• Elastomers and Composites
• /
• v.54 no.4
• /
• pp.294-298
• /
• 2019

A three-layered PVC sheet consisting of polyvinyl chloride (PVC) and woven polyester fabric was prepared by extrusion and calendering. The flexibility and durability of the PVC were tuned by adding plasticizers, additives, and surface coatings. The tensile and tear strengths of the three-layered PVC sheet were higher than those of commercial two-layered sheet, while exhibiting low weight. The concentrations of the total volatile organic compounds (TVOCs) and formaldehyde (HCHO) emitted from the sheet were also lowered. The PVC sheet remained stable after prolonged exposure to UV light, signifying that the PVC sheet is suitable for cargo screen applications.

• Elastomers and Composites
• /
• v.46 no.2
• /
• pp.138-143
• /
• 2011

EPDM compounds and vulcanizates containing inorganic filler such as talc, calcium carbonate, or clay as well as carbon black were prepared, and the influence of inorganic filler on properties of the EPDM compounds and vulcanizates were investigated. The bound rubber contents did not significantly increase even though the inorganic filler was added. There were big aggregates in the EPDM samples with high loading inorganic filler. By adding the inorganic filler, the cure times tended to increase and the delta torque decreased. The modulus were on the whole decreased, whereas the elongation at break, tensile strength, and tear strength were increased by adding the inorganic filler. The decreased modulus and increased elongation at break can be explained with the decreased delta torque, the increases of tensile strength and tear strength can be explained with the increased elongation at break. By adding the inorganic filler, level of reinforcing in the EPDM compounds did not increase and the crosslink density decreased.

• Journal of Adhesion and Interface
• /
• v.9 no.2
• /
• pp.24-31
• /
• 2008

In this work, calcium hydroxide and magnesium carbonate as metal ionic crosslinking agents were used to introduce ionic crosslinking points to the ethylene vinylacetate (EVA) emulsions for the enhancement of water resistance and mechanical properties of emulsion films. The properties of EVA emulsion film were investigated in crosslinking density, thermal features, surface energy, and mechanical properties, such as tensile strength, elongation at break and tear strength. With the increasing content of metal ionic crosslinking agent, the crosslinking density of the EVA emulsion film increases, resulting into the improvement of water resistance. The surface energy and mechanical properties of the EVA emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.4% for calcium hydroxide and 0.5% for magnesium carbonate was added respectively, because the EVA emulsion containing carboxylic acid forms strong carboxylate-metal bond of ionically-crosslinked system. Therefore, it can be concluded that metal ionic crosslinking agents, such as magnesium carbonate and calcium hydroxide are considered to improve water resistance and mechanical properties of the EVA emulsion.

• Elastomers and Composites
• /
• v.40 no.1
• /
• pp.12-21
• /
• 2005

In this work, magnesium carbonate and calcium hydroxide as metallic crosslinking agent were added to chlorosulfonated polyethylene rubber (CSM) emulsion to enhance the mechanical properties of emulsion film such as tensile strength, elongation at break, and tear strength and crosslinking density, thermal features, and surface energy were also investigated. Crosslinking density of the CSM emulsion film with increasing the amount of magnesium carbonate and calcium hydroxide increased, leading to the enhancement of water resistance. It was shown that compared with calcium hydroxide, magnesium carbonate had a little higher crosslinking density and $T_g$ value. The surface energy and mechanical characteristics of the CSM emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.75% for magnesium carbonate and 1.0% for calcium hydroxide were added respectively. Therefore, it can be concluded that as metallic crosslinking agent to improve water resistance and mechanical properties of the CSM emulsion, magnesium carbonate is more preferable to calcium hydroxide.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.30 no.2
• /
• pp.55-61
• /
• 1998

This treatment was applied to bleached softwood kraft pulp handsheets in an effort to improve physical strength of paper. Paper strength was improved by esterification of cellulose and polycarboxylic acid. Because hydrogen bond of carboxyl group is stronger than that of hydroxyl group, polycarboxylic acid forms stronger hydrogen bond than cellulose does. 1,2,3,4,-cyclopentanetetracarboxylic acid (CPTA) and sodium dihydrogen phosphate ($NaH_2O_4$) were used as polycarboxylic acid and catalyst, respectively This reaction was confirmed by the weight gain of the handsheets, by FTIR spectrum and by changes in mechanical properties of sheets. Wet tensile strength was improved when handsheets were treated with polycarboxylic acid. However, tear strength and burst strength decreased.

• Journal of Mechanical Science and Technology
• /
• v.15 no.1
• /
• pp.35-43
• /
• 2001

Both tensile and tear properties of short-fiber reinforced Chloroprene rubber have been studied as functions of the fiber aspect ratio and fiber content. Both properties increased when both the fiber aspect ratio and fiber content were increased. The fiber reinforced rubbers exhibited maximum values of these properties at a fiber aspect ratio of about 300. When the fiber aspect ratio exceeds 400, the mechanical properties decreased with the fiber content because of the non-uniform dispersion of fibers. The tensile modulus was compared with the prediction by the Halpin-Tsai equations for randomly oriented cases. A bonding agent was used in the fiber treating process. It was found that the ultimate tensile strength, torque, tearing energy and tensile modulus of the rubbers with treated fibers were much higher than those with untreated ones.

• Clinics in Shoulder and Elbow
• /
• v.2 no.2
• /
• pp.99-105
• /
• 1999

We investigated the effectiveness of arthroscopic decompression in stage Ⅱ subacromial impingement after long term follow up. Arthroscopic subacromial decompression was done in 104 consecutive patients who had stage Ⅱ sub­acromial impingement. After average of 8.4 years follow up, the final results were as following; 57 shoulders(55%) in excellent, 25(24%) in good, 16(15%) in fair and 6(6%) in poor. All parameters-pain, function, muscle strength and motion-were improved significantly(p<0.00l). Rotator cuff tear was developed in 10 shoulders after decompression. Among them, 8 shoulders had unfavorable results including two poor. In 6 failures, two had rotator cuff tear, three had recurrence of impingement with degenerative change and reflex sympathetic dystrophy was developed in one. Reoperations were done in 4 shoulders. Improvement of impingement symptoms was maintained in the most of patients(79%) after long term follow up. Arthroscopic decompression surgery was very effective means for stage Ⅱ impingement syndrome.

• Clinics in Shoulder and Elbow
• /
• v.11 no.2
• /
• pp.71-76
• /
• 2008

The pathophysiology of rotator cuff tears and the progression of asymptomatic tears to symptomatic tears are yet unclear and much controversy. It is likely to involve a number of factors such as a genetic predisposition, extrinsic impingement from structures surrounding the cuff and intrinsic degeneration from changes within the tendon itself. Degenerative changes in the rotator cuff with aging seem to be related to the anatomic and mechanical environment of the rotator cuff. The histopathologic appearance of rotator cuff tendon rupture specimens demonstrates a consequence of degenerative changes at the site of tendon insertion into bone. It weakens the tensile strength of the tendon. Is the process of degeneration intrinsic or extrinsic in nature? I suggest that degeneration is intrinsic and not caused by extrinsic factors. Even though, rotator cuff tear may be secondary to multiple factors, I believe that primary cause of rotator cuff tears is preexisting degenerative change.

• Clinics in Shoulder and Elbow
• /
• v.27 no.3
• /
• pp.327-337
• /
• 2024

Background: Anterior combined latissimus dorsi and teres major (aLDTM) tendon transfer has shown promise as a treatment for anterior superior irreparable rotator cuff tears (ASIRCTs). Our study aimed to compare aLDTM clinical outcomes for ASIRCTs between young and elderly patients. Methods: This retrospective study reviewed data from patients who underwent aLDTM tendon transfer for ASIRCTs with minimum 2-year follow-up. Clinical evaluations included visual analog scale (VAS), American Shoulder and Elbow Surgeons (ASES) score, Single Assessment Numeric Evaluation (SANE), active range of motion (aROM), strength, and complications. Radiologic assessments included acromiohumeral distance, Hamada classification, and integrity of transferred tendon. Patients were divided into group total (all ages), group old (≥70 years), and group young (≤60 years). Results: A total of 123 patients were enrolled with 39 in group young (mean age, 56.6±4.9 years) and 27 in group old (mean age, 73.6±2.3 years). Postoperatively, both groups showed significant improvements in VAS, ASES, and SANE scores and improved aROM for forward elevation, abduction, and internal rotation. No significant differences in clinical coutcomes were noted between the groups. Furthermore, similar rates of complications, including retears and postoperative infections, were observed across all three groups. Conclusions: Our study highlights the effectiveness of aLDTM transfer for ASIRCTs with minimal glenohumeral arthritis, demonstrating similar outcomes in both group young and group old patients. Moreover, patients in these distinct age groups showed comparable clinical results when compared to group total.

• Advances in materials Research
• /
• v.8 no.2
• /
• pp.103-115
• /
• 2019

Polypropylene (PP) fibers for making fabric which is used for packing cement have a high strength and high tear resistance. Due to these excellent properties the present study investigates the effect of PP fibers on the mechanical strength of concrete. Mechanical strength parameters such as compressive strength, splitting tensile strength and flexural strength are evaluated. Structural integrity of concrete using Ultrasonic Pulse Velocity (UPV) was also studied. Concrete containing PP fibers in percentage of 0%, 0.15%, 0.25%, 0.5% and 0.75% was developed with a characteristic compressive strength of 25 MPa. Concrete cubes, cylinder and prismatic specimens were cast and tested. It was found that the UPV values recorded for all specimens were of the similar order. Test results indicated the used of PP fibers can significantly improve the flexural and splitting tensile strengths of concrete materials whereas it resulted a decreased in compressive strength. The relative increase in split tensile and flexural strength was optimum at a fiber dosage of 0.5% and a mild decreased were observed in 28 days compressive strength. The findings in this paper suggested that PP fibers deriving from these waste cement bags are a feasible fiber option for fiber-reinforced concrete productions.