• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.445-450
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• 1998

Interpenetrating polymer networks(IPNs) were prepared from castor oil-type polyurethanes(PUs) and epoxy resin. Two types of PU were prepared by using polypropylene ether glycol(PPG) as a chain extending agent and caster oil(CO) as a crosslinking agent. COPU/epoxy simultaneous interpenetrating polymer networks(SINs) based on CO had a better compatibility over the all composition than PPGPU/epoxy SINs based on PPG. The flexural strength of all PPGPU/epoxy SINs was decreased with decreasing entanglement of networks. COPU/epoxy SINs showed the higher fracture toughness and mechanial properties than the PPGPU/epoxy SINs. Fracture surfaces of all of the SINs showed the localized shear deformation and crack deflection rather than generation of stress whitening associated with the cavitation.

• Journal of Adhesion and Interface
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• v.12 no.1
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• pp.11-15
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• 2011

In this study we synthesized low VOC-solvent soluble thermo plastic polyurethane, The effect of chain extender and NCO/OH ratio for properties of thermoplastic polyurethane was investigated. Also, we prepared low VOC-type primer by TPU and acrylic modified tackifier resin. When NCO/OH ratio was 2 or more, TPU was insoluble in low VOC solvent. And peel strength was higher value using polar type tackifier than non-ploar type tackifier.

• Journal of the Korean Applied Science and Technology
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• v.29 no.1
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• pp.13-18
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• 2012

A die casting mold releasing agent was prepared from aqueous mixture of powdery carbon black and water soluble natural polymeric materials such as xanthan gum(X-gum) and carboxymethyl cellulose(CMC), which were used as thickening agent as well as curing agent with aldehydes. The suitable concentration of natural polymers for stable dispersion of carbon black in water was 0.25 wt% of X-gum or 1.0 wt% of CMC. When CMC was used less than 1 wt%, the final carbon black disperion showed a rapid phase separation. The adhesion of carbon black releasing agent on glass plate was improved with the amount of crosslinking agent, glutaraldehyde and chain extender, oligosaccharide. However, the affinity of carbon black releasing agent prepared with X-gum was stronger than that with CMC on glass plate. The final carbon black mold releasing agents prepared under our mixing conditions can be applied to the production of castings of high quality with good workability and without worthening evironmental situations.

• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.595-604
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• 1992

Carbonate-type polyurethane resins containing anionic moieties were systhesized from NCO-terminated prepolymer method. Membranes were manufactured from the polymer solution and the separation of aqueous ethanol solution was investigated. To enhance the property of urethane resin, carbonate-type polyol(PTMCG) was used. ${\alpha}^{\prime},{\alpha}^{{\prime}{\prime}}$-dimethylolpropionic acid was used as a chain extender to increase the hydrophilicily of the urethane membrane. The ionization of the pendent carboxylic groups in urethane resin was carried out using trimthylamine. To confirm the formation of anionic groups in urethane resin, IR spectra of model compounds were compared with those of urethane resins. It was confirmed that the concentration of hard segment and hydrogen bond contributed to the property of the concentration of hard segment and hydrogen bond contributed to the property of urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to urethane resin in which the mole ratio of chain extender and polyol was from 3:1 to 5:1. The carbonate-type polyurethane containing pendent carboxylic grop(PU) had Tg of around-$25^{\circ}C$ and Tm, $45^{\circ}C$ measured by DSC. Transition temperatures of one containing pendent anionic group(APU) prepared from the ionization of PU shifted to $8{\sim}10^{\circ}C$ lower temperature region than those of PU. Pervaporation membrane was prepared through the casting method. N, N-dimethylformamide (DMF) were used as a solvent and hexamethylene diisocyanate(HMDl) as a crosslinking agent. Swelling degree increased with ethanol concentration in mixure and the control of the swelling degree of the membrane could be achieved by crossliking. The results of pervaporation were as follows : separation factor, 2.3~9.8 ; flux, $27{\sim}79.5g/m^2hr$. Pervaporation separation capacity could be enhanced by reducing the molecular weight of polyol from 2,000 to 1,000.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.31-37
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• 1999

Recently, the development of propellant trends toward minimum smoke signature, insensitivity and high performance. PSAN has been used as a oxidizer for less sensitive minimum smoke propellant. Unfortunately, it provides low performance to propellant. Energetic polymers such as GAP and PGN are frequently proposed for use in minimum smoke Propellants to overcome the energy Penalty imposed by using AN as the oxidizer. In this study the mechanical properties, glass transition temperature and viscosity of PGN and EPGN binder were investigated.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.28-35
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• 2000

In this study, we investigated the characteristics of polyurethane synthesis by simultaneously measuring resonant frequency and resonant resistance with a quartz crystal analyzer. The rapid decrease of resonant frequency was appeared because automatic catalytic reaction was caused by the polyurethane formed in initial stage of polyurethane synthesis. In prepolymer(PP) synthesis, the resonant frequency was slowly stabilized after a rapid decrease at a certain point of time. But in segmented polyurethane synthesis in which chain-extender was involved, the resonant frequency increased again after a rapid decrease at a certain point of time. It was considered that this tendency took place because the chain-extender, 1,4-butandiol, caused a soft segment to change to a hard segment. The resonant resistance was used in the analysis of mechanism. From the results, the characteristics of polyurethane synthesis could be analyzed on-line using a quartz crystal analyzer, and the synthesis mechanism could also be interpreted.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.967-974
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• 1994

We studied the cure kinetics of the DGEBA(Diglycidyl ether of bisphenol A)/MDA(4, 4' -methylene dianiline)/MN(Malononitrile)/HQ(Hydroquinone) system by Barrett method and Integral method with dynamic runs of differential scanning calorimetry(DSC). Kinetic parameters such as activation energy and pre-exponential factor were obtained and reaction order was estimated roughly supposing that present system was adjusted to nth order reaction. The MN(Malononitrile) was introduced as a chain extender and HQ(Hydroquinone) as a reactive accelerator or catalyst.

• Polymer(Korea)
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• v.34 no.5
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• pp.442-449
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• 2010

Polyurethane(PU) prepolymer was synthesized from ethylene oxide/propylene oxide(EO/PO) random polyether polyol, toluene diisocyanate and chain extender such as ethylene glycol and 1,4-butanediol. PU foams having various compositions were fabricated from PU prepolymers with different hard segment contents(%) and mixed foaming solution of different compositions. PU foam from chain extender-introduced PU prepolymer and mixed foaming solution containing glycerin showed better mechanical property than other groups. Various PU foams were tested on their mechanical property, moisture vapor transmission rate, absorption speed, absorptivity, morphology and cell culture test. According to the test, the PU foam fabricated from chain extender-introduced PU prepolymer and mixed foaming solution containing optimum composition of F-68, glycerin and CMC was found to have the best property for wound dressing materials. From in vivo animal study, it was confirmed that above PU foam showed rapid wound recovery.

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.86-92
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• 2005

Poly(urethaneethyl acrylate) hybrid emulsions were synthesized to improve their thermomechanical and solvent resistance properties. In the synthesis, dimethylol propionic acid was used to impart hydrophilicity to the hybrid polymers, and ethyl acrylate monomer was added to the polyurethane prepolymer after neutralization with triethylamine. After dispersion of the neutralized prepolymer, chain extension was carried out with ethylene diamine. Consequently, poly(urethaneethyl acrylate) hybrid emulsion was prepared via soap free emulsion polymerization of ethyl acrylate with reduction-oxidation initiator couple of t-butyl hydroperoxide/sodium bisulfite at $50^{\circ}C$. Tehsile strength, 100% modulus, elongation, and solvent-resistance properties of the hybrid emulsion were measured and compared with those of polyurethane homopolymer, poly(ethyl acrylate) homopolymer, and simple blended samples.

• Elastomers and Composites
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• v.42 no.2
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• pp.93-101
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• 2007

In this study, for enhancing the durability of permeable pavement material polyurethane(PU) adhesives were developed, and the physical properties upon polymerization and additives were studied. PU polymerization followed the bulk polymerization of free solvent type considering ecological aspect. Additives used in this study were carbon black, calcium carbonate and ultra violet stabilizer. The property changes upon different environment were evaluated with the compressive strength which is the principal measurement of the property of pavement materials. Among polymerized PU, one formulated with esterpolyol and crosslinkable chain extender gave the highest compressive strength of $74.9kgf/cm^2$, better than commercial $60kgf/cm^2$. The strength was the highest when the material specimen contained carbon black and calcium carbonate 20 wt%, respectively. However, UV stabilizer did not show good weathering properties.