Chemical cross-linking was introduced to enhance the mechanical and thermal properties of thermoplasic elastomer, i.e., polyurethane. By changing the amount of cross-linking agent added, cross-linking density was controlled and relationship between the internal structure and mechanical properties has been studied. Polyurethane used in this study consists o 4, 4'-diphenyl-methane diisocyanate (MDI), 1, 4-butanediol as a hard segment and polytetramethylene glycol (PTMG MW=1000 g/mol) as a soft segment. Cross-linking agent having free isocyanate functional groups at both chain ends was prepared with PTMG (MW=1000 g/mol) end-capped with MDI. By melt-blending the polyurethane with cross-linking agent in an extruder at 200℃∼220℃, allophanate functional groups were expected to form through chemical reaction between the N-H group in the hard segment and free isocyanate group in the cross-linking agent. Four samples having 0%, 10%, 15%, 20% (w/w) cross-linking agent were prepared. From stress-strain curve, the mechanical properties and hysteresis behavior of four samples were evaluated. And the effect of cross-linking on the degree of phase separation was studied with the DSC and FTIR-ATR measurements. Using synchrotron small angle X-ray scattering method, thermal stability of hard domain was investigated. upon cross-linking, mechanical properties were observed to be enhanced, however, the thermal stability was lowered.

The effect of biodegradable modified aliphatic polyester (MAP) on neat tetrafunctional epoxy (4EP) was investigated in terms of cure kinetics, thermal stabilities, and rheological properties. The 4,4'-diamino diphenyl methane (DDM) was used as a curing agent for the blend system and the content of 4EP/MAP was varied with the in the 100:0, 90:10, 80:20, 70:30, and 60:40 wt%. As a result, the cure activiation energies ($E_{a}$) for the cure kinetics obtained by dynamic DSC method using Kissinger equation, were increased in 10 and 20 wt% of MAP compared with neat 4EP, due to the increasing intermolecular interaction between 4EP and MAP. And the decomposition activation energies ($E_{t}$) for thermal stability derived fromthe integral method of Horowitz-Metzger equation, were increased within the 10∼30 wt% composition range of MAP, resulting from increased crosslinking density in the blend system. The cross-linking activation energies ($E_{c}$) for rheological properties determined from the Arrhenius equation based on gel time and curing temperature, exhibited similar behavior to those of integral method which could be explained by the miscibility between 4EP and MAP.

The polyurethane prepolymer having diisocyanate end group was synthesized by poly addition reaction between hesamethylene diisocyanate (HDI, aliphatic type) or m-xylene diisocyanate (XDI, aromatic type) with ethylene glycol(EG). Prepolymer was characterized byFT-IR. Using this prepolymer, polyurethane microcapsules containing liquid (toluene, turpentine oil, pine perfume) as core material were prepared. The size and shape of microcapsule were observed by scanning electron microscope(SEM). The particle size distribution was analyzed by partile size analyzer. The spherical shape of capsule was more prevalent in XDI/EG system, compared with HDI/EG system. The size of microcapsule decreased with increasing emulsification speed and reaction temperature. The capsule prepared was attached to viscose fabric via PDC and printing method. The hand value of fabric was checked. The fabrics showed that Koshi value increased, while Numieri and Fukurami values were nearly same a untreated fabric.

Binding behavior of two cationic surfactants, dodecyltrimethylammonium bormide (DTAB) and tetradecyltrimethylammonium bromide(TTAB), to the chitosan-based polyelectrolyte was studied. Chitosan films used in this study were crosslinked with epichlorohydrin (ECH). Binding isotherms were determined by potentiometric technique using a surfactant ion selective solid-state electrode and the results are represented by using the sequence generating function(SGF) method. The results of binding isotherm indicated that there is comparatively low cooperativity. The effect of salts(NaCl, $MgCl_{2}$) n the binding isotherms was also studied. The addition of salts in the polyelectrolyte/surfactant system resulted in a shift of the binding to higher free surfactant concentration because the polymer charge was screened by the counterion. The swelling ratio of the crosslinked chitosan was found to increase with increasing degree of deacetylation(DD) and with decreasing crosslink density of chitosan. A conformational phase transition of the crosslinked chitosan gels, as the binding with DTAB and TTAB proceeded, has been investigated.

In this work the effect of annealing temperature on the tensile, thermal, and dynamic mechanical properties of poly(p-dioxanone) monofilament were investigate. The tensile strength and tensile elongation at beak increased with annealing temperature at a fixed immersion time. At the in-vitro immersion time of 10 weeks, the tensile strength as zero for samples annealed below 6$0^{\circ}C$, but for the samples annealed above 7$0^{\circ}C$ th tensile strength of 35 MPa was obtained. The hat of fusion increased with annealing temperature. Three endothermic peaks (84$^{\circ}C$, 93$^{\circ}C$, and 106$^{\circ}C$) were observed for the control sample and the sample annealed at 5$0^{\circ}C$. The endothermic peak at 93$^{\circ}C$ disappeared at annealing temperature of above 6$0^{\circ}C$. In the case of the immersion time of longer than 6 weeks, all samples showed a single endothermic peak. The maximum endothermic peak of samples increased with the immersion time at a fixed annealing temperature. The maximum loss modulus at each in-vitro immersion time showed an increasing tendency as the annealing temperature increased.

It is important to detect the tension of yarn in the spinning process. Contact type tension detectors have been used for this purpose until now. However, the contact type tension detectors lead to the end breakages, changes in the properties of yarn and so on. In this study we tried to solve these problems by developing a non-contact tyep tension detector. We devised the system to convert the frequency of yarn to the tension of yarn and used the photo interrupter to measure the frequency of yarn.

In this study the dynamic characteristics of a separator attached to two-for-one twister by bolt jointing were investigate by using finite element and experimental methods. Though in general, the bolt jointing has been considered as rigid joint, the boundary region of a separator was modeled by using the beam element with axial load in this paper. In order to assure the acceptability of the result of finite element, the experimental modal analysis was executed by the impact method. As a result of comparison between the finite element and experimental methods, assurance of a proposed finite element model with the beam element at the boundary region was obtained. The conventional separator needs to be improved in terms of cost and manufacturing process. The cost reduction and manufacturing process improvement are very important from an international competition point of view. Then, the new separator structure was prosed to enhance these factors without variation of dynamic characteristic. Through the finite element method and experimental modal analysis, it was found that the new model was well acceptable.