• Title, Summary, Keyword: Crystallinity

Search Result 1,972, Processing Time 0.054 seconds

Determination of crystallinity index of cellulose depending on sample preparation and analysis instruments (시료 조건 및 측정방법에 따른 셀룰로오스의 결정화도 평가)

  • Ahn, Jung-Eon;Youn, Hye-Jung;Joung, Yang-Jin;Kim, Tae-Young
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.44 no.4
    • /
    • pp.43-50
    • /
    • 2012
  • The crystallinity index is an important characteristic of cellulose. The crystallinity value is different depending on the adopted instrument. In this study, we determined a crystallinity index of cotton and wood celluloses using wide-angle X-ray scattering (WAXS), powder X-ray diffractometer (PXRD), and cross polarization/magic angle spinning solid-state $^{13}C$ nuclear magnetic resonance spectroscopy (CP/MAS solid-state $^{13}C$ NMR). The specimen was prepared in forms of powder, sheet and pallet. With the comparison of the obtained crystallinity indices of the cellulose, the effects of the analysis instrument, the sample preparation and analysis method were investigated. Among three instruments, the crystallinity indices by PXRD and NMR had a good relationship and reproducibility, and WAXS gave the crystallinity index with poor reproducibility. In the case of analysis methods of crystallinity indices, the Segal method showed higher value than that of the Ruland-Vonk method. We expect that this study would be applicable to evaluate the crystallinity index of various cellulose materials with accuracy and reproducibility.

Crystallinity of yellow colored silkworm variety cocoons

  • Park, Bo Kyung;Nho, Si Kab;Um, In Chul
    • International Journal of Industrial Entomology
    • /
    • v.38 no.2
    • /
    • pp.51-55
    • /
    • 2019
  • The structure and properties of silk polymers (fibroin and sericin) can be satisfactorily controlled by choosing a suitable silkworm variety and, hence, this parameter (i.e., silkworm variety) has attracted increasing attention. A previous study reported that the crystallinity of white colored silkworm cocoons depends on the silkworm variety. In the present study, sixteen yellow colored silkworm variety cocoons were produced and their molecular conformation and crystallinity were investigated. The conformation of the silkworm cocoons varied with the silkworm variety. Most cocoons exhibited ${\beta}$-sheet conformation, although random coil and ${\beta}$-sheet conformations co-existed in some cocoons (e.g., 21 and D90). The crystallinity of the silkworm cocoons varied with the silkworm variety and the measurement position of the cocoon (i.e., outer surface or inner surface). However, the difference in the crystallinity indices of the outer and inner surfaces comprising the cocoons varied with the silkworm variety, but was <2% for all cocoons, except for MAL.

effect of Heating Rate on the Mechanical Properties in the Crystallization of $Li_2O$.$2SiO_2$ Glass ($Li_2O$.$2SiO_2$유리의 결정화에서 승온속도가 기계적 특성에 미치는 영향)

  • 최병현;고경현;안재환;지응업
    • Journal of the Korean Ceramic Society
    • /
    • v.33 no.7
    • /
    • pp.809-815
    • /
    • 1996
  • When Li2O.2SiO2 glass was crystallized between the temperature of maximum nucleation and the temperature of maximum crystal growth it was found that the control of heating rate had serious effect on the crystallinity and microstructure and the greatly changed physical properties. Density and elastic modulus tends to increase but thermal expansion coefficient decreased with increased crystallinity. When heating rate between the tempe-rature of maximum nucleation and the temperature of maximum crystal growth was 10~5$0^{\circ}C$/hr. crystallinity was increased to result in the increment of strength. When nuclation was done at 44$0^{\circ}C$ for 5 hours and the temperature of crystal growth was held at 575$^{\circ}C$ strength was increased until crystallinity reached 65% and strength was decreased with higher crystallinity. These phenomena could be explained that even for the same crystallinity different heat rates resulted in different number and size of cracks.

  • PDF

Gamma-Irradiated Ultra-high Molecular Weight Polyethylene : Anisotropic Changes in Crystallinity and Crosslinking

  • Lee, Kwon-Yong
    • Journal of Biomedical Engineering Research
    • /
    • v.18 no.2
    • /
    • pp.107-112
    • /
    • 1997
  • The effect of gamma-irradiation sterilization on molecular structural changes in orthopaedic surgical-grade polyethylene was studied. The relative crystallinity ud. percent crosslinking of the substance increased as a result of the gamma irradiation and varied anisotropically as a function of depth. Samples from the articulating surfaces showed 5% Venter relative crystallinity than those from the mid-sections, whereas samples from the mid-sections exhibited 15% greater crosslinking than those from the surfaces. These anisotropic variations are discussed in assDciation with oxidation.

  • PDF

Solid Phase Crystallizations of Sputtered and Chemical Vapor Deposited Amorphous Hydrogenated Silicon (a-Si:H) Thin Film (스퍼터링 및 화학기상 증착 비정질 수소화 실리콘박막의 고상결정화)

  • 김형택
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.11 no.4
    • /
    • pp.255-260
    • /
    • 1998
  • Behavior of solid phase crystallizations (SPC) of RF sputtered and LPCVD amorphous hydrogenated silicon film were investigated. LPCVD films showed the higher degree of crystallinity and larger grain size than sputtered films. The applicable degree of crystallinity was also obtained from sputtered films. The deposition method of amorphous silicon film influenced the behavior of post annealing SPC. Observed degree of crystallinity of sputtered films strongly depended on the partial pressure of hydrogen in deposition. The higher deposition temperature of sputtering provided the better crystallinity after SPC. Due to the high degree of poly-crystallinity, the retardation of larger grain growth was observed on sputtering film.

  • PDF

Quantification of Crystallinity Change in Celluloses during Refining

  • Kim, Chul-Hwan;Yang, Jae-Kyung;Park, Jong-Yawl
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.32 no.5
    • /
    • pp.8-13
    • /
    • 2000
  • X-ray diffraction technique was used to quantify change of cellulose crystallinity during refining. XRD data confirmed that fiber wall delamination was caused by the structural conversion of celluloses which occurred in a liquid medium during refining. The quantified crystallinity of celluloses in pulp fibers was closely associated with the change of fiber wall delamination, which was defined by measurement of fiber wall thickness. In particular, it was well recognized that low intensity beating showed a better response in the change of crystallinity than high intensity one. The decrease o cellulose crystallinity during refining considerably enhanced the improvement of interfiber bonding ability of a dried sheet.

  • PDF

Molecular conformation and crystallinity of white colored silkworm cocoons with different silkworm varieties

  • Park, Bo Kyung;Nho, Si Kab;Um, In Chul
    • International Journal of Industrial Entomology
    • /
    • v.38 no.1
    • /
    • pp.18-23
    • /
    • 2019
  • Bombyx mori silkworm has many silkworm varieties and the structure and properties of silk can be varied depending on the silkworm variety. Therefore, the choice of proper silkworm variety can be an effective way to control and improve the performance of silk materials in biomedical and cosmetic applications. As a preliminary study, in the present study, thirty nine Bombyx mori silkworm cocoons were prepared and their molecular conformation and crystallinity were examined. Molecular conformation and the crystallinity of silkworm cocoons were different depending on the silkworm variety. Interestingly, the crystallinity index of outside of cocoon was different from that of inside of cocoon and the difference between the crystallinities of outside and inside of cocoon was varied depending on the silkworm variety. In this study, the silkworm variety cocoons were classified into three groups (Group 1, Group 2, and Group 3) based on the difference of crystallinities between outside and inside.

The Difference of the Degree of Crystallinity of Foamed Plastics Depending on the Pressure Gradient in Mold Cavity (금형 cavity 내의 압력 차이에 의한 발포사출품의 결정화도 차이)

  • 이동욱;차성운;현창훈
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.1354-1357
    • /
    • 2003
  • Mold Analysis is crucial factors in the design of injection molding process. Since the qualify of products depends on filing, shrinkage and etc, the procedure of prediction through analysis in the design of injection molding process is needed. In many cases, this kind of analysis makes it possible to predict pressure pattern which determines the condition of injection molding process. Crystallinity is the factor that determines the shrinkage of products. The studies showed the factors that had been related to the degree of crystallinity, which were mostly Weight Reduction, mold temperature and melt temperature. Therefore, the objective of this study is to see the differences of the degree of crystallinity depending on the positions of foamed plastics. The procedure of this study is as the following. First, Simulate the pressure gradient in mold cavity that can produces specimen by using Moldflow. Secondly, produce specimen and measure the degree or crystallinity of each part of specimen by using XRD. Lastly, identify the sensitivity of conventional plastic and foamed plastic on pressure gradient by comparing the simulation and the results of measurement.

  • PDF

Analysis of the effect of flow-induced crystallization on the stability of low-speed spinning using the linear stability method

  • Shin Dong Myeong;Lee Joo Sung;Jung Hyun Wook;Hyun Jae Chun
    • Korea-Australia Rheology Journal
    • /
    • v.17 no.2
    • /
    • pp.63-69
    • /
    • 2005
  • The stability of low-speed spinning process exhibiting spinline flow-induced crystallization (FIC) with no neck-like spinline deformation has been investigated using the method of linear stability analysis. Effects of various process conditions such as fluid viscoelasticity and the spinline cooling on the spinning stability have been found closely related to the development of the spinline crystallinity. It also has been found that the FIC makes the system less stable or more unstable than no FIC cases when the spinline crystallinity reaches its maximum possible value, whereas the FIC generally stabilizes the system if the crystallinity doesn't reach its maximum value on the spinline. It is believed that the destabilizing effect of the FIC on low-speed spinning when the crystallinity is fully developed on the spinline is due to the reduction of the real spinning length available for deformation on the spinline. On the other hand, the increased spinline tension caused by the FIC when the maximum crystallinity is not reached on the spinline and thus no reduction in the spinning length occurs, makes the sensitivity of spinline variables to external disturbances smaller and hence stabilizes the system. These linear stability results are consistent with the findings by nonlinear transient simulation, as first reported by Lee et al. (2005b).

Adsorption Characteristic of Endo I and Exo II Purified from Cellulase by Trichoderma viride on Celluloses with Different Crystallinity (결정성이 다른 셀룰로오스에 대한 Trichoderma viride속 Cellulase로부터 분리한 Endo I 및 II의 흡착특성)

  • 김동원;홍영관;장영훈;이재국
    • KSBB Journal
    • /
    • v.13 no.2
    • /
    • pp.162-167
    • /
    • 1998
  • The adsorption behaviors of two major cellulase components, endo I and exo II, from Trichoderma viride were investigated using $\alpha$-celluloses with different correlation crystallinity index(Cc) as substrates. The adsorption of cellulase enzyme components was significantly affected by the reaction condition and the physicochemical properties of the cellulose. The $\alpha$-cellulose was hydrolyzed in the presence of cellulase for various periods. The correlation crystallinity index of $\alpha$-cellulose increased with increasing the hydrolysis time. The adsorption was apparently found to obey the first-order kinetics, and the adsorption activation energy(Ea) was calculated from the adsorption rate constant(ka). The value of adsorption rate constant for endo I was larger than that of exo II. This means that endo I are adsorbed more rapidly than exo II. With the increase in correlation crystallinity index, the values of the adsorption rate constants for endo I and exo II decreased, respectively. The activation energy for the adsorption of exo II on the cellulose also was larger than that of endo I. Also adsorption activation energy of endo I and exo II increased with an increase in the crystallinity of sample cellulose.

  • PDF