• Elastomers and Composites
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• v.34 no.5
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• pp.399-406
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• 1999

Polyurethane (PU) prepolymers were synthesized from polytetramethylene ether glycol (PTMG), 4,4'-diphenylmethane diisocyanate (MDI), toluene 2,4-diisocyanate (TDI) and isophoron diisocyanate (IPDI). After chain extention using dimethyol propionic acid (DMPA), aqueous polyurethane anionomers were prepared from triethyl amine (TEA) as a neutralizer. The effect of the content of chain extender and the degree of neutralization on the state of emulsification, adhesive strength, viscosity, glass transition temperature and physical properties of emulsion cast film were investigated using UTM, Viscometer and DSC.

• Elastomers and Composites
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• v.46 no.2
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• pp.158-163
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• 2011

Rigid polyurethane foam (PUF) was synthesized with different contents of aliphatic polyester polyol, aromatic polyester polyol and aliphatic polyether polyol to know change of properties under sea water. UTM(universal testing machine), DSC(differential scanning calorimetry), hardness meter and FT-IR(Fourier transform spectroscopy) were used to study the PUF`s physical properties under sea water. Compressive strength and hardness of PUF decreased with increasing the content of aromatic polyester polyol under sea water as aging. According to the results of IR spectral analysis, reduction of urethane and urea peak was found and allophanate and biuret peak increased. Although glass transition temperature of PUF increased, mechanical properties of PUF decreased under sea water, because PUF gets brittle when crosslink density increase.

• Elastomers and Composites
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• v.33 no.3
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• pp.177-184
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• 1998

Polyurethane(PU) prepolymers were synthesized from polytetramethylene ether glycol(PTMG), with 4,4'-diphenylmethane diisocyanate(MDI), toluene 2,4-diisocyanate (TDI) and isophoron diisocyanate(IPDI). After chain extention using n-methyl-diethanol amine(n-MDEA), aqueous polyurethane cationomers were prepared by addition of glycolic acid(GA) as a quaternizer. The effect of the content of chain extender and the degree of neutralization on the stability of emulsion, adhesive strength, viscosity, glass transition temperature and physical properties of emulsion cast film were investigated using UTM, viscometer and DSC.

• Elastomers and Composites
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• v.44 no.4
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• pp.423-428
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• 2009

The non-Newtonian flow curves of polyurethane melts were obtained by using a Physica cone-plate rheometer at various temperatures. The rheological parameters were obtained by applying non-Newtonian flow equation to the flow curves for polyurethane samples. When the polyurethane samples are under increasing-decreasing shear rate modes, the hysteresis loop and thixotropic behavior were shown. Polyurethane melts behave as strong gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, its shear stress remains smaller than the values measured in the increasing shear rate mode, because of broken of its structure.

• Elastomers and Composites
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• v.49 no.3
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• pp.245-252
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• 2014

FT-IR measurement and the physical properties of polyurethane adhesive prepared from the polyol, isocyanate, 2-HEMA and other acrylate monomers were examined. The softening point, viscosity, adhesion strength and mechanical properties of the PU adhesives were reviewed by Ring and Ball method, Brookfield viscometer and universal test machine, respectively. Results revealed that increment of both PPG amount and butyl acrylate content decreased softening point, adhesion strength, tensile strength and 100% modulus. However as 2-HEMA and MDI content increased the mechanical properties including tensile strength, 100% modulus increased, and also the viscosity and NCO content increased.

• Elastomers and Composites
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• v.41 no.2
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• pp.108-115
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• 2006

A series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, 1,4-phenylene diisocyanate, and hexamethylene diisocyanate with 4,4'-Bis(9-hydroxynonoxy)biphenyl (BP9). 4,4'-bis(9-hydroxynonoxy)biphenyl exhibited a smectic type mesophase. Mesophase was found for all synthesized liquid crystalline polyurethanes except 1,4-PDI/BP9 based polyurethane. Structures of the monomer and the corresponding polymers were identified using FT-IR and $^1H-NMR$ spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry and optical polarizing microscopy.

• Elastomers and Composites
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• v.47 no.2
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• pp.104-110
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• 2012

Depending on the states of polyurethane scraps generated in the production sites of polyurethane or recycling center of polyurethane scraps, appropriate recycling technologies can be employed for the recycling of resources. In this study, recycling technologies for the polyurethane scraps were classified into physical recycling, chemical recycling, and energy recycling and reports in the literatures were discussed.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.223-229
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• 2016

This study proposes a new technology for a smart damper with flag-shaped behavior using the combination of magnetic friction and rubber springs. The magnet provides friction and, thus, energy dissipation, and the rubber springs with precompression contribute to present self-centering capacity of the damper. To verify their performance, this study conducts dynamic tests of magnet frictional dampers and precompressed rubber springs. For the purpose, hexahedron Neodymium (NdFeB) magnets and polyurethane rubber cylinders are used. In the dynamic tests, loading frequency varies from 0.1 to 2.0 Hz. The magnets provide almost perfect rectangular behavior in force-deformation curve. The rubber springs are tested without or with precompression. The rubber springs show larger rigid force with increasing precompression. Lastly, this study discusses combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine the magnets and the rubber springs to obtain the flag-shaped behavior.

• Elastomers and Composites
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• v.38 no.3
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• pp.243-250
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• 2003

Polyurethane waterproof (PW) coatings are increasingly demanded in Korea for repairing cracks on old building roofs and construction of many sporting facilities. Calcium carbonate, a common filler, is incorporated in PW compositions. In this study, PW coatings were prepared by substituting a part of calcium carbonate with fly ash. The maximum amounts of calcium carbonate which can be substituted by fly ash obtained in the cyclone and bag filter dust collectors were 20 and 10%, respectively. It was found that the curing rate of PWs ran be controlled by varying the amount of Pb-octoate catalyst. The elongations at break as well as tensile strength and tear strength of PW coatings containing fly ash could also be adjusted such that their values were comparable to those of a standard PW coating by varying relative amounts of some components. However, the amount of cadmium, mercury, and lead leached from PW coatings containing fly ash obtained from the bag filter collector exceeded the respective allowed upper limits, mainly due to the initial high contents of them in the fly ash. On the other hand, PW coatings containing fly ash obtained from the cyclone collector exhibited better mechanical properties and did not release any significant amounts of the heavy metals. Thus, it was concluded that PW coatings containing fly ash can be utilized for practical applications as long as an appropriate fly ash is used.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.371-376
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• 2001

The purpose of this study is to investigate toughening of unsaturated polyester resin by addition of polyuretane liquid rubber. In general, unsaturated polyester resin has strong brittleness in spite of its high strength Therefore; it is difficult to use unsaturated polyester mortar for the place where impact resistance is demanded. In this study, it was evaluated strength and Gf by using to polyurethane liquid rubber. As a result, the toughness of unsaturated polyester mortar was increased by polyuretane liquid rubber.