• Journal of Adhesion and Interface
• /
• v.7 no.1
• /
• pp.3-9
• /
• 2006

Three isocyanate groups of IP-$75^{(R)}$ and one hydroxyl group of various amino alcohols were applied for preparing cationic type water-borne polyurthane (PU) having ionic center onto flexible side chains. Average particle size, dispersion stability, viscosity, contact angle, surface energy, glass transition temperature ($T_g$), and adhesion strength of prepared water-borne PUs were measured and analyzed with different NCO/OH mol ratios, ionomers, and neutralizing agents. It was characterized that the prepared PU has a smaller particle size and a better dispersion stability than the conventional cationic water-borne PU containing ionic centers onto main chains.

• Elastomers and Composites
• /
• v.58 no.3
• /
• pp.121-127
• /
• 2023

The effect of diisocyanate type on the decomposition temperature of polyurethane (PU) hydrolysis was investigated in a subcritical water medium up to 250℃. PU samples were prepared using different types of diisocyanate: two aromatic diisocyanates (4,4'-methylene diphenyl diisocyanate (MDI) and methyl phenylene diisocyanate (TDI)), one unbranched aliphatic diisocyanate (hexamethylene diisocyanate (HDI)), and two cyclic aliphatic diisocyanates (4,4'-methylene dicyclohexyl diisocyanate (H₁₂MDI) and isophorone diisocyanate (IPDI)). The pressure had no effect on hydrolysis in the range of 70-250 bar. The decomposition temperature of the PU samples increased in the following order: TDI-PU (199℃) < H₁₂MDI ≈ IPDI ≈ HDI (218-220℃) < MDI-PU (237℃). This order of increase in temperature is related to the electron-donating ability of the group to connected to the nitrogen of the urethane unit. When the temperature of the (PU + water) mixture reached the specific decomposition temperature, the PU samples hydrolyzed completely within 5 min into primary amine and 1,4-butanediol. The hydrolysis products from MDI-PU and H₁₂MDI-PU were separated into a liquid phase rich in (BD + water) and a solid low phase rich in amine, whereas the products from TDI-, IPDI-, and HDI-PU existed in a single aqueous phase.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.3
• /
• pp.1479-1487
• /
• 2011

In the field of the entire electronic component industry including mobile IT products, the importance of a versatile package with the multifunctional or high capacity memories is gradually increased. Multi Chip Package which has several chips in a single package is frequently used for that purpose. In MCP, epoxy adhesive films play a major role in adhesion between the chips or between chip and substrate. A series of silane coupling agents with a functional group such as epoxy, amine, mercaptan, and isocyanate were applied to the epoxy adhesives and material properties such as wettability and reliability of the adhesives were investigated. From the results, the silane coupling agent with an epoxy functional group showed highest wettability and peel strength in epoxy adhesive. For those reasons, it lead to a superior reliability in the epoxy adhesive against interfacial fracture behaviors through moisture resistance test.

• Journal of the Korean Applied Science and Technology
• /
• v.25 no.3
• /
• pp.322-331
• /
• 2008

In order to synthesize high-solid coatings, acrylic resins (HSAs) containing 90% solid content were first synthesized, then the synthesized HSAs were cured with a curing agent, isocyanate, at room temperature to obtain high-solid coatings. In the HSAs synthesis, conversion was in a range of $82{\sim}87%$, and viscosities and number-averaged molecular weight ($M_n$) of the HSAs were in a range of $4380{\sim}8010$ cP and $1540{\sim}1660$, respectively. From the correlation between $T_g$ value, viscosity and $M_n$, it was found that, with increasing $T_g$ value, viscosity increases rapidly and molecular weight increases slowly. From the visco-elasity measured by the pendulum method, it was found that the curing time decreased with increasing $T_g$ values. From the tests of physical properties of the coatings' film, $60^{\circ}$ specular gloss, impact resistance and heat resistance were proved to be good and pencil hardness, drying time and pot-life were proved to be poor.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.795-802
• /
• 2012

Surface modification of a hydrophobic acrylic polymer film has been performed through simple chemical treatment to give a reactive surface. 2-Triphenylstannylthioethyl acrylate was polymerized under UV-illumination with various contents of a comonomer. When the polymer film was treated with fluoride ion, thiol functional group (SH) was generated on the film surface, which was observed through infrared absorption spectroscopy. The surface was functionalized by thiol addition reaction to acrylic chromophores. The SH content on the surface was controlled with a comonomer, tris(hydroxymethyl)ethane triacrylate, and examined with UV-Vis absorbance of the chromophore attached film. Similarly, a polymer film from 2-tributylstannylthioethyl acrylate was prepared. Destannylation from the triphenylstannyl and tributylstannyl surface completed after 30 and 5 min, respectively. The SH-exposed surface was modified with an isocyanate attached chromophore within 10 min, while acrylic chromophore required 24 h.

• Journal of Microbiology and Biotechnology
• /
• v.11 no.2
• /
• pp.259-265
• /
• 2001

Staphylococal infection still remains to be one of the most serious infections, having various complications in the clinical use of indwelling polymeric medical devices. However, there are a few promising systems showing a high antibacterial effect without causing any demage of polymer backbone under biological environments such as blood or body fluid. In order to resolve this problem, we have designed a new antibiotic releasing system via a hydrolysis mechanism. The surface of biomedical polyurethane (PU) was modified by using 1,6-diisocyanatohexane (HMDI) to immobilize the rifampicon. Also, the immobilized rifampicin was designed to be released by a selective cleavage of the unstable carbamate linkage that exists on the rifampicin-immobilized polyurethane (PHR). The immobilization of rifampicin on the surface of polyurethane was confirmed by the disappearance of the characteristics IR absorbance peak of the isocyanate (-NCO) group at $2,267\;cm^{-1}$. The PHR showed a continuous rifampicin release profile under an aqueous environment of 10 mM of PBS (phosphate-buffered saline) for ove 6 days. The rifampicin molecules, which are released from PHR under an optimal bacterial infection environment, had a higher antibacterial activity against both S. aureus and S. epidermidis than rifampicin-incorporated polyurethane (RIP). In addition, the PHR maintained a stable antibacterial effect under a blood-mimic aqueous environment such as bovine calf serum.

• Journal of Adhesion and Interface
• /
• v.3 no.2
• /
• pp.1-8
• /
• 2002

Polyurethane NCO prepolymers were synthesized with the polyols such as PTMG, GP and the isocyanate such as TDI at $40^{\circ}C$ for 8.5 minutes. As average molecular weights (${\bar{M_n}}$: 1000, 2000, 3000, 4000) of PTMG, and GP were decreased from 4000 to 1000, ratio of oil gelation increased from 298%, to 440%, for Bunker B. When oil and water were emulsified, the ratio of gelation was increased approximately two times. Ratio of gelation for emulsive Bunker B was increased from 402% to 910%, for PTMG1000 and increased from 440%, W 958% for GPI1000. Ratio of oil gelation for emulsive Bunk C which has higher viscosity than Bunker B was measured w 923% for PTMG1000 made with chain extender, i.e. EG, and measured to 1098% for GP1000. The gel made from GP which has three functional group showed soft and strong characteristic, as a result, it can be removed easily from oil spilled ocean.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.208-209
• /
• 2011

In this work, we developed self-assembled monolayers (SAMs) of alkanethiols on gold that can release amine groups, when an electrical potential was applied to the gold. The strategy was based on the introduction of the electroactive carbamate group, which underwent the two-electron oxidation with simultaneous release of the amine molecules, to alkanethiols. The synthesis of the designed thiol compounds was achieved by coupling isocyanate-containing compound with hydroquinone. The electroactive thiols were mixed with hydroxyl-containing alkanethiol [$HS(CH_2)_{11}OH$] to form mixed monolayers, and cyclic votammetry was used for the characterization of the release. The mixed SAMs showed a first oxidation peak at +540 mV (versus Ag/AgCl reference electrode), demonstrating irreversible conversion from carbamate to hydroqinone with simultaneous release of the amine groups. The second and third cycles showed typical reversible redox reaction of hydroquinone and quione: the oxidation and reduction occurred at +290 mV and -110 mV, respectively. The measurement of ToF-SIMS further indicates that electrochemical-assisted chemical reaction successfully released amine groups. This new SAM-based electrochemistry would be applicable for direct release of biologically active molecules that contain amine groups.

• Journal of the Korean Chemical Society
• /
• v.17 no.4
• /
• pp.275-285
• /
• 1973

The addition of one mole of aluminum chloride to three moles of sodium borohydride in tetrahydrofuran gives a turbid solution with enormously more powerful reducing properties than those of sodium borohydride itself. The reducing properties of this reagent were tested with 49 organic compounds which have representative functional groups. Alcohols liberated hydrogen immediately but showed no sign of hydrogenolysis of alkoxy group. Aldehydes and ketones were reduced rapidly within one hr. Acyl derivatives were reduced moderately, however, carboxylic acids were reduced much more slowly. Esters, lactones and epoxides were reduced readily than sodium borohydride or borane. Tertiary amide was reduced slowly, however, primary amide consumed one hydride for hydrogen evolution but reduction was sluggish. Aromatic nitrile was reduced much more readily than aliphatic nitrile. Nitro compounds were inert to this reagent but azo and azoxy groups were slowly attacked. Oxime was reduced slowly but isocyanate was only partially reduced. Disulfide and sulfoxide were attacked slowly but sulfide and sulfone were inert. Olefin was hydroborated rapidly.

• Polymer(Korea)
• /
• v.37 no.4
• /
• pp.507-512
• /
• 2013

A graphene/waterborne polyurethane (WPU) nano composite was prepared by in-situ polymerization of PU and graphene having isocyanate (iGO) group in order to improve physicochemical/electrical characteristics. The properties of the graphene/WPU nanocomposite can effectively be enhanced as compared pristine WPU; up to 57% of tensile strength and $10^2$ fold of electrical conductivity with introduction of 2 wt% graphene. In addition, mechanical/electrical properties of the graphene/WPU nanocompsite were higher than those of graphene/WPU composite prepared by a simple physical blend method. It might attribute to homogeneous dispersion of iGO in the WPU matrix via covalent bonds and hydrogen bonds between WPU and iGO from the results of morphological analysis by scanning electron microscopy (SEM).