiC fiber has a strong adhesion with PTFE so that less SiC fiber were pull out during tensile process.
Polytetrafluoroethylene
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Acoustic emission (AE) that occurred during the tearing of handsheets made from softwood or hardwood kraft pulp beaten to various degrees was measured and analysed to investigate the relationship between tear strength and the micro failures that occurred. Maximum amplitude distribution of the AEs correlated with the frequency of fibre failure and failures of strong and weak fibre bonds with an increase in beating degree. As a result, the increase in tear strength by lightly beating both pulps corresponded to increases in fibre failure and failure of strong fibre bonds. The decrease in tear strength with further beating of the softwood pulp corresponded to decreases in fibre failure and failure of strong fibre bonds. The marginal increase in tear strength by further beating the hardwood pulp corresponded to an increase in fibre failure and decrease in failure of strong fibre bonds.
Tearing
Softwood
Tear resistance
Bonding strength
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The surface of Al2O3 fiber was treated by titanate coupling agent. The mechanical and tribological properties of polytetrafluoroethylene( PTFE) reinforced by Al2O3 fiber were studied. The tensile fracture surfaces of the composite were observed by scanning electron microscopy( SEM). The results showed that the tensile strength,impact strength,and friction and wear properties of Al2O3 fiber / PTFE composite treated with coupling agent were increased. SEM observation of fracture surfaces showed that the interface bonding performance of PTFE and Al2O3 fiber treated with coupling agent was better.
Polytetrafluoroethylene
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Reinforcing highly refined pressure groundwood with softwood kraft pulp increased tensile stiffness. Tensile rupture strain increased, thus indicating that tensile strength index increases slightly more than tensile stiffness index. There was considerable nonlinearity in the tensile strength index of reinforced groundwood paper as a function of the proportion of reinforcement pulp with small amounts of kraft pulp producing no increase in strength. Adding softwood kraft pulp to a hardwood kraft pulp had little effect on stiffness and strength. Addition of softwood kraft reinforcement pulp had a much greater effect on the fracture energy of paper than on tensile strength. Assuming that the fracture energy (or toughness) together with flaw size distribution determines the greatest load a paper web can carry, it may be feasible to evaluate softwood reinforcement pulps based on the fracture energy. The fracture energy of paper appears to be a linear function of the proportion of reinforcement pulp, suggesting that reinforcement pulps might be evaluated from pure kraft pulp handsheets. Application: softwood kraft fiber reinforcement is effective in papermaking and converting operations where the fracture energy is a crucial material property. The effect of reinforcement on other mechanical properties seems much more moderate.
Softwood
Papermaking
Tear resistance
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Cure characteristics and mechanical properties of short nylon fiber reinforced natural rubber composites have been studied. Minimum torque, (maximum-minimum) torque and cure rate increased with fiber concentration. Scorch time and cure time decreased by the addition of fibers. Properties such as tensile strength, tear strength, elongation at break, heat build up and abrasion resistance were studied both in specimens with both longitudinal and transverse orientation of fibers. Tensile strength showed a marked minimum at 10 phr of fiber loading beyond which it increased with fiber content. Tear strength, abrasion resistance and heat build up increased with the addition of fibers, whereas elongation at break decreased with fiber content. Ageing resistance of the composites was better than that of the gum compound.
Tear resistance
Elongation
Abrasion (mechanical)
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Research has been undertaken with the aim of displacing the tensile-tear relationship towards higher strength values. Three commercial pulps were refined in an Escher-Wyss conical refiner. A softwood sulphate pulp was refined to three different levels of dewatering resistance, while a southern pine pulp and an abaca pulp were refined separately to a dewatering resistance of 17SR. The amount of fines in these two pulps was reduced by fractionation on a bow screen. Two-layer laboratory sheet were produced in a multilayer handsheet former and compared with single-layer sheets made from an homogeneous mixture of the two pulps, either softwood plus southern pine or softwood plus abaca. Analysis revealed that when increasing the degree of refining for the softwood pulp, the tensile index for the stratified sheets was increased and reached a constant level at 27.5 SR. For the mixed sheets, the tensile index increased further with increased refining. While the tear index remained at a fairly constant level for the stratified sheets, it decreased for the mixed sheets with increased degree of refining. No effect of the stratification was observed for the sheets consisting of softwood and southern pine. It has been shown that by placing a reinforcement pulp of considerably higher tearing resistance potential than the bulk pulp in a separate layer instead of homogeneously mixing the pulps, the tensile index of the sheet can be increased by increased refining of the bulk pulp with maintained tear index
Softwood
Tear resistance
Tearing
Dewatering
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