Dong-Jin Lee

Preparation and properties of segmented thermoplastic polyurethane elastomers with two different soft segments

Thermoplastic polyurethane elastomers were prepared from 4,4-diphenylmethane diisocyanate (MDI)/1,4-butanediol (BD)/poly(propylene glycol) (PPG) and MDI/BD/poly(oxytetramethylene glycol) (PTMG). The MDI/BD-based hard-segment content of polyurethane prepared in this study was of 39–65 wt %. These polyurethane elastomers had a constant soft-segment molecular weight (Mn, 2000), but a variable hard-segment block length (n, 3.0–10.1; Mn, 1020–3434). The effects of the hard-segment content on the thermal properties and elastic behavior were investigated. These properties of the PPG-based MPP samples and the PTMG-based MPT samples were compared. The polyurethane prepared in this study had a hard-segment crystalline melting temperature in the range of 185.5–236.5°C. With increasing hard-segment content, the dynamic storage modulus and glass transition temperature increased in both the MPP and MPT samples. The permanent set (%) increased with increasing hard-segment content and successive maximum elongation. The permanent set (%) of the MPP samples was higher than that of MPT samples at the same hard-segment content. The value of K (area of the hydrogen-bonded carbonyl group/area of the free carbonyl group) increased with increasing hard-segment content in both the MPP and MPT samples, and the K value of the MPT samples was higher than that of the MPP samples at the same hard-segment content.

Synthesis and properties of liquid crystalline polyurethane elastomers

Novel type of mesogenic chain extenders used in this study are N,N′-bis(4-hydroxyphenyl)-3,4,3′,4′-biphenyldicarboxyimide (BPDI) and N,N′-bis[4-(6-hydroxyhexyloxy) phenyl]-3,4,3′,4′-biphenyldicarboxyimide (BHDI). BHDI has a flexible spacer of 6-methylene units but BPDI does not. The liquid crystalline polyurethane elastomers were synthesized from BPDI or BHDI as a mesogenic chain extender, 4,4′-diphenylmethane diisocyanate, and poly(oxytetramethylene)glycol (MW 1000) as a soft segment. Polyurethane based on BHDI exhibited two melting transitions. However, any melting behavior was not shown in the BPDI-based polyurethanes because of higher melting temperature than decomposition temperature. The composition of polyurethanes was varied as a means of manipulating liquid crystalline behavior and physical properties. The BHDI-based polyurethanes containing above 50 wt % of hard segment content exhibited nematic liquid crystal behaviors. As the hard segment content of the BHDI-based polyurethanes increased, the glass transition temperature (Tg), strength, modulus, and the amount of hydrogen bonding increased.

Deodorizing and antibacterial performance of cotton, silk and wool fabrics dyed with Punica granatum L. extracts

Natural dye extracts were obtained by extraction from Punica granatum L. using water as an extractant at 90 °C for 90 min with various liquor ratios (solid Punica granatum L.(wt.): solvent water(wt.); 1:100–1:5). Dyeing was carried out using a 1:50 dyeing bath ratio at 80 °C for 60 min by exhaustion method. This study focused on the effect of liquor ratio on dyeing properties and deodorizing/antibacterial performance of various fabrics (cotton, silk and wool) dyed with Punica granatum L. extract without mordants. The optimum liquor ratio was found to be 1:10. By IR, UV-visible spectroscopies and HPLC analysis, the main component in Punica granatum L. extract and the yellow colorant component were found to be ellagic acid. By GC/MS analysis, the major volatile components of pristine Punica granatum L. powder were found to be acetic acid (area: 25.84 %), ethanol (area: 17.97 %), acetoin (area: 13.11 %), acetaldehyde (area: 8.96 %), isobutanal (area: 4.90 %). All dyed fabrics (cotton, silk and wool fabrics) displayed outstanding deodorizing performance (99 %) against ammonia gas and excellent antibacterial performance (bacteriostatic reduction rate: 99.9 %) against Staphylococcu aureus and Klebsiella pneumoniae.

Effect of blend ratio of PP/kapok blend nonwoven fabrics on oil sorption capacity.

More research and development on novel oil sorbent materials is needed to protect the environmental pollution. New nonwoven fabrics (pads) of polypropylene (PP)/kapok blends (blend ratio: 100/0, 75/25, 50/50, 25/75 and 10/90) were prepared by needle punching process at a fixed (optimized) condition (punch density: 50 punches/cm2 and depth: 4 mm). This study focused on the effect of blend ratio of PP/kapok nonwoven fabrics on oil sorption capacities to find the best blend ratio having the highest synergy effect. The PP/kapok blend (50/50) sample has the lowest bulk density and showed the best oil absorption capacity. The oil sorption capacity of PP/kapok blend (50/50) nonwoven fabric for kerosene/soybean oil [21.09/27.01 (g oil/g sorbent)] was 1.5–2 times higher than those of commercial PP pad oil sorbents. The highest synergy effect of PP/kapok blend (50/50) was ascribed to the lowest bulk density of PP/kapok blend (50/50), which might be due to the highest morphologically incompatibility between PP fibre and kapok. These results suggest that the PP/kapok blend (50/50) having the highest synergy effect has a high potential as a new high-performance oil sorbent material.

Preparation and properties of emulsifier-/NMP-free crosslinkable waterborne polyurethane-acrylic hybrid emulsions for footwear adhesives (II) – effect of dimethylol propionic acid (DMPA)/pentaerylthritol triacrylate (PETA) content

Abstract Stable emulsions (solid content: 38%) of emulsifier-/N-methylpyrrolidone (NMP)-free crosslinkable waterborne polyurethane-acrylic hybrids with a fixed acrylic monomer content (20 wt.%) and different molar ratios (mole%) of dimethylol propionic acid (DMPA)/crosslinkable pentaerythritol triacrylate (PETA)(17/23, 22/17, 27/11, 32/5) were successfully prepared. This study examined the effect of mole% of DMPA/PETA on the stability and viscosity of hybrid emulsions, the tensile properties/dynamic mechanical thermal properties of hybrid film samples and the adhesive strengths of formulated adhesives for footwear at both dry and wet states. The tensile strength/modulus, storage modulus and Tgs increased with increasing PETA content. The adhesive strength at dry state increased with increasing DMPA content up to 27 mole%, and then decreased a little. However, the adhesive strength at wet state decreased with increasing DMPA content. The optimum DMPA/PETA contents were found to be 27/11 mole% to achieve high performance adhesive properties.

Effect of Extractant on the Color Characteristics of Natural Colorant Extracts

Natural colorant extracts were obtained by extraction from tumeric root, gardenia seeds, mugwort and green tea using water, methanol, ethanol and acetone as extractants at room temperature for 3 hours under shaking condition(180rpm) with liquor ratio(solid:solvent; 1:100). The main pigment components of tumeric root, gardenia seeds, mugwort and green tea are known to be curcumin, crocin, chlorophyll b and epigallocatechin gallate, respectively. The effects of the kind of extractant and pH on the color characteristics of natural colorant extracts were investigated. The solubility parameters of pigment components were determined to find adequate extractant. The solubility parameters of curcumin, crocin, chlorophyll b and epigallocatechin gallate were found to be 27.85, 29.40, 19.48 and . As expected, solvents that have a solubility parameter similar to that of pigment component were generally found to be effective to obtain pigment extracts having high visible absorbance(A). The extract(pigment/solvent) with high visible absorbance was generally found to have low (lightness) and high Chroma(, purity).

Comparison of Oil Sorption Capacity and Biodegradability of PP, PP/kapok(10/90wt%) Blend and Commercial(T2COM) Oil Sorbent Pads

The oil sorption capacities and biodegradability of nonwoven fabrics(pads) of PP and PP/kapok(10/90wt%) blend prepared in this study and commercial pad(T2COM: 100% PP) were compared. The biodegradability(58.5%) of PP/kapok(10/90wt%) blend pad was about 5times higher than those(11%) of PP and T2COM pads after 45days. The oil sorption rates of oil sorbent pads for various oils(diesel, lubricant and Bunker C oils) were markedly increased with increasing dipping time up to about 5min and then levelled off. The oil sorption rate and oil sorption capacity were found to increase in the order of PP/kapok(10/90wt%) blend>PP>commercial(T2COM) and Bunker C>lubricant>diesel.

Effect of Coated Polypyrrole Content on the Properties of Polypyrrole Coated Fabrics

To chemically prepare polypyrrole(pPy) coated fabrics(silk, cotton and nylon fabrics), the fabrics were first soaked in 0.4M oxidant /0.06M dopant anthraquinone-2-sulfonic acid solution for 5min at room temperature, and subsequently soaked in a 0.4M monomer pyrrole aqueous solution for 5min at room temperature. The content(wt%) of coated pPy in the coated fabrics was controlled by the number of treatments(these two steps). This study examined the effect of the number of treatments/pPy content on the sheet resistance, mechanical/bending properties and color behaviors of pPy coated fabrics. The coated pPy content, sheet resistance(/square) and color strength(K/S) of pPy coated fabrics increased sharply with increasing number of treatments up to 20 times, while the increase slowed down afterward. The tensile strength, elongation at break and lightness() decreased with increasing number of treatments. The tensile modulus and bending rigidity of coated fabrics increased significantly with increasing number of treatments/coated pPy content. This indicated that the flexibility of coated fabrics decreased considerably.