Kwok-wing Yeung

Moisture Management Tester: A Method to Characterize Fabric Liquid Moisture Management Properties

Fabric liquid moisture transport properties in multidimensions, called moisture management properties, significantly influence human perceptions of moisture sensations. A new method and instrument called the moisture management tester (MMT) is developed to evaluate textile moisture management properties. This new method can be used to quantitatively measure liquid moisture transfer in one step in a fabric in multidirections, where liquid moisture spreads on both surfaces of the fabric and transfers from one surface to the opposite. Ten indexes are introduced to characterize the liquid moisture management properties of fabrics. Eight sets of sportswear are tested with the MMT and the results show that liquid moisture management properties are significantly different for these fabrics. The objective measurements are compared with subjective perceptions of moisture sensations during exercise. A fabric’s one-way-transport capacity and its overall moisture management capacity are significantly correlated with perceptions of clammy and damp sensations with increased exercise time, indicating that subjective perceptions of moisture sensations in sweating such as clammy and damp can be predicted by the measurements of the MMT.

Development of shape memory polyurethane fiber with complete shape recoverability

To illustrate the shape memory properties of shape memory polyurethane (SMPU) fiber and the difference of thermal/mechanical properties between SMPU fiber and other various man-made fibers, series of shape memory polyurethane having various hard segment content were synthesized with the pre-polymerization method and spun with the wet spinning process. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical testing were conducted to study the particular thermal/mechanical properties of shape memory polyurethane fiber in comparison with other man-made fibers such as nylon6, polyester, Lycra and XLA. In addition, in the preparation of shape memory polyurethane fiber, the effect of thermal setting temperature was systematically investigated by mechanical properties testing, DMA and cyclic tensile testing, suggesting that the thermal setting temperature has a huge influence on the mechanical properties and shape memory property due to the elimination of internal stress. Thermal setting with a higher temperature will give rise to a lower tensile modulus and tenacity and a higher elongation ratio at break. Through employing the optimal thermal setting treatment, the complete heating responsive recovery in SMPU fiber can be achieved because of the counteracting effect of the irreversible strain and thermal shrinkage.

SHAPE MEMORY EFFECT OF PU IONOMERS WITH IONIC GROUPS ON HARD-SEGMENTS

SMPU (shape memory polyurethane) non-ionomers and ionomers, synthesized with poly(e-caprolactone) (PCL), 4, 4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), dimethylolpropionic acid (DMPA) were measured with cyclic tensile test and strain recovery test. The relations between the structure and shape memory effect of these two series were studied with respect to the ionic group content and the effect of neutralization. The resulting data indicate that, with the introduction of asymmetrical extender, the stress at 100% elongation is decreased for PU non-ionomer and ionomer series, especially lowered sharply for non-ionomer series; the fixation ratio of ionomer series is not affected obviously by the ionic group content; the total recovery ratio of ionomer series is decreased greatly. After sufficient relaxation time for samples stretched beforehand, the switching temperature is raised slightly, whereas the recovery ratio measured with strain recovery test method is lowered with increased DMPA con...

Effect of steaming on shape memory polyurethane fibers with various hard segment contents

To illustrate the effect of post-treatment high-pressure steaming and hard segment content on shape memory polyurethane (SMPU) fiber, a series of shape memory polyurethane having various hard segment contents was synthesized with the pre-polymerization method, spun with a wet spinning process and treated with high pressure saturated water vapor. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle x-ray diffraction (WAXD), mechanical testing and cyclic tensile testing were conducted to investigate the particular thermal/mechanical properties, crystallization of hard segments and shape memory properties of SMPU fibers. In addition, in the light of a comparison between the original and the treated SMPU fiber, the effect of steaming post-treatment in SMPU fibers with various hard segment contents was illustrated. The steaming treatment gives rise to a higher elongation ratio at break, lower tenacity and initial modulus. Hard segment crystallization can be induced, especially in fiber with higher hard segment content after treatment. The glass transition temperature of the soft segment of SMPU fibers was decreased after steaming and the trends are most likely significant in high hard segment content specimens. Steaming with high pressure saturated water vapor can eliminate the thermal shrinkage and provide dimensional stability to the original SMPU fibers. The recoverability remains well in all treated specimens, but the fixity ability decreases with the decrease of hard segment content.

Detecting Defects in Textile Products Based on Band-pass Filtering Techniques

Two dimensional band-pass filters can be used to enhance the edges of the defects contained in fabric images. In this paper, we designed two types of 2D band-pass filters for the automatic detection of defects. One is the matched Gabor filter, and the other is the matched Mexican hat wavelet. Experiments show that the matched Gabor filter is more suitable for defects of higher frequency, while the matched Mexican hat wavelet is more effective for defects of lower frequency. Based on the two types of band-pass filters, an automatic fabric defect detection system was designed which boasts good accuracy and high speed.