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열처리 조건에 따른 폴리아크릴로니트릴 섬유의 형태 및 물성
방윤혁,조현혹 한국섬유공학회 1994 한국섬유공학회지 Vol.31 No.11
As-spun filament of copolyacrylonitrile(AN/MA=95/5w1%) has been prepared and subsequcntly stretched. The stretched filaments which contain moisture were shrunk freely by 5%~25% on heating in dry air at 130~17$0^{\circ}C$. The change of morphology and mechanical properties was examined by various techniques such as thermal mechanical analyzer(TMA), scanning electron microscopy(SEM). rheovibron and tension. After heat treatment, residual shrinkage of fiber decreased significantly with increasing shrinkage, while it was little affected by heat treatment temperature. Electron microscopy revealed that surfaces of acrylic fibers were grooved along the fiber axis. The grooves developed by the collapse of voids during the process of drying increased slightly with increasing shrinkage and heat treatment temperature. Maximum tan § peak became broader with increasing shrinkage. Consequently, enhancement in thermal dimensional stability and mechanical properties of fibers treated under these conditions(16$0^{\circ}C$$\times$10%) may be due to an optimum increase of dipole bonds between -CN groups.
셀룰로오스/N-methylmorpholine-N-oxide(NMMO)/$H_2O$계에서 제조된 재생 셀룰로오스 필름의 미세 구조
방윤혁,이기환 한국섬유공학회 1998 한국섬유공학회지 Vol.35 No.6
The properties of cellulosic fibers are highly dependant on the fine structure. In particular a better understanding of the fine structure is required for the development of new spinning method of regenerated cellulosic fibers at cellulose/N-methylmorpholine-N-oxide (NMMO)/$H_2O$ system. The regenerated cellulosic films were made from cellulose/NMMO/$H_2O$ solutions with the change of degree of polymerization, cellulose concentration (wt%) of solution, and NMMO concentration (wt%) in the coagulation bath respectively. The quantification of crystalline content of regenerated cellulosic films was carried out by resolution of wide angle X-ray scattering intensity distribution on the assumption that all peaks take the symmetrical Gaussian distribution from centered at its Bragg angle. X-ray scattering patterns resolved into individual integral intensities showed that polymorphic structure mixed cellulose II and III were obtained for coagulated cellulosic films. The degree of crystallinity and apparent crystalline size of regenerated cellulosic films depended on degree of polymerization, cellulose concentration of solution, and NMMO concentration in the coagulation bath. The diameter of microfibril decreased with the increase of NMMO concentration.
고강력 폴리아크릴로니트릴 섬유의 열처리에 의한 미세구조변화(II)
방윤혁,이천용,조현혹,Bang, Yun-Hyuk,Lee, Chun-Yong,Cho, Hyun-Hok 한국섬유공학회 1995 한국섬유공학회지 Vol.32 No.5
The properties of carbon fibers made fiom PAN are controlled by the heat treatment conditions. The length changes during heat treatment of high strenffh homo-PAN and co-PAN(acrylonitrile/acrylamide : 9812wt%) fibers in nitrogen atmosphere were measured by monitoring the elongation-shrinkage behavior under variable loading from 0.02 to 0.1g/d. A few structure parameters such as aromaticity index and crystalline orientation etc. were determined for the fibers heat-treated by linear heating to 27$0^{\circ}C$. The onset temperature of the chemical shrinkage during heat treatment coincided with the one of the exothermic peak of DSC thermoyams. When PAN fibers are heated under variable loads, the fiber length changes by various ways, namely physcial shrinkage, balance-elongation and chemical shrinkage. The co-PAN fibers tend to shrink more readily than homo-PAN fibers in that the onset of chemical shrinkage of co-PAN is shified to lower temperature. The total shrinkage of PAN fibers decreased with increasing load.
고강력 폴리아크릴로니트릴 섬유의 열처리에 의한 미세구조 변화(IV)
방윤혁,이기환 한국섬유공학회 1995 한국섬유공학회지 Vol.32 No.9
The properties of carbon fibers made from PAN are controlled by precursor manufacture and heat treatment conditions. This work is concerned with the studies of morphological change of high molecular delight PAN film during heat treatment process with drawing conditions. The effect of heat treatment on the dynamic mechanical properties of PAN film was investigated in connection with the change of the mechanical loss tangent(tan) peak which may be attributed to cyclization procedure. The decrease of tan peak intensity was found to be related with the drawing condition. It is considered that the degree of the decrease of tn6 peak intensity may be due to the difference of chemical reaction and molecular motion in the amorphous region. The extent of morphological changes is also found to depend on the draw ratio. From a consideration of apparent activation energy of absorption(a2) and ammaticity index, it may be concluded that the structure of amorphous region is also a factor iuluencing the degree of cyclization.
방윤혁,이기환,조경래,왕영수,김한도,조현혹 한국섬유공학회 2000 한국섬유공학회지 Vol.37 No.12
This study describes the effect of bifunctional reactive dyestuffs treatment on the fibrillation control and fine structure of lyocell fiber having different spinning conditions. Reactive dyeing process with bifunctional dyestuffs reduced the extent of fibrillation on the surface of fiver due to crosslinking of cellulose chain molecules by means of hydrogen bridges or covalent bondings. The crosslinking reaction was found to increase in the order of the coagulated fiber > washed fiber > dry and heat treatment fiber manufactured in the spinning process. The extent of the reduction of fibrillation was decreased with draw ratio. The decrease of fibrillation in case of using R-2G is lower than in case of using FN-2R. Therefore, the crosslinking reaction was found to be closely related with the diffusion of dyestuff, due to the fine structure of the fiber and the chemical structure of the dyestuff.
방윤혁,왕영수,김한도,김덕리,조현혹 한국섬유공학회 2000 한국섬유공학회지 Vol.37 No.5
The relationship between the fibrillation and swelling of lyocell fibers(spun by N-metyl-morpholine N-oxide systems) was studied by varying the spinning conditions such as degree of polymerization($DP_{w}$), cellulose concentration, and draft ratio. The fibers, treated by constant stirring with stainless balls in the wet and dry state, exhibited a increase in the fibrillation index with increase in $DP_{w}$, cellulose concentration, and draft ratio. The decrease in wide angle X-ray scattering intensity with water swelling suggests that the less-ordered cellulose in and between the crystals take up water. The increase in fibrillation index correlates I inverse proportion to swelling.
Poly(ethylene terephthalate)(PET)(p-hydroxybenzonate(PHB) 열방성 액정섬유의 열처리
방윤혁,이기환,박종범,조현혹 한국섬유공학회 1999 한국섬유공학회지 Vol.36 No.9
The crystal lattice structure, thermal behavior, molecular orientation, and mechanical property of spun strands of a thermotropic liquid crystalline polymer (LCP) were studied with wide angle X-ray diffraction, differential scanning calorimetry, birefringence, and tensile tests. The purpose of this work is to elucidate the effects of draw-down ratio and annealing conditions on the structural development in the LCP strands. Relaxation of the lateral packing of PHB molecular chain in a copolymer of p-hydroxibenzoic acid and ethylene terephtalate (60/40) mole%) occurred in the course of annealing treatment. The annealing treatment slightly increased the crystalline orientation factor, whereas total molecular orientation was decreased by annealing. In addition, the relationship between initial modulus and annealing treatment was sensitive to total molecular orientation. The initial modulus increased with increase in the draw-down rate. The endothermic behavior at about 20$0^{\circ}C$ is due to the PET regions with the incorporation of PHB segments causing a diluent effect.