• Elastomers and Composites
• /
• v.43 no.1
• /
• pp.18-24
• /
• 2008

An oligomeric diol was utilized as a modifier for the reaction rate and mechanical properties of a RT-castable polyurethane elastomer. Both the reaction rate and the tensile strength of the blend samples, in which the modifier and the base resins were mixed with one-shot method, showed an exponential decrease as the increase of modifier concentration. Thermal analysis method of Kissinger was also effectively applied in the present study, showing good linearity in the plot of ln $(q/T^2_p)$ vs. $(1/T_p)$ and activation energy $E_a$ of 44.80 kJ/mol, which is similar to the general castable polyurethane. In the mechanical properties, remarkable decrease of strength was found by the addition of modifier concentration range up to about 20 phr, while characteristic elongation property of the elastomer, high elongation at lower strength, was observed over 20 phr of the modifier. Exponential decrease of the break strength of the blend sample exhibited that the mechanical properties of the blend might be considerably sensitive to the modifier concentration.

• Elastomers and Composites
• /
• v.39 no.1
• /
• pp.71-76
• /
• 2004

4,4'-Methylenebis(2-chloroaniline)(MOCA) has been widely used as a crosslinking agent, but classified as a toxic chemical. Thus, its use will be limited in the near future. In this research, polyurethane coating films were prepared using 1,3-propanediolbis(4-aminobenzoate)(PDBA) as an alternative to MOCA. The base part was prepared by melting MOCA or PDBA in polyoxypropylene($M_n$=2000), followed by the addition of the various additives. The NCO-terminated toluene diisocyanate prepolymer was used as a curing agent. The polyurethane coating films were prepared by mixing the base part with the curing agent in an appropriate ratio at room temperature. The polyurethane coatings prepared using PDBA exhibited higher initial viscosity, but much longer pot lift, compared to those prepared using MOCA under the same conditions, due to lower reactivity of PDBA. The tensile strength and tear strength of the coating films were much weaker. However, the pot life, tensile strength, elongation, and tear strength of the coating films, prepared using PDBA in the presence of an increased amount of Pb(II)-octoate, were close to those of the coating films prepared using MOCA. Thus, it was concluded that PDBA can substitute MOCA in the preparation of polyurethane coatings as long as the reactivity of PDBA is enhanced using appropriate amounts of the catalyst or other appropriate catalyst.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.5
• /
• pp.5-12
• /
• 2014

Weatherstrip coatings of urethane and silicon type which are fit to EPDM and thermoplastic materials are used in sealing systems for automotive applications for noise reduction and high slip characteristics for external applications, respectively. Polyurethane binder was successfully synthesized from poly(butyladiphate)diol (PBAD), poly(tetramethylene)glycol (PTMG) and isocyanate as starting materials. Then, polyurethane coating agents were prepared by using various additives. To investigate effects of segment types on the abrasion resistance of polyurethane coating agents, thin films based on polyurethane coating materials were fabricated. With increasing the amount of hard segment in the coating agent, abrasion resistance, modulus and tensile strength of the coating films were improved, but the elongation of the coating films was decreased.

• Elastomers and Composites
• /
• v.35 no.4
• /
• pp.296-302
• /
• 2000

The surfaces of injection and pressure-molded sheets of poly(ethylene-covulylacetate)(EVA) foams used for shoe mid-sole were treated with low temperature plasma to improve adhesion with a water-based polyurethane adhesives. Several experimental variables were considered, such as radio frequency power, treating time, type of gas. gas flow, and distance between electrode and sample. The modificated surface by plasma treatment were characterized using contact angle meter, scanning electron microscopy(SEM), universal testing machine(UTM). Adhesion was tested by T-peel tests of treated EVA foams/polyurethane adhesive joints. The treatment in the low temperature plasma produced a noticeable decrease in contact angle. The peel strength of EVA foams treated with plasma was increased with plasma treating time, and gas flow.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.1
• /
• pp.139-146
• /
• 2002

This study deals with the characterizing and the application like as insulation materials in the joint part in concrete surface layer and waterproofing sheet especially for roof slabs. Using steel materials and butil-rubber tape to band waterproofing sheet and concrete surface together before this waterproofing system will be applied. It can be expected to both the curability and the watertightness by coating poly-urethane 2 or 3 times with sheet surface. Therefore this waterproofing system can be possible to protect water without the damage when vapor is going out from concrete and without air pockets because of the difference temperature inside and out. This system particularly consists of air bents and elastic waterproofing sheet considering the physical damage while water can cause purely physical damage. This system is one of the most efficient ways of waterproofing system without air pocket.

• Journal of Adhesion and Interface
• /
• v.14 no.3
• /
• pp.121-127
• /
• 2013

In this work, the thermoplastic polyurethane (TPU) was melt-blended with EPDM, NBR and BR to form TPU/Rubber blend films, their composition and friction-induced surface fracture relationship was investigated. TPU/EPDM and TPU/BR blends exhibited the improved friction-induced surface fracture, especially the effect of BR was excellent. With addition of more than 10 wt% BR, TPU/BR blends exhibited the improved friction-induced surface fracture. The increase of the soft segment with increasing BR content, which was confirmed by scanning electron microscopy (SEM) analysis enabled us to estimate the improved friction-induced surface fracture.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.3
• /
• pp.229-236
• /
• 2017

The purpose of this study is to investigate the behavior and characteristics of rubber springs and calculate the compressive stiffness by performing dynamic compression tests of rubber springs. In order to carry out the dynamic compression test of rubber spring, total 9 rubber springs were tailored by calculating the shape factor of L80-D55, L90-D58, and L100-D60, and used for the experiments. Experiments were performed by controlling the compression according to the length of the rubber spring, and the compression was increased in the order of 5%, 10%, 15%, 20% and 25% of the strain. From the experimental results, the force-strain curves were obtained and it was confirmed that strength decrease and strength increase phenomenon occurred as the strain increased. In addition, it was confirmed that the decrease of stiffness and the increase of stiffness were clearly observed according to the size and diameter of the rubber spring, and the effective compression stiffness was estimated using the slope of the force-strain curve. By using the effective compressive stiffness, design values that can be used in actual design were presented.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.4
• /
• pp.469-480
• /
• 2006

The goal of this study is to ases the static and dynamic behavior of disk bearings under railway vehicle loadings. Several static tests were conducted in a laboratory t bearings, all having the same kind of polyurethane disk as used in the static tests, were installed under a full-sized railway bridge and tested with a running locomotive, the tests results, the static and dynamic stiffness of the disk bearings were estimated and compared. the deformation of the disk bearings under the bridge was measured at varying disk bearing was almost half of that under dynamic loading. In addition, the dynamic stiffness of the fixed disk bearing was 80% higher than that of an expansion disk bearing, since the PTFE in the expansion bearing is displaced. The deformation of the disk bearing did not vary significantly with changes in locomotive's speed. The results of this study can contribute to fast-tracking the formulation of a design technique for disk bearings for railway bridges.

• Elastomers and Composites
• /
• v.47 no.3
• /
• pp.238-245
• /
• 2012

Graphene oxide was synthesized from natural graphite, and its surface was modified using diisocyanatodicyclohexylmethane( $H_{12}MDI$). Isocyanate-graphene sheet(i-RGO) was obtained by reduction of surface modified GO. To select nanofiller having good dispersion with polyurethane, GO, i-RGO, natural graphite and thermal reduced graphite were analyzed, and then i-RGO was selected as a suitable nanofiller. PU/i-RGO nanocomposite was synthesized with various i-RGO contents to estimate effect of reinforcement on nanocomposite. Thermal stability, hardness, contact angle were increased with i-RGO contents due to i-RGO characteristic and crosslink bridge effect. But, tensile strength and elongation were decreased at i-RGO contents more than the 4 wt%. This phenomenon was interpreted by the excess formation of crosslink bridge.

• Elastomers and Composites
• /
• v.39 no.3
• /
• pp.209-216
• /
• 2004

Two types of polyurethane-acrylate polymer were synthesized by reaction of 2-hydroxyethyl methacrylate(HEMA), acrylamide(AA), and polyurethane prepolymer. Water-soluble cationic polyurethane/acrylate retention aids were prepared by using polyurethane-acrylate, benzyl chloride and distilled water. The retention, drainage and strength properties of the retention aids were investigated. The retention of cationic polyurethane/acrylate type retention aids maintained around 70 % regardless of nm. COD value of white water was much reduced by adding the retention aids to it. Drainage property was also improved by addition of the retention aids. In addition, specific compression strength of the paper was improved a little by addition of the retention aids. PU-HEMA type showed better performance than PU-AA in terms of compression strength of the paper.