Jinho Jang

Superhydrophobic PLA fabrics prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl groups

Superhydrophobic poly(lactic acid) (PLA) fabrics are prepared by UV photo-grafting of hydrophobic silica particles possessing vinyl functional groups on the surfaces, which is a novel one-step process to provide surface with roughness as well as hydrophobicity simultaneously. For this purpose, hydrophobic silica particles with vinyl groups and average diameter of 1.51+/-0.05 microm are synthesized via a sol-gel process. The silica particles possessing vinyl groups are found to be effectively immobilized on PLA fabrics via UV photo-grafting reaction. The water contact angle of the treated PLA fabric is measured to be approximately 150 degrees, which is high enough to exhibit the Lotus effect as a result of the superhydrophobicity.

Effect of UV irradiation on cellulase degradation of cellulose acetate containing TiO2

Cellulose acetate (CA) films containing anatase type titanium dioxide (TiO2) nanoparticles were prepared by solution casting. The film surface was modified by UV irradiation using a grid type UV irradiator. The UV irradiation caused slight increase in photodegradation of the CA films with TiO2 compared to the CA film alone. However, CA films irrespective of TiO2 content did not show a significant enzymatic degradation by a cellulase fromAspergillus niger without UV irradiation. Upon UV irradiation, the biodegradability remarkably improved even in the CA film without TiO2. The irradiation of CA films decreased both the water contact angle and the degree of substitution (DS) implying the decrease in acetyl groups of the CA film surface due to the photo-scission of the acetyl group and photooxidation, resulting in more facile biodegradation of the surface film layer. The substantial enhancement in biodegradation of the UV irradiated CA film containing TiO2 was attributed to the increased hydrophilicity, lowered DS and zeta potential due to the photoscission and the photooxidation effect of UV light. Also the increased surface area of the CA film due to the photocatalysis of TiO2 particles may encourage the facile biodegradation.

Effect of degree of polymerization on the mechanical properties of regenerated cellulose fibers using synthesized 1-allyl-3-methylimidazolium chloride

Abstract1-Ally-3-methylimidazolium chloride ([AMIM]Cl) was successfully synthesized and was used as a green spinning solvent for cellulose. The celluloses of various degrees of polymerization (DP) were dissolved in the [AMIM]Cl to obtain 5 % (w/w) cellulose solutions, which were regenerated to cellulose fibers through wet spinning process. Of three different regenerated cellulose fibers with different DPs, a DP of 2,730 was gave the strongest regenerated fiber without drawing having a tensile strength of 177 MPa and an elongation at break of 9.6 % respectively, indicating that celluloses of higher molecular weight can be entangled and oriented more easily. Also maximum draw ratio of the as-spun fibers increased from 1.2 to 1.7 with increasing degree of polymerization leading to a tensile strength and modulus of 207 MPa and 48 GPa, respectively. Particularly the tensile modulus was substantially higher than those of lyocell and high performance viscose fibers of 20 GPa or less. The higher DP of pristine cellulose was critical in increasing the mechanical properties such as tensile strength and elongation at break of the as-spun fibers coupled with higher tensile modulus after drawing.

The Improvement of Thermal Stability and Tensile Toughness by the Photocrosslinking of Poly(phenylene sulfide) containing Acetophenone

Poly(phenylene sulfide) films containing acetophenone as a photoinitiator were photocrosslinked under UV irradiation using a continuous UV irradiator. The gel fraction of the irradiated PPS in 1-Chloro naphthalene reached 94.7% with increasing UV energy and the photoinitiator concentration in the film upto 200J/cm 2 and 12wt% respectively. Solid state 1 C NMR analysis suggested that the crosslinking occurred between the phenylene chains in PPS, indicating that the acetophenone may abstract the phenylene hydrogens and subsequently adjacent polymer radicals could be recombined to form the crosslinked structure. The crosslinking improved the thermal behavior of PPS such as loss of Tg and Tc, higher melting point and lower melting enthalphy as well as significantly higher peak pyrolysis temperature as much as 63.5 o C. Surprisingly the tensile toughness of the most crosslinked PPS increased by 842%, resulting from the substantial enhancements in tensile modulus, strength and strain as much as 76%, 236% and 240% respectively. Also dynamic mechanical measurement indicated that the distance between crosslinks in the crosslinked PPS reached 85.3 g/mol corresponing to a crosslink density of 0.012 mol/g.

Sur face Modification of Ultra High Molecular Weight Polyethylene Films by UV/ozone Ir radiation

Ultra High molecular weight polyethylene(UHMWPE) films were photooxidized by UV/ozone irradiation. Reflectance of the irradiated films decreased in the low wavelength regions of visible light, indicating destructive interference of visible light due to roughened surface. The UV treatment developed the nano-scale roughness on the UHMWPE films surface, which increased by two-fold from 82.6 to 156.6nm in terms of peak-valley roughness. The UV irradiation caused the oxygen content of the UHMWPE film surface to increase. Water contact angle decreased from 83.2˚ to 72.9˚ and surface energy increased from 37.8 to 42.6mJ/m 2 with increasing UV energy. The surface energy change was attributed to significant contribution of polar component rather than nonpolar component indicating surface photooxidation of UHMWPE films. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the film surfaces.

Photo-oxidation and Dyeability of Poly Ketone by UV/O 3 Irradiation

Abstract: Poly ketone (PK) was photo-oxidized by UV/ozone irradiation and the effect of UV energy on the surfaceproperties of the UV-irradiated PK film was investigated by th e measurement of reflectance , surface roughness, contactangles, ESCA, and ATR. Reflectance, particularly at the wav elength of 380nm, decreased with increasing UV energy. Andthe irradiation produced nano-scale roughness on the surface uniformly. The maximum surface roughness increased from25.3nm for the unirradiated sample to 104.9nm at the irradiation of 42.4J/cm². The improvement in hydrophilicity was causedby the introduction of polar groups such as C-O and C=O bonds resulting in higher O 1s /C 1s . The surface energy of PK filmincreased from 43.3 mJ/m² for the unirradiated sample to 71.9 mJ/m² at the irradiation of 31.8J/cm². The zeta potential ofthe UV-irradiated PK decreased with increased UV energy and the dyeability to cationic dyes increased accordingly, resultingfrom the photochemically introduced anionic and dipolar dyeing sites on the PK films surfaces.

Color Deepening and Antimicrobial Finish in the Dyeing of Cotton Fabrics using Rhus verniciflua Extract

―Deep coloration of cotton fabrics with concentrated Rhus vernic iflua extract was carried out using large amount of Glaubers salt and a mordant in order to improve dyeability and functional properties such as deodorizing and antimicrobial ac tivity. With increasing in the salt addition upto 80% in the dyeing liq uor containing 0.45% extract concentration, K/S value and exhau stion increased threefold from 1.2 to 3.5, indicating that the salt r educed the electrostatic repulsion between the dyes and the cot ton fibers. Also the concentrated extract solution to 8% can increase the c olor build up upto a K/S of 11.1. In addition the combined pre- and post-mordanting methods with potassium alum enhanced the dyeabi lity upto a K/S of 22.2. The ammonia deodorizing property increased with increased color yield of the dyed fabrics. Also the dyed and post-mordanted fabrics with 8% extract concentrati on showed antimicrobial activity against both Klebsiella pneumoniae and Staphylococcus aureus .

Antimicrobial Dyeing of Cotton and Silk Fabrics Using Houttuynia cordata Extract

Cotton and silk fabrics were dyed with Houttuynia cordata extract using aqueous ethanol solution and the dyeing and post-treatment conditions were optimized to impart antimicrobial activity to the fabrics. The dried Houttuynia cordata can be extracted at for 3 hours using an aqueous ethanol solution containing 70%(w/w) ethanol. For the highest color yields. Both cotton and silk fabrics can be dyed at for 60min with 10g/L of NaCl under pH 4. Silk fabrics can be dyed to higher K/S than cotton fabrics. The color fastness properties of the dyed fabrics were good when either citric acid crosslinking or aluminum alum mordanting was carried out as a post treatment. The dyed silk and cotton fabrics with the post treatments showed excellent antimicrobial activity against both Staphylococcus aureus and Klebsiella pneumoniae.

Flame-retardant Finish of Cotton Fabrics Using UV-curable Phosphorous-containing Monomers

Abstract ― Flame-retardant cotton fabrics were prepared by UV curing of ph otocurable aqueous formulations of pho-sphorous-containing methacrylate monomers and 2-hydroxy-2-methy l-1-phenyl-1-propanone as flame retardants and a photoinitiator respectively, which is an environmentally friendly and energy-s aving process. The characterization of the UV-coated cotton fab ric was made by ATR, TGA and limited oxygen index measurement. UV c ured coating onto cotton fabrics reduced the first thermal decomposition temperature and mass loss as well as increase in the amount of char residue compared with the untreated cotton fabric presumably due to modified thermal decomposition process . The LOI values up to 28.5 and 27.2 were obtained by the UV curing of MMEP and TMEP respectively. The treatment was durable to five laundering cycles, which was more prominent in the case of trifunctional TMEP treatment. Keywords: cotton, flame retardancy, UV curing, LOI, MMEP, TMEP〈연구논문(학술)〉 자외선 경화형 인계 단량체를 이용한 면직물의 방염가공

UV-induced coloration of cotton fabrics by photografting of acrylamido dyes using acrylamide as a comonomer

Formulations of acrylamido dyes containing comonomers can be photografted onto cotton fabric upon UV irradiation at room temperature without neutral salts, which makes it a novel coloration process of excellent environmental friendliness. The photografting of the dyes can be assisted by the copolymerization of the acrylamide comonomer which may reduce the steric hindrance of the bulky dyes. About 90 % of the dyes and 94 % of the acrylamide are photopolymerized in the solution and the degree of polymerization is estimated to be 13.2 according to 1H-NMR and MALDI-TOF mass analyses. The optimal K/S values of the grafted cotton fabrics showed 13.3 and 12.3 for red and yellow dyes, respectively. The optimal UV-grafting coloration can be achieved when a UV energy of 25 J/cm2 was irradiated on the padded fabrics with a formulation of 0.65 mole ratio of acrylamide to the dyes, 7 wt% acetophenone photoinitiator (Irgacure 2959) based on the dye weight under pH 6. Furthermore, the color fastness properties of the grafted fabric were superior to those of conventional reactive dyeing of the dyes due to higher molecular weight of the polymerized dyes.