• Macromolecular Research
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• v.17 no.7
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• pp.458-463
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• 2009

Polyurethane (PU) is widely used as a cardiovascular biomaterial due to its good mechanical properties and hemocompatibility, but it is not adhesive to endothelial cells (ECs). Cell adhesive peptides, GRGDS and YIGSR, were found to promote adhesion and spreading of ECs and showed a synergistic effect when both of them were used. In this study, a surface modification was designed to fabricate an EC-active PU surface capable of promoting endothelialization using the peptides and poly(ethylene glycol) (PEG) spacer, The modified PU surfaces were characterized in vitro. The density of the grafted PEG on the PU surface was measured by acid-base back titration to the terminal-free isocyanate groups. The successful immobilization of pep tides was confirmed by amino acid analysis, following hydrolysis, and contact angle measurement. The uniform distribution of peptides on the surface was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). To evaluate the EC adhesive property, cell viability test using human umbilical vein EC (HUVEC) was investigated in vitro and enhanced endothelialization was characterized by the introduction of cell adhesive peptides, GRGDS and YIGSR, and PEG spacer. Therefore, GRGDS and YIGSR co-immobilized PU surfaces can be applied to an EC-specific vascular graft with long-term patency by endothelialization.

• Journal of KSNVE
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• v.8 no.6
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• pp.1093-1102
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• 1998

The success of controllability of smart structures depends on the quality of the bonding along the interface between the main structure and the attached sensing and acuating elements. Generally, the analysis procedures neglect the effect of the interfacial bond layer or assume that this bond layer behaves like viscoelastic material. Three different bond layers. two modified epoxy adhesives, and one isocyanate adhesive were prepared for their toughness and moduli. Bond layer of the chosen adhesive provides an almost perfect bonding condition between the composite structure and the PZT while bended significantly like arrow-shape. The perfect bonding condition is tested by considering various material properties of the bond layers. and based on this perfect bonding condition, the effects of the interfacial bond layer on the dynamic behavior and controllability of the test structure is experimentally studied. Once the perfect bonding condition is achieved. dynamic effects of the bond layer itself on the dynamic characteristics of the main structure is negligible. but the contribution of the attached PZT elements on the stiffness of the multi-layered structure becomes significant when the thickness of the bond layer increased.

• Journal of the Korean Applied Science and Technology
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• v.25 no.4
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• pp.525-532
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• 2008

To prepare a solution type acrylic pressure-sensitive adhesive, quarter polymers were synthesized from butyl acrylate(BA), 2-ethylhexylacrylate(2-EHA) as a base monomer, methyl methacrylate(MMA) as a comonomer, each of methacrylic acid(MAA), acrylic acid(AA) as a functional monomer. Acrylic solution type pressure-sensitive adhesives(PSA's) of isocyanate derivative crosslinking PSA's were prepared by crosslinking of BEMM, BEMA with toluene-2,4-diisocyanate. The structure of adhesive was identified by FT-IR. The viscosity was measured by using Brookfield DV-III and molecular weight was measured by using gel permeation chromatography. The physical properties of polyethylene film coated with BEMMT, BEMAT were measured as a function of the concentration. As the result, BEMMT(0.6, 0.8), BEMAT(0.6) showed peel adhesion of $160{\sim}180\;g_f$/25 mm width and shear adhesion of more than 24 hours, and tackiness of $4/32{\sim}6/32$ which was relevant to commercial usage.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.12-16
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• 2016

Toluene-free pressure sensitive adhesives were synthesized by using butyl acrylate (BA), 2-hydroxy ethyl acrylate, methyl methacrylate, acrylic acid (AA) as monomers and ethyl acetate as a solvent. The polymerization recipes were designed by changing 1, 3, 5 part per hundreds monomer (phm) of AA content on the basis of 100 BA parts. Two crosslinking agents, ethyl glycol diglycidyl ether (EDGE) and isophorone diisocyanate (IPDI) were added to the synthesized polymers to increase adhesion due to crosslinking. In the measurement of properties, holding power, peel strength, and initial tackiness increased with AA content due to crosslinking between carboxyl group in AA and epoxy group in EDGE and isocyanate group in IPDI. In the comparison of two crosslinking agents, EDGE showed better in the three properties than IPDI by better reaction of epoxy group of EDGE to carboxyl group of AA.

• Journal of Forest and Environmental Science
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• v.31 no.2
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• pp.119-125
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• 2015

This study examined the effects of rice straw steaming time and mixing ratio between rice straw and wood particle on the properties of mixed particle board from Acacia mangium Willd wood and rice straw. Rice straw and Acacia mangium Willd wood were collected in Hanoi, Vietnam. The particle board was three-layer particle board with the structural ratio of 1:3:1. The thickness, density and board size of the particle board were 18 mm, $0.7g/cm^3$, and $800{\times}800{\times}18$ (mm, including trimming), respectively. A resin mixture between commercial Urea-formaldehyde (U-F) adhesive and methylene diphenyl isocyanate (MDI) adhesive was used with a dosage of 12% for the core layer and 14% for the surface layer. In this experimental design, the steaming time for rice straw was 15, 30, 45, 60, and 75 minutes at $100^{\circ}C$. The rice straw-wood mixing ratio was 10, 20, 30, 40, and 50%. The results showed that both mixing ratio and steaming time affect the properties of the particleboard, but the mixing ratio has a stronger impact. A higher mixing ratio and a longer steaming time resulted in a better quality of particleboard. The optimal steaming time for rice straw was 46.12 minutes with the straw-wood mixing ratio of 29.85% with the following characteristics of the particle board: the modulus of rupture (MOR) of 14.64 MPa, internal bond strength (IB) of 0.382 MPa, thickness swelling (TS) of 8.83%, and board density of $0.7-0.7g/cm^3$.

• Journal of the Korean Wood Science and Technology
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• v.33 no.1 s.129
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• pp.87-96
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• 2005

This study was carried out to evaluate the shear bond strength and adhesive bond durability of structural glued laminated timber (glulam) manufactured with mixed species lumber of Korean red pine, Korean pine and Japanese larch, using resorcinol adhesive and water-based polymeric-isocyanate adhesive (WPI). Each board used as a glulam lamina was graded by visual inspection. The visual lumber grade of the all species was very low due to the large size and number of knots and the steep slope of grain. In view of the results, appropriate pruning, sawing and drying processes might be needed to produce high grade lamina lumber with small knot size and drying defect free. Shear bond strength of every tested glulam specimen ranged between 7.9 and $9.9N/mm^2$, and much higher than the Korean Standard (KS) for glulam shear bond strength, $7.1N/mm^2$. There was not much shear bond strength difference between wood/resorcinol and wood/WPI. The resorcinol adhesive bond durability exceeded KS requirements. However, delamination on the end-grain surfaces of WPI glulam submerged in both room temperature and boiling water severely occurred, and its durability did not meet KS requirements. Further investigations may be required, and special care should be taken, to ensure long service life of WPI glulam used for exterior application. Results of this study are expected to be useful for improvement of mechanical properties and structural performance of mixed species glulam.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.46-51
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• 2010

Polyorganosiloxane modified polyurethane (PDMS-PU) polymers were prepared from copolymerization of ${\alpha}$,${\omega}$-hydroxypropyl terminated polyorganosiloxane with isophorone diisocyanate (IPDI), polypropylene glycol (PPG), and 2,2-bis(hydroxymethyl) propionic acid (DMPA). Hydrophobic polyorganosiloxane was introduced in polyurethane main chain as soft segment block unit. The isocyanate groups in PDMS-PU block copolymer was blocked with 2-butanon oxime and obtained PDMS-PU dispersions in water by neutralizing with triethylamine (TEA). The deblocking temperature of PDMS-PU polymer was measured from thermal analysis. The good stability of the PDMS-PU dispersion was obtained by dispersing into water. PDMS-PU prepolymers were prepared with various contents of DMPA under [NCO]/[OH] = 1.12~1.53 equivalent ratio. Increasing DMPA from 7.2, 13.4, and 18.7 mole% in preparation of PDMS-PU polymer, particle sizes were decreased from 156, 100, 65 dnm. Also contact angle and adhesive strength were measured.

• Journal of the Korean Wood Science and Technology
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• v.48 no.2
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• pp.196-205
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• 2020

The purpose of this study was to investigate a method for improving the physical and mechanical properties of laminated board made from oil palm trunk (OPT). The effects of pretreating the lamina with heat-pressure and altering the lamina composition of the laminated board were investigated. The outer third of OPT in cross-section had high-density wood, while the underlying third had low to medium density. The hot press was applied to pretreat the lamina that had low to medium density. The lamina were 1.5 cm in thickness, 5 cm in width, and 65 cm in length. The hot press was applied at 2.94 MPa or 4.41 MPa at 150 ℃ for 60 minutes, and the target thickness of the lamina was 1 cm. The three layers of the laminated board samples were bonded with isocyanate adhesive at a glue spread of 300 g/㎡ and cold pressed at 0.98 MPa for 3 h. The laminated board samples were tested according to Japanese Agricultural Standard (JAS) 234-2003. The results showed that the densification of the inner lamina did not significantly affect the physical-mechanical properties of the laminated board produced. However, the laminated board made with high-density laminas for the outer layers fulfilled the JAS 234-2003 standard for the modulus of elasticity and the modulus of rupture.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.156-167
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• 2015

The aim of this study was to determine the physical and mechanical properties of glued laminated timber (glulam) manufactured from small-diameter logs of three wood species, Acacia mangium (mangium), Maesopsis eminii (manii), and Falcataria moluccana (sengon), with densities of 533, 392, and $271kg/m^3$, respectively. Glulam measuring 5 cm by 7 cm by 160 cm in thickness, width, and length, respectively, was made with three to five lamina, or layers, and isocyanate adhesive. The glulams contained either the same wood species for all layers or a combination of mangium face and back layers with a core layer of manii or sengon. Solid wood samples of the same size for all three species were included as a basis for comparison. Physical-mechanical properties and delamination tests of glulam referred to JAS 234:2003. The results showed that the properties of same species glulam did not differ from those of solid wood, with the exception of the shear strength of glulam being lower than that of solid wood. Wood species affected glulam properties, but three- and five-layer glulams were not different except for the modulus of elasticity. All glulams were resistant to delamination by immersion in both cold and boiling water. The glulams that successfully met the JAS standard were three- and five-layer mangium, five-layer manii, and five-layer mangium-manii glulams.

• Journal of the Korean Wood Science and Technology
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• v.35 no.6
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• pp.108-117
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• 2007

This research was performed to investigate the feasibility of bamboo as a raw material for the manufacture of plywood. Wood veneer-bamboo zephyr composite boards (WBCB) were manufactured using keruing (Dipterocarpus sp.) veneers and hachiku bamboo (Phyllostacbys nigra var. henonis Stapf) using various adhesives, and the effect of the method and amount of resin spread on the mechanical properties of the composites were investigated. The WBCB manufactured using polymeric isocyanate (PMDI) showed the best mechanical properties, followed by phenol-formaldehyde resin (PF), phenol-melamine-formaldehyde resin, urea-melamine-formaldehyde resin, and urea-formaldehyde resin. However, considering the operation feasibility as well as mechanical properties, PF resin proved to be the appropriate adhesive for the practical purpose. As the amount of resin spread increased, the mechanical properties of 5-ply WBCB with 12 mm thicknesses manufactured using PF resin tended to increase, and more failure occurred at the interface between veneer and bamboo zephyr than at the interface among bamboo zephyrs. This result suggests that penetration of resin into bamboo zephyr could be the important factor. In this research, the appropriate amount of resin amount was $320g/m^2$. 5-ply WBCBs were manufactured using various methods of resin spread but the effect of the methods on the mechanical properties showed no little difference, which meant that the method of resin spread could be chosen considering the manufacturing conditions and operation feasibility.