• Polymer(Korea)
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• v.39 no.2
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• pp.281-286
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• 2015

UV-cured acrylic copolymer pressure sensitive adhesive (PSA) having different amounts of crosslinking agents were prepared and adhesion properties were investigated. 0.01 wt% of MMT clay was dispersed in 2-ethylhexyl acrylate (2-EHA)/acrylic acid (AA) monomer mixture containing 0, 0.05, 0.1 and 0.3 wt% 1,6-hexandiol diacrylate (HDDA) for crosslinking. It was investigated that the curing behavior and surface chemistry of PSAs were merely affected by the presence of MMT clays. On the other hand, adhesive properties were influenced by the MMT addition; a cohesive failure was restrained due to improved molecular elasticity even in uncrosslinked acrylic PSAs. However, it was also appeared that combination of 0.3 wt% crosslinking agent and MMT loading might result in the damage of adhesion properties of PSAs possibly due to the lack of chain flexibility. In our studies, it is suggested that the 2-EHA/AA PSAs incorporating 0.01 wt% of MMT and crosslinked with 0.05 wt% of HDDA exhibited the balanced adhesion properties without severe cohesive failure during strip.

• Geomechanics and Engineering
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• v.25 no.2
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• pp.143-157
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• 2021

Expansive soil is the most predominant geologic hazard which shows a large amount of shrinkage and swelling with changes in their moisture content. This study investigates the macro-mechanical and micro-structural behaviours of dredged natural expansive clay from coal mining treated with ordinary Portland cement or hydrated lime addition. The stabilised expansive soil aims for possible reuse as pavement materials. Mechanical testing determined geotechnical engineering properties, including free swelling potential, California bearing ratio, unconfined compressive strength, resilient modulus, and shear wave velocity. The microstructures of treated soils are observed by scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy to understand the behaviour of the expansive clay blended with cement and lime. Test results confirmed that cement and lime are effective agents for improving the swelling behaviour and other engineering properties of natural expansive clay. In general, chemical treatments reduce the swelling and increase the strength and modulus of expansive clay, subjected to chemical content and curing time. Scanning electron microscopy analysis can observe the increase in formation of particle clusters with curing period, and x-ray diffraction patterns display hydration and pozzolanic products from chemical particles. The correlations of mechanical properties and microstructures for chemical stabilised expansive clay are recommended.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.466-477
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• 1994

PEG 600-diglycidyl ethers(PDE) were synthesized using $BF_3$ catalyst by the reaction of epichlorohydrin and PEG 600 which is known to have the hygroscopicity, softening property, and antistatic property. Water-soluble long chain polyamines(PDET) were synthesized by coreaction of PDE and triethylenetetramine which is high conductive aliphatic amine curing agent. To prevent the gelation of the PDET and increase the water-solution stability, water-soluble quaternary ammonium polyamines were synthesized by cationation of PDET with acetic acid. Antistatic agents PDET-2A, PDET-5A, PDET-6A, PDETA-2A and PDETA-4A were prepared by the mixing of PDET-2, PDET-5, PDET-6, PDETA-2 and PDETA-4 with water. Synthesized antistatic agents were treated on PET textiles with and without resin. Then surface electrical resistivity and half life characteristics value were tested. As the results there were no remarkable decreasing changes in antistatic abilities of the textiles treated with PDETA-2A and PDETA-4A after 50 times washing. So PDETA-2A and PDETA-4A were proved to be durable antistatic agents. Surface electrical resistivity of the textiles treated with PDETA-2A and PDETA-4A before washing were $1{\times}10^7{\Omega}$ and $2{\times}10^7{\Omega}$, respectively, and half life characteristics values were 0.8sec and 1.1sec, respectively. Therefore PDETA-2A and PDETA-4A were proved to be good antistatic agents.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.345-356
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• 1994

Each of the three cationized compounds synthesized previously, poly(OMA-co-DAMA)[PODC], poly(DMA-co-DAMA)[PDDC] and poly(EMA-co-DAMA)[PEDC] was blended with waxes, emulsifiers and cationized fatty carbamide(ODTCC) synthesized in this study for the preparation of some durable softening water-repellenting agents, PODCW, PDDCW and PEDCW. The results of washability, tearing strength, crease recovery and contact angle of the cotton fabrics treated with PODCW, PDDCW and PEDCW with and without textile finishing resin, showed remarkable improvement of the physical properties. Rating of water repellency of cotton fabric treated with PODCW was 80, but those treated with PDDCW and PEDCW were not high enough to use in industry. Proper curing temperature of the synthesized water-repelleting agents was $140^{\circ}C$; proper using concentration was 3wt%; sodium acetate was the best catalyst for water-repellenting agents among the used, and proper concentration was 0.6wt%. From the results of reaction mechanism of cellulosic fiber with water-repellenting agent and washability of the fibers treated with water-repellenting agents the prepared water-repellenting agent proved to be durable. Surface structures of cotton fabrics treated with water-repellenting agent were investigated by SEM.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.694-700
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• 2017

Clostridium difficile, which causes pseudomembranous colitis, releases toxin A and toxin B. These toxins are considered to be the main causative agents for the disease pathogenesis, and their expression is associated with a marked increase of apoptosis in mucosal epithelial cells. Colonic epithelial cells are believed to form a physical barrier between the lumen and the submucosa, and abnormally increased mucosal epithelial cell apoptosis is considered to be an initial step in gut inflammation responses. Therefore, one approach to treating pseudomembranous colitis would be to develop agents that block the mucosal epithelial cell apoptosis caused by toxin A, thus restoring barrier function and curing inflammatory responses in the gut. We recently isolated an antimicrobial peptide, Periplanetasin-2 (Peri-2, YPCKLNLKLGKVPFH) from the American cockroach, whose extracts have shown great potential for clinical use. Here, we assessed whether Peri-2 could inhibit the cell toxicity and inflammation caused by C. difficile toxin A. Indeed, in human colonocyte HT29 cells, Peri-2 inhibited the toxin A-induced decrease in cell proliferation and ameliorated the cell apoptosis induced by this toxin. Moreover, in the toxin A-induced mouse enteritis model, Peri-2 blocked the mucosal disruption and inflammatory response caused by toxin A. These results suggest that the American cockroach peptide Peri-2 could be a possible drug candidate for addressing the pseudomembranous colitis caused by C. difficile toxin A.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.1-7
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• 2015

The objective of this study is to develop a high-performance foamed concrete made with a new mixture proportioning as an alternative of autoclaved lightweight concrete (ALC) block. For the early-strength gain of the foamed concrete under an atmospheric curing condition, the binders and chemical agents were specially contrived as follows: 3% anhydrous gypsum was added to ordinary portland cement (OPC) in which $3CaO{\cdot}SiO_2$ content was controlled to be above 60%; and the content of polyethylene glycol alkylether in a polycarboxylate-based water-reducing agent was modified to be 28%. Using these binders and chemical agents, 11 mixes were prepared with the parameters of W/B ratio (30% to 20% in a interval of 2.5%) and unit binder content ($400kg/m^3$ to $650kg/m^3$ in a interval of $50kg/m^3$). The quality and availability of the mixed foamed concrete were examined according to the minimum requirements specified in the KS for ALC block and existed conventional foamed concrete. The measured properties satisfied the minimum requirement of KS for ALC block and proved that the developed high-performance foamed concrete had considerable potential for practical application.

• Fibers and Polymers
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• v.4 no.4
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• pp.182-187
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• 2003

Low molecular weight copolymers of maleic anhydride and vinyl acetate were prepared to develop formaldehyde free cross-linking agents. Since lower molecular weight is favorable for efficient penetration of the finishing agent into the cotton fibers in the padding process, the concentration of the initiator, chain transfer agent and the monomer ratios were varied to obtain copolymers of low molecular weights. The prepared polymers were characterized by GPC, $^1{H-NMR}$, FTIR, DSC and TGA. Copolymers of molecular weights of 2 000 to 10 000 were obtained and it was found that the most efficient method of controlling the molecular weight was by varying the monomer ratios. Poly(maleic anhydride-co-vinyl acetate) did not dissolve in water, but the maleic anhydride residue hydrolyzed within a few minutes to form poly(maleic acid-co-vinyl acetate) and dissolved in water. However, the maleic acid units undergo dehydration to form anhydride groups on heating above ${160}^{\circ}C$ to some extent even in the absence of catalysts. The possibility of using the copolymers as durable press finishing agent for cotton fabric was investigated. Lower molecular weight poly(maleic anhydride-co-vinyl acetate) copolymers were more efficient in introducing crease resistance, which appears to be due to the more efficient penetration of the cross-linking agent into cotton fabrics. The wrinkle recovery angles of cotton fabrics treated with poly(maleic anhydride-co-vinyl acetate) copolymers were slightly lower than those treated with DMDHEU and were higher when higher curing temperatures or higher concentrations of copolymer were used, and when catalyst, $NaH_2$$PO_2$, was added. The strength retention of the poly(maleic anhydride-co-vinyl acetate) treated cotton fabrics was excellent.

• Computers and Concrete
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• v.19 no.4
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• pp.357-363
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• 2017

This paper conveys the effects of fly ash and silica fume incorporated in concrete at various replacement ratios on the durability properties of concretes. It is quite well known that concrete durability is as much important as strength and permeability is the key to durability. Permeability is closely associated with the voids system of concrete. Concrete, with less and disconnected voids, is assumed to be impermeable. The void system in concrete is straightly related to the mix proportions, placing, compaction, and curing procedures of concrete. Reinforced concrete structures, particularly those of subjected to water, are at the risk of various harmful agents such as chlorides and sulfate since the ingress of such agents through concrete becomes easy and accelerates as the permeability of concrete increases. Eventually, both strength and durability of concrete reduce as the time moves on, in turn; the service life of the concrete structures shortens. Mineral additives have been proven to be very effective in reducing permeability. The tests performed to accomplish the aim of the study are the rapid chloride permeability test, pressurized water depth test, capillarity test and compressive strength test. The results derived from these tests indicated that the durability properties of concretes incorporated fly ash and silica fume have improved substantially compared to that of without mineral additives regardless of the binder content used. Overall, the improvement becomes more evident as the replacement ratio of fly ash and silica fume have increased. With regard to permeability, silica fume is found to be superior to fly ash. Moreover, at least a 30% fly ash replacement and/or a replacement ratio of 5% to 10% silica fume have been found to be highly beneficial as far as sustainability is concerned, particularly for concretes subjected to chloride bearing environments.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.580-585
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• 2006

UV-thermal dually curable coating materials were prepared by the sol-gel method. Nano-sized colloidal boehmite was treated with various organo silane coupling agents. These materials could be well dispersed in various alcohols and relatively polar organic solvents such as tetrahydrofuran and acetonitrile. The coating films were prepared by a spin coating method on various substrates, which were characterized by FT-IR, Si/Al CP MAS NMR spectra, UV-Vis spectrophotometer, FE-SEM, Taber abraser, haze meter, and pencil hardness tester. The effects of molar ratio and types of silane coupling agents, curing method and ion-shower treatment were investigated. Dually curable coating method offered an optimally good quality film in both hardness and transmittance. The transparency and the hardness of the prepared films were increased with amounts of 3-(trimethoxysilyl)propylmethacrylate, and (3-glycidyloxypropyl)trimethoxysilane, respectively. The adhesion between coated layer and substrate could be enhanced by ion-shower treatment.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.3 s.151
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• pp.481-486
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• 2006

There are attempts to utilize Hanji for apparel material, but, the reason that the strength and durability of Hanji decrease to a great extent in the wet condition, restricts the usability of Hanji. In order to improve the resistance against water, Hanji was treated with silicone type water repellent agents. The treatment was carried out by conventional pad-dry-cure method. The optimum treatment condition was obtained by varying the concentration of repellent agent, curing temperature and time. Water repellency was tested by spray rating method. Wet and dry tensile strength, tearing resistance and abrasion resistance were examined after the treatment. Flexural stiffness and wrinkle recovery angles of hanji were also measured. In result, the optimum condition of treatment was at resin concentration of 40g/l, catalyst concentration of 20g/l(half of resin concentration), curing temperature of 160$^{circ}C$, curing time of 120 sec. Flexural stiffness of Hanji was hardly increased and wrinkle recovery angle of Hanji was improved a little by resin treatment. After the treatment, in dry condition, tensile strength and tearing resistance were little changed but abrasion resistance was improved. In wet condition, tensile strength, tearing strength and abrasion resistance were improved.