• Elastomers and Composites
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• v.46 no.3
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• pp.186-194
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• 2011

Natural fiber/natural rubber composites were fabricated by uniformly compounding natural rubber and cellulose- based natural fiber kenaf and then by compression molding. The effect of kenaf fiber content on their vulcanization behavior, hardness, tensile properties, tear strength and static and dynamic properties was investigated. The contents of kenaf fiber in the composites were 0, 5, 10, 15, and 20 phr, compared to natural rubber and additives. The result indicated that various properties of natural rubber depended on the kenaf fiber content. With increasing kenaf fiber content, the torque for vulcanization of natural rubber was increased whereas the vulcanization time was reduced as well. The hardness, tensile modulus and tear strength of kenaf/natural rubber composites were gradually decreased with the fiber content whereas the tensile strength and elongation at break were decreased. Also, with increasing the kenaf fiber content the dynamic property of natural rubber was changed more greatly than the static property. The loss factor, which is closely related with the damping or absorption of the energy given to natural rubber, was proportionally increased with the fiber content.

• Elastomers and Composites
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• v.33 no.4
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• pp.281-289
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• 1998

Tensile properties including Young's modulus and tear strength were measured for four different rubber compounds; natural rubber(NR), styrene-butadiene copolymer(SBR), ethylene-propylene diene monomer (EPDM), and brominated isobutylene-p-methyl-styrene copolymer(BIMS) as a function of temperature and degree of cure. To see the effect of over cure, a measurement was made of the tensile strength and swelling behavior of the over-cured rubber compounds. Young's modulus, E, was found to have linear dependency on the degree of cure for all rubber compounds. EPDM and BIMS showed the highest and lowest slopes, respectively. The slope of NR and SBR lay between EPDM and BIMS. Tear strength, Gc, decreased in the order of NR>BIMS>SBR>EPDM. As the cure time was extended the degree of cure of NR and SBR decreased, while that of BIMS increased. EPDM showed little change in the degree of cure.

• Journal of Korean Orthopaedic Sports Medicine
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• v.5 no.1
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• pp.50-57
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• 2006

Purpose: The purpose of this study was to evaluate the tendon healing of arthroscopic repair in full-thickness supraspinatus tears. We evaluate the effectiveness of the arthroscopic repair of full-thickness supraspinatus tears by assessing functional improvement. Materials and Methods: Thirty consecutive full-thickness supraspinatus tears were repaired arthroscopically in 19 patients with a one row of anchor and 11 patients with two rows of anchors. Patients ranged in age from 51 to 79 years (average 63 years). Average follow-up was 16 month (range, 12 to 28 months). To evaluate the effectiveness of the arthroscopic repair of full-thickness supraspinatus tears by assessing functional improvement, we calculate the Constant, ASES, UCLA scores. The 30 patients had either an MR Arthrogram (25 cases) or an MRI (5 cases), performed between 5 months and 20 months (mean 10 months) after surgery. Results: The cuff was healed in 21/30 cases (70%) and partially torn in 3 cases (10%) after the arthroscopic repair of full-thickness supraspinatus tear. Although the supraspinatus tendon was totally torn to the tuberosity in 6 cases(20%) after the arthroscopic repair, the size of the tear was smaller than the initial in 5 cases. The Constant score improved from an average of $55.7{\pm}7.1$ points preoperatively to $77.7{\pm}9.7$ points at the last follow-up (p<0.001), and the average ASES score improved from $39.2{\pm}7.4\;to\;72.4{\pm}12.6$ (p<0.001), and the average UCLA score improved from $17.9{\pm}2.2\;to\;26.8{\pm}5.0$ (p<0.001). Strength of elevation was significantly better $(7.1kgs{\pm}2.4)$ in the shoulders with a healed tendon that in those with an total or partial re-tear tendon $(4.5kgs{\pm}1.0)$ (p<0.05). Factors adversely affecting tendon healing were increasing age, Only 41.7% of the repairs completely healed in patients over 65 years (p<0.05). Conclusion: Arthroscopic repair of isolated full-thickness tear of the supraspinatus leads to completely healing in 70% of the cases. Total or partial re-tear of the repaired rotator cuff is associated with a decreased strength. Older patients had significantly lower healing rates.

• Elastomers and Composites
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• v.34 no.1
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• pp.31-44
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• 1999

Interfacial adhesive strength between the fully-crosslinked and partially-crosslinked rubber layers were Investigated at the temperature range of $30{\sim}120^{\circ}C$ for four different rubbers(NR, SBR, EPDM, BIMS). The surfaces of interfacial failure were also investigated using a scanning electron microscopy(SEM). The physical interlinking played a major role in the adhesive strength between the fully-crosslinked rubber layers. When a partially-crosslinked rubber layer was bonded to the fully-crosslinked one, the chemical as well as the physical interlinking affected the adhesive strength. NR showed a "interfacial knotty tearing" pattern, while EPDM showed a typical "cross-hatched" one when the adhesive strength approached to the cohesive tear strength of each material.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.04a
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• pp.39-46
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• 2000

In pulp and papermaking process, enzymatic treatment of pulp fibres has been a topic of increasing interest in last decade. Lots of patents, papers and research reports were published on the application of enzymes in the fields of enzymatic bleaching, deinking, slime control, pitch control, waste water treatment and fibre modification. Cellulase and hemicellulase are the principal enzymes used for the modification of fibre property. This study was carried out for determinating the behaviors of enzyme to pulp fibres. A commercial enzyme, Denimax BT which is consisted with cellulase and hemicellulase, was treated to the kraft pulp produced from domestic hardwood mixtures. Results were mainly concentrated on the behaviors of freeness, drainability and fines content of fibres, and physical properties of paper with enzyme treatment. The freeness levels and dewatering ability were developed, and the fines contents were decreased. The creation of fines were controlled by the method of pre-enzyme treatment prior to fibre beating. The mechanical strength of paper, like tensile, burst, tear strength and folding endurance, were remarkably improved by the pre-enzyme treatment.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.11a
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• pp.201-206
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• 2006

Embossing treated fruit bagging paper was prepared with newly designed embossing roll and mechanical properties of fruit bagging paper were evaluated. The embossing technology was developed. First of all, embossing roll was designed in Ginyong Embo(Co) for the embossing process of fruiting bag. The embossing treated fruit bagging paper was manufactured in Agro(Co) at plant scale. The mechanical properties of embossing paper was investigated and operation efficiency of bagging was tested at field. The properties of embossed paper was quit satisfied for fruiting bag for cultivation of apple and pears.

• Steel and Composite Structures
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• v.9 no.2
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• pp.173-189
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• 2009

This paper presents a study on the behavior and design of bolted stainless steel plates under in-plane tension. Using an experimentally validated finite element (FE) program strength of stainless steel bolted plates under tension is examined with an emphasis on plate bearing mode of failure. A numerical parametric study was carried out which includes examining the behavior of stainless steel plate models with various proportions, bolt locations and in two different material grades. The models were designed to fail particularly in bolt tear-out and material piling-up modes. In the numerical simulation of the models, non-linear stress-strain material behavior of stainless steel was considered by using expressions which represent the full range of strains up to the ultimate tensile strain. Using the results of the parametric study, the effect of variations in bolt positions, such as end and edge distance and bolt pitch distance on bearing resistance of stainless steel bolted plates under in-plane tension has been investigated. Finally, the results obtained are critically examined using design estimations of the currently available international design guidance.

• Textile Coloration and Finishing
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• v.2 no.1
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• pp.14-20
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• 1990

The cotton fabrics were treated with formaldehyde in the presence of zinc nitrate catalyst and urea. The effects of HCHO concentration, urea concentration, catalyst ratio, cure time and cure temperature on the physical properties of fabrics were studied. Cotton fabric finished with HCHO and urea had the lower tensile strength and tear strength than untreated one. These strength losses resulted from tighter oxymethylene crosslinks. The enhanced wrinkle recovery for fabric treated with formaldehyde in the presence of urea was indicative of the formation of urea-formaldehyde polymer. These experimental conditions were set up according to table of orthogonal arrays.

• Rubber Technology
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• v.5 no.2
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• pp.94-103
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• 2004

The present work describes modification of dual phase filler by electron beam irradiation in presence of multifunctional acrylates like trimethylol propane triacrylate (TMPTA) or silane coupling agent like bis (3-triethoxysilylpropyltetrasulphide) and in-fluence of the modified fillers on the physical properties of styrene-butadiene rubber (SBR) vulcanizates. Modulus at 300 % elongation increases whereas the tensile strength decreases with increase in radiation dose for the dual phase filler loaded styrene-butadiene rubber vulcanizates (SBR). However, modulus and tensile strength significantly increase, which is more, pronounced at higher filler loadings for TMPTA modified dual phase filler loaded SBR. These changes in properties are explained by the equilibrium swelling data and Kraus plot interpreting the polymer-filler interaction. Electron beam modification of the filler results in a reduction of tan ${\delta}$ at $70^{\circ}C$, a parameter for rolling resistance and increase in tan ${\delta}$ at $0^{\circ}C$, a parameter for wet skid resistance of the SBR vulcanizates. Finally, the influence of modified fillers on the properties like abrasion resistance, tear strength and fatigue failure and the improvement in the properties have been explained in terms of polymer-filler interaction.