• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.388-396
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• 2008

2 Components polyurethane coatings are widely used for the industrial coating in general because of its excellent film performance and the workability which were brought by the 3 dimensional cross linked chain structures being formed after the reaction between polyol and polyisocyanate. 2 components polyurethane can be classified into alkyd polyol, polyester polyol, acrylic polyol and polyester modified acrylic polyol depending on where it is used. This research was conducted under the conditions below; different chemical compositions of resin for paint, set the same conditions of viscosity, thinner and acid value, set alternative polyols, OH values and catalysts, set alternative polyisocyanate hardeners of the paint, measure the reaction rates and dynamic mechanical characteristics using RPT-3000, Rotation Rheometer, DMA and FTIR. The research found that the reactivity between polyol and isocyanate influences the film performance and workability depending on the catalysts, OH values and chemical compositions. We find out that different reaction rate of acrylic polyol and polyester modified acrylic polyol with poly-isocyanate is not influenced on temperature and catalyst. In addition, reaction speed of high hydroxyl content polyol is faster than low hydroxyl equivalent. These results can improve difficult working condition to apply urethane coating.

• Journal of Adhesion and Interface
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• v.16 no.1
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• pp.22-28
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• 2015

In this study, Waterborne polyurethanes (WPU) using Epoxy group were synthesized with polyester polyol, epoxy resin, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), dimethylol propionic acid (DMPA) to improve the hydrolysis resistance and adhesion. In addition, the properties of the synthesized waterborne polyurethane was evaluated through DSC, UTM, adhesion strength. Tg of the synthesized waterborne polyurethane is shown in the vicinity of $-50^{\circ}C$. Tg were increased with as epoxy resin contents increased. The tensile strength was increased as the content of epoxy resin increases, elongation was decreased. Optimum adhesion and hydrolysis-resistance strength were obtained when polyol : epoxy ratio was 99 : 1.

• Journal of Adhesion and Interface
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• v.11 no.3
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• pp.100-105
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• 2010

In this study, polyurethane dispersion was prepared by polyester polyol, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), dimethylolpropionic acid (DMPA), and monomeric diol. The effect of various monomeric diol, polyol/monomeric diol molar ratio and DMPA contents on the properties of polyurethane dispersion were investigated. As the molecular weight of monomeric diol and monomeric diol molar ratio increased, $T_g$ gradually increased. And when DMPA contents increased, also $T_g$ gradually increased. In the results of mechanical properties, when the molecular weight of monomeric diol, monomeric diol molar ratio of polyol/monomeric diol and DMPA contents increased, tensile strength was increased. Finally, optimum peel strength obtained when polyol/monomeric diol ratio was 8 : 2.

• Elastomers and Composites
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• v.52 no.1
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• pp.81-85
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• 2017

In order to improve the water resistance, we synthesized waterborne polyurethane by using polyester polyol, poly(propylene carbonate) (PPC), 4,4'-dicyclohexylmethane diisocyanate ($H_{12}MDI$), and dimethylolpropionic acid (DMPA). The properties of the synthesized waterborne polyurethane using poly(propylene carbonate) (WPUP) were evaluated by FT-IR, $^1H-NMR$, GPC, DSC, TGA, and UTM. The mechanical properties increased while the adhesion properties decreased with the increase in the amount of PPC. The highest water resistance was shown when the ratio of polyester polyol to PPC was 9:1.

• Polymer(Korea)
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• v.26 no.2
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• pp.193-199
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• 2002

The dichloro-polyester polyol (DCBAO) which was synthesized in our earlier work was cured at room temperature with two different type of curing agents including Desmodur N-3300 and Desmodur L-75 to get a polyurethane flame-retardant coatings (DCBAO/N-3300=DEBAN and DCBAO/L-75=DCBAL). We could not observe any deterioration of physical properties of the flame-retardant PU coatings (UCBAN and DCBAL) in comparison with the conventional PU coatings. Thermal resistance of DCBAL-type flame-retardant coatings, which was measured by yellowness index difference, was inferior to that of DCBAL-type PU coatings. We believe that this phenomena is attributed to the poor thermal resistance of Desmodur L-75 isocyanate. It was observed that the LOI values were 25∼26% for the PU coatings containing 20∼30 wt% of 2,4-dichlorobenzoic acid.

• Journal of Adhesion and Interface
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• v.22 no.2
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• pp.39-46
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• 2021

Waterborne polyurethanes (WPU) was synthesized using polyester polyol and polycarbonate polyol containing 3-Methyl-1,5-pentanediol (MPD) in a branched structure. To compare physical properties, WPUs were synthesized using polyester polyol obtained from 1,4-butanediol (BD) and adipic acid and polycarbonate polyol obtained from 1,6-hexane diol (HD)/ 1,4-butanediol (BD). This study investigated the effect of polyol molecular structure (molecular structure in soft segments) on the physical properties of WPUs. In the case of WPUs synthesized using polyols containing MPD, 100% modulus and tensile strength were lower than that without MPD, and elongation was higher. The transparency of WPU films with MPD were slightly better than WPU films without MPD.

• Applied Chemistry for Engineering
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• v.19 no.5
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• pp.547-553
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• 2008

To achieve the ideal performances of paint film, resins and hardeners have to be chosen and designed in a proper way depending on the exposure circumstance of substrate and the requested physical properties. Six different kinds of clear paints were made in this experiment using alkyd polyol, polyester polyol, polyester modified acrylic polyol and another 3 acrylic polyol resins whose $T_g$ and OH value were partially modified. Then the tests for chemical, physical, and mechanical properties were measured after forming the paint films using aliphatic and aromatic polyisocyanate. The viscosity and elasticity of paint film were then measured in terms of gel point and $tan{\delta}$ using Rheometer and DMA. Through this viscoelastic characteristic test of polyurethane resin, we were able to choose the adequate resins and hardeners which are the most important in the top and primer painting system of urethane paint and, as a result of observing the physical, mechanical, and chemical properties of paint film by urethane, we have finally reached the conclusion that we could apply the proper polyol to top and primer paint for developing the polyurethane paint system.

• Journal of the Korean Institute of Gas
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• v.12 no.3
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• pp.38-42
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• 2008

Effect of polyol structure and NCO index on adhesion of PU adhesive at room ($25^{\circ}C$) and extremely low temperature ($-190^{\circ}C$) was investigated. At room temperature adhesive strength of PU adhesive tends to decrease as molecular weight of polyol increases, however, the strength at $-190^{\circ}C$ shows opposite tendency. Adhesive strength of the PU turned out to be directly proportional to the amount of MDI. PU containing aliphatic polyol was higher in shear strength at $-190^{\circ}C$ and the strength of PU with aromatic polyol was higher at room temperature.

• Clean Technology
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• v.25 no.1
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• pp.7-13
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• 2019

Recently, attention has been paid to obtaining bio-polyols from renewable resources. Successful use of these natural ingredients successfully produced in the industry for the synthesis of various polyurethanes is a very important task. In this study, a series of dimethylformamide (DMF) based polyurethanes were synthesized from methylene diphenyl diisocyanate (MDI)/1, 4-butanediol and bio-polyol (polytrimethylene ether glycol based on 1, 3-propanediol : B-POL)/polyester polyol (polyadipate diol based on 1,4-butandiol : H-PET). The effect of different ratio of bio-polyol (B-POL)/polyester polyol (H-PET) on the physical properties of polyurethane was investigated. As the B-POL content in B-POL/H-PET mixture increased, the glass transition of soft segment (Tgs) and tensile strength of polyurethane decreased, however, the elongation at break and tear strength increased. On the other hand, artificial leather was produced by wet process using synthesized DMF-based polyurethanes. It was found that there was almost no difference in the effect of the B-POL/H-PET composition on the average size and density (the number of cells per unit volume) of the porous cells formed in artificial leather. These results show that there is no problem in using bio-polyol (B-POL) based polyurethane for artificial leather produced by wet process.

• Journal of Adhesion and Interface
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• v.17 no.2
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• pp.67-71
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• 2016

In this study, low-viscosity polyurethane hot-melt were synthesized with polyether polyol / polyester polyol, 4,4-dicyclohexylmethane diisocyanate ($H_{12}MDI$), 2-butanone oxime (MEKO) to improve the properties and peel strength. The properties of the synthesized low-viscosity polyurethane hot-melt was evaluated through FT-IR, viscosity meter and UTM. When the content of the reactive diluent increases and the NCO-blocked prepolymer decreases, the viscosity of low-viscosity polyurethane hot-melt adhesive was increased. When the ratio of OH-terminated oligomer, NCO-blocked prepolymer and content of reactive diluent is 1 : 0.5 : 0.5, low-viscosity polyurethane hot-melt showed 1.1 kgf/cm peel strength.