• Composites Research
• /
• v.33 no.2
• /
• pp.39-43
• /
• 2020

Recently, fabrication process of thermoplastic polyamide-based composites with recyclability as well as impact, chemical, and abrasion resistance have been widely studied. In particular, thermoplastic reactive resin transfer molding (TRTM) in which monomer with low viscosity is injected and in-situ polymerized inside mold has received a great attention, because thermoplastic melts are hard to impregnate fiber preform due to their very high viscosity. However, it is difficult to optimize the processing conditions because of high reactivity and sensitivity to external environments of the used monomer, ε-caprolactam. In this study, viscosity as an important process parameter in TRTM was measured during in-situ anionic polymerization of ε-caprolactam and the solutions for problems caused by high polymerization rate and sensitivity to moisture and oxygen were suggested. Reliability of the improved measurement technique was verified by comparing the viscosity behavior at various environmental conditions including humidity and atmosphere, and it is expected to be helpful for optimization of TRTM process.

• The KSFM Journal of Fluid Machinery
• /
• v.14 no.1
• /
• pp.42-47
• /
• 2011

Measurement uncertainty analysis of fuel flow using turbine flowmeter was performed for the case of altitude engine test. SAE ARP4990 was used as the fuel flow calculation procedure, as well as the mathematical model for the measurement uncertainty assessment. The assessment was performed using Sensitivity Coefficient Method. 11 parameters involved in the calculation of the flow rate were considered. For the given equipment setup, the measurement uncertainty of fuel flow was assessed in the range of 1.19~1.86 % for high flow rate case, and 1.47~3.31 % for low flow rate case. Fluctuation in frequency signal from the flowmeter had the largest influence on the fuel flow measurement uncertainty for most cases. Fuel temperature measurement had the largest for the case of low temperature and low flow rate. Calibration of K-factor and the interpolation of the calibration data also had large influence, especially for the case of very low temperature. Reference temperature, at which the reference viscosity of the sample fuel was measured, had relatively small contribution, but it became larger when the operating fuel temperature was far from reference temperature. Measurement of reference density had small contribution on the flow rate uncertainty. Fuel pressure and atmospheric pressure measurement had virtually no contribution on the flow rate uncertainty.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.337-337
• /
• 2002

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• v.11 no.2
• /
• pp.406-413
• /
• 2006

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.468-469
• /
• 2013

• Polymer(Korea)
• /
• v.35 no.1
• /
• pp.23-29
• /
• 2011

We measured shear viscosity of polymeric particles, prepared by suspension polymerization with hydrophobic silica as a stabilizer at $75^{\circ}C$, by a capillary rheometer. Shear viscosity displayed a non-Newtonian behavior with an increase in weight average molecular weight. Measurement of shear viscosity at 170 and $190^{\circ}C$ with copoly(styrene/butyl methacrylate) (co-PSB) particles by varying the ratio between styrene (St) and butyl methacrylate (BMA) showed that shear viscosity was a function of molecular weight, temperature and compositional ratio. When the ratio was 7/3, 5/5 and 3/7, shear viscosity slightly reduced with an increase in BMA concentration despite similar weight average molecular weights. We found that shear viscosity of copolymers with BMA concentrations exceeding 70% displayed a sharp reduction at high shear rates. It is speculated that increased PBMA chain length contributes to enhanced flowability of copolymers. When carbon black was incorporated into co-PSB, shear viscosity progressively increased with increasing carbon black concentration. The increase in shear viscosity, however, was less pronounced compared to the cases of molecular weight increase.

• Journal of the Korean Applied Science and Technology
• /
• v.34 no.1
• /
• pp.83-90
• /
• 2017

The polyurethane resin used for the garment skin leather surface coating was synthesized by varying the content of polyethylene glycol (PEG) in [NCO] / [OH] mole % ratio. The mechanical properties of the synthesized polyurethane resin were analyzed by SEM, FT-IR, UTM. As the [NCO] / [OH] mole % ratio of nonionic poly ethylene glycol (PEG) increased, there was no change in flexural resistance (dry, wet) and abrasion resistance and tensile strength measurement value were lowered. In contrast, the elongation property values were increased. The result of viscosity measurement showed that the viscosity became thinner with increasing [NCO] / [OH] mole % of PEG.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.12
• /
• pp.1699-1707
• /
• 2003

Coriolis mass flowmeter(CMF), which can measure the mass flow directly, is getting rapid attention for the industrial and custody transfer purpose. In order to study the characteristics and the applicability of CMF, it is tested with the national flow standard system. Two types of sensing tube, U-type and straight type, are employed in the test. Water, spindle oil and viscosity Standard Reference Material whose viscosities are 1, 20 and, 67 $\textrm{mm}^2$/s, respectively, are studied. It is shown that the linearity of CMF is getting deteriorated as the fluid viscosity increases, which is due to the zero drift and the relaxation time of the fluid. To test its applicability in the case of high pressured gas, it is calibrated using compressed air, It shows 1∼l.6 % deviations compared to the calibration results using water. It concludes that the fluid velocity in CMF should be lower than the sonic velocity. In addition, the effects of the vibration from the pipeline and pump on CMF as well as the long term stability are studied.

• Korean Journal of Food Science and Technology
• /
• v.20 no.2
• /
• pp.148-156
• /
• 1988

A method for the measurement of viscoelastic properties of heat denatured gluten network was developed in order to evaluate the noodle making quality of wheat flour. The stress relaxation of elongated heat denatured gluten network could be expressed by 6-element generallized Maxwell model. The tensile force of heat denatured gluten network increased by the heating time. The elastcity and viscosity of the first exponential term which covers 70-74% of the total relaxation increased as cooking time was extended up to 1q min. The addition of gluten network strengthening agent, potassium bromate, at 1000ppm level reduced the elasticity and viscosity, while weakening agent, L-cystein, increased them. The relaxation time decreased after 11 min of cooking in both cases. The elasticity and viscosity of heat denatured gluten were affected differently by the concentration of added urea.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.525-526
• /
• 2006

The products designed by human sensibility and ergonomics are given good impression. Especially the touch feeling on the human skin is very useful sensibility for quality of products. Elasticity and viscosity of human skin is very important element in product design based on ergonomics. In this paper, we describe a sophisticated method for measurement of dynamic viscoelasticity characteristics of human skin. For this measurement, we developed a measurement system assembled with load cell, actuator, amplifier and data acquisition system. The $MATLAB^{TM}$ is used to analyze the data and fit a approximation curves.