Jae Hwan Chun

Synthesis and properties of polyurethane coatings: the effect of different types of soft segments and their ratios

Polyurethane (PU) coatings were prepared using siloxane polyol [poly(dimethyl siloxane), PDMS], polyether polyol [poly(propylene oxide glycol), PPG], and polyester polyol [poly(tetramethylene adipate glycol), PTAd]. The PTAd/PPG ratio was altered, whereas the PDMS content was fixed during PU synthesis. The structural elucidation of the synthesized PU was performed by Fourier transform infrared (FT-IR), 1H NMR, 13C NMR, and 29Si NMR spectroscopic techniques. The PU-film surface was characterized by X-ray Photoelectron Spectrometer and atomic force microscopy techniques and it was found that the surface smoothness depended on the PPG/PTAd ratio. The PU melting temperature, crystallinity, mechanical properties (tensile strength and Young’s modulus), and adhesive strength were also depended on the PPG/PTAd ratio. The adhesive strength to poly(vinyl chloride) of the coating with the proper polyol ratio (PTAd 12.50 mol% and PPG 16.67 mol%) was almost unaffected after immersion (three months) in artificial salt.

Synthesis of Poly(methylene oxy-alt PPO)glycols and Its Effect on the Properties of Polyurethane UV-Cured Film

In this study, we synthesized MPPG including the methylene-oxy group from polypropylene glycol (PPG) with the molecular weight (g/mol) of 200. Also UV curable resins were prepared from the mixture of polyurethane acrylate (PUA) oligomer which was synthesized with synthesized MPPG, TMPTA, HDDA, and HP-8 to investigate the possibility of its application for optical film materials. The Tg was higher for UAMP oligomer with MPPG as well as MPPG than that of PPG and UAP oligomer. The refractive index and the pencil hardness of UCM were higher than those of UC while the optical transmittances of UCM and UC were much the same.

Preliminary studies of polyurethane adhesive for thermoplastic polyolefins(TPOs) using polyolefin polyol

ABSTRACT To develop a halogen-free polyurethane adhesive for thermoplastic nonpolar polyolefins, polyurethanes were synthesized by using polyester polyol, polyolefin polyol, 4,4′-dicyclohexylmethane diisocyanate, and isophorone diamine, The properties of the resulting polyurethanes were evaluated by Fourier transfer infrared spectroscopy, differential scanning calorimetry, and a universal testing machine. As the polyolefin polyol content increased, the elongation and Tg of the synthesized polyurethane increased, while the tensile strength decreased. However, the highest adhesive strength, 6 times of polyester polyol-based one, was obtained when the ratio of polyester polyol to polyolefin polyol was 8: 2.

Chloroprene rubber modified by nanosilica for performance adhesion strength

ABSTRACT In this study, chloroprene rubber (CR) /silica nanocomposites prepared by dispersing nanosilica in CR was applied as a primer and its adhesion properties were examined. The structure of CR/silica nanocoposite was analyzed by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to confirm the morphology and silica content of the CR/silica nanocomposite. The SEM results indicated that the sample prepared with a silica content of 4 phr was the most homogenously dispersed. Contact angle and pencil hardness measurements indicated that the hydrophobicity and the hardness of the CR/silica nanocomposite increased with increase in the silica content. The peel strength was the highest at a silica content of 4 phr, and the initial peel strength of P-4 sample (2.9 kgf/inch) was 50% higher than that of the P-0 sample.

Coating properties of UV-curable polyurethane acrylate composites with lotus leaf powder

ABSTRACT Eco-friendly water-repellent UV-curable polyurethane acrylates (PUA) with fluorine groups were synthesized from H12MDI which is excellent yellowing resistance and water resistance, polycarbonate diol, perfluoropolyether (PFPE) diol, and 2-hydroxyethyl acrylate. As increasing to 10% PFPE in polyol content, the contact angle of the cured PUA increased from 75.9∘ to 107.1∘ while tensile strength decreased and elongation increased due to the flexibility of PFPE. To improve their hydrophobicity, composites were prepared by adding small amounts of lotus leaf powder (LLP). The obtained PUA/LLP composite with 2% LLP showed much hydrophobicity, 120.6∘ of contact angle but their mechanical properties were not affected by adding LLP.

Synthesis and property of polyurethane using poly(oxyalkylene-alt-PPO) glycols

ABSTRACT As a new diol, poly(oxyalkylene-alt-PPO) glycols including the methylene-oxy group from polypropylene glycol (PPG) were newly synthesized by the phase transfer catalysis. Waterborne polyurethanes (WPUs) with different contents of the modified polyol as a soft segment were synthesized. We investigated the possibility of their application for optical film materials. Comparing to PPG-based WPU, the Tg of poly(oxyalkylene-alt-PPO) glycols-based WPU increased and the refractive index and the pencil hardness were higher than those of PPG-based WPU while the optical transmittances were almost the same. These indicate that poly(oxyalkylene-alt-PPO) glycols-based WPU can be used for optical protect film.

Synthesis of β-hydroxyalkylamide by using microwave and its performance for powder coating

ABSTRACT Among the curing hardeners for powder coating, β-hydroxyalkylamide is widely used due to its easy handling, excellent exterior durability, good mixing with other chemicals, flexibility, hardness, and especially non-toxic property. In this study, β-hydroxyalkylamide which is normally produced by oil bath heating was synthesized by microwave heating system. For synthesis, it takes 300 min of reaction time for heating system of oil bath but the microwave heating requires only 100 min of reaction time because of the internal heating. Performances of products obtained by both heating systems showed very similar properties. These results suggest that the microwave as a heating source is an effective tool for the reaction of β-hydroxyalkylamide.

Syntheses and properties of waterborne polyurethane-epoxy adhesives

ASBTRACT In this study, waterborne polyurethanes (WPUs) with an epoxy group and improved hydrolysis resistance and adhesion were synthesized using a polyester polyol, epoxy resin, 4,4-dicyclohexylmethane diisocyanate, and dimethylol propionic acid (DMPA). The properties of the WPU were evaluated by differential scanning calorimetry, tensile strength, elongation, hardness and adhesion strength. The glass transition temperature (Tg) of the synthesized WPU was approximately −50°C. The Tg and tensile strength increased with increasing epoxy resin content while the elongation decreased. The optimum adhesion was achieved with a polyol:epoxy ratio of 99:1.

Preparation and Characterization of UV Cured Optical Films Containing a Fluorene Compound

In this study, the high refractive coating films applicable for optical materials were produced. the conversion and the photo curing behaviors were examined through FTIR-ATR and photo-DSC, and thermal and mechanical properties of cured films were examined by using DMA and UTM, and pencil hardness, refractive index and optical transmittance of film were measured. Urethane metacrylate oligomer was synthesized by mixing bisphenoxyethanolfluorene (BPEF), polycaprolactone diol (PCL), and polytetramethylene ether glycol (PTMeG) in varying ratios. Also, as the results of mixing ethylene glycol phenyl ether acrylate (PHEA) and trimethylolpropanetriacrylate (TMPTA) in varying ratios, the more time UV irradiated, the higher conversion and the heat of enthalpy (ΔH) and the initial curing rate increased with increasing TMPTA content up to 70%. Also, as the trifunctional monomer increased, the storage modulus and Tg increased, and the stress increased while the strain decreased to reach its maximum value. Also, as the BPEF ratio increased, the maximum value of stress increased while the strain decreased, the refractive index and pencil hardness increased, and light transmittance was all over 80%.

Water-induced surface structure of poly(dimethylsiloxane)-containing block copolymers

AbstractTwo triblock copolymers, polyester-b-poly(dimethylsiloxane) (PDMS)-b-polyester, were synthesized by the ring-opening polymerization with both hydrophobic and water-repellent hydroxyl-terminated PDMS and hydrolytically degradable ester monomers. The Tgs of the polyester blocks were controlled by ɛ-caprolactone/lactide mixture or lactide only. The surface composition of the triblock copolymers was measured by angle-dependent electron: X-ray photoelectron spectroscopy. The results showed that the PDMS block with a low surface energy in the copolymers was quite segregated in the surface region; the copolymer films showed significantly higher mole fractions of PDMS (0.78–0.86) at a low takeoff angle compared with their bulk mole fractions (0.015–0.02). When the films were exposed to water at 20 °C for 70 min, the mole fractions of surface PDMS were decreased to 0.3–0.5 because of the water-repellent hydrophobicity and the chain mobility of both blocks.