Chi-wai Kan

Surface properties of low-temperature plasma treated wool fabrics

Abstract Induced surface properties of wool fabrics created by the sputtering of low-temperature plasma treatment, such as surface lustre, wettability, surface electrostatic and dyeability, have been investigated. After the low-temperature plasma treatment, the treated wool fabric specimens exhibited better hydrophilicity and surface electrostatic properties at room temperature, together with improved dyeing rate. Study of the surfaces of the specimens showed that low-temperature plasma treatment did not effect any changes in the glossiness of the specimen. Scanning electron microscope observation illustrated the occurrence of some grooves on the fibre specimens that might possibly provide a pathway for a faster dyeing rate.

Using atmospheric pressure plasma treatment for treating grey cotton fabric.

Conventional wet treatment, desizing, scouring and bleaching, for grey cotton fabric involves the use of high water, chemical and energy consumption which may not be considered as a clean process. This study aims to investigate the efficiency of the atmospheric pressure plasma (APP) treatment on treating grey cotton fabric when compared with the conventional wet treatment. Grey cotton fabrics were treated with different combinations of plasma parameters with helium and oxygen gases and also through conventional desizing, scouring and bleaching processes in order to obtain comparable results. The results obtained from wicking and water drop tests showed that wettability of grey cotton fabrics was greatly improved after plasma treatment and yielded better results than conventional desizing and scouring. The weight reduction of plasma treated grey cotton fabrics revealed that plasma treatment can help remove sizing materials and impurities. Chemical and morphological changes in plasma treated samples were analysed by FTIR and SEM, respectively. Finally, dyeability of the plasma treated and conventional wet treated grey cotton fabrics was compared and the results showed that similar dyeing results were obtained. This can prove that plasma treatment would be another choice for treating grey cotton fabrics.

Assessing and predicting the subjective wetness sensation of textiles: subjective and objective evaluation:

Wetness sensation is a crucial factor affecting wear comfort. In this study, a measurement method that is capable of characterizing the subjective wetness sensation of various textile products, such as sportswear, leisurewear, uniforms and health-care products, was developed. A subjective rating scale was adopted for response measurement and 20 different fabrics varying in fiber composition, yarn type and fabric structure were evaluated by 22 subjects. The testing procedure was standardized, ensuring within-subject reliability and between-subject consistency. This method also displays high sensitivity and the result is rational with barely to slightly wet sensation for the absorbing fabrics and very wet feeling for the hydrophobic ones. In addition, an objective measurement method for evaluating the horizontal wicking area of fabrics utilizing the image analysis technique was developed. Using conventional testing instruments, such as the Gravimetric Absorbency Testing System, Moisture Management Tester, international standard testing methods and the proposed horizontal wicking tester, various objective water absorption and transport properties were measured and their correlation with the subjective wetness rating was studied. Horizontal wicking area and water absorption capacity of fabrics were found to have strong correlation with subjective wetness sensation.

Evaluating antistatic performance of plasma-treated polyester

Use of low temperature plasma treatment has been attempted in the textile industry and there the has been some success in the dyeing and finishing processes. In this paper, an attempt was made to apply low temperature plasma treatment to improve the antistatic property of polyester fabric. The polyester fabrics were treated under different conditions with low temperature plasma. An orthogonal array testing strategy was employed for obtaining the optimum treatment condition. After low temperature plasma treatment, the polyester fabrics were evaluated with different characterization methods. Under the observation of scanning electron microscope, the surface structure of the polyester fabric treated by low temperature plasma was found to be seriously altered which provided more capacity for polyester to capture moisture and hence increased the static charges dissipation. The relationship between moisture content and half-life decay time for static charges was studied and the results showed that the increase in moisture content would result in shortening of the time for static charges dissipation. Moreover, the antistatic property of the low temperature plasma treated polyester fabric was greatly improved. In addition, the antistatic property of the polyester fabric treated by low temperature plasma was compared with that of the polyester fabric treated with a commercial antistatic finishing agent.

Enhancing the capacitive performance of a textile-based CNT supercapacitor

A metal layer, used as a current collector layer for a textile-based supercapacitor (SC), was prepared on polyethylene terephthalate (PET) fabrics using wet chemical methods. By integrating this additional current collector layer into the SC structure, the carbon-nanotube (CNT)-based SC showed an improved capacitive performance. The specific capacitances of the CNT/Cu/PET SC and CNT/Au/PET SC were 4.312 × 10−3 F cm−2 and 3.683 × 10−3 F cm−2 respectively, about 60 times larger than that obtained from the CNT/PET SC without the metal collector layer. On the other hand, the energy densities of these CNT-based SCs with metal layers were found to be ∼50 fold increased as compared to the CNT/PET SC. Similarly, the power densities of these two SCs with current collector layers were two orders of magnitude larger than that of CNT/PET SC. High flexibility was also demonstrated in these two metal-layered SCs. For the durability measurement, the CNT/Au/PET SC showed a stable performance, with its specific capacitance maintained at about 89% of its initial value after 2500 charge–discharge cycles. However, the CNT/Cu/PET SC only showed a relatively short-term stability, as its specific capacitance dropped to 12% of its initial value after 2500 charge–discharge cycles. In order to further improve its capacitive performance, polyaniline (PANI) was deposited on the CNT/Au/PET SC surface using a cyclic voltammetric deposition method. A specific capacitance of 0.103 F cm−2, about 30 times larger than that of the CNT/Au/PET SC, was obtained in the PANI/CNT/Au/PET SC which also showed good flexibility as well as high stability performance, with only 11% drop after 2500 charge–discharge cycles. On the basis of our results, we believe that by integrating a thin current collector layer into the textile-based CNT SC, its specific capacitance is enhanced while its flexibility and durability can be maintained. This method allows us to make any non-conducting fabric into a SC and turn it into a portable and wearable energy storage device.

Plasma-assisted regenerable chitosan antimicrobial finishing for cotton

Abstract In this study, nitrogen-plasma treatment was used to enhance the coating of chitosan onto cotton fabric and chlorine was introduced into nitrogen-containing groups on the chitosan coated fabric in order to make it antimicrobial by chlorination with sodium hypochlorite. The antimicrobial property and its rechargeability were investigated. FTIR, UV and scanning electron microscope were used to evaluate the surface properties, including the existence of chitosan on cotton fabric, the content of chitosan on cotton fabric and the surface topography of cotton fabric after modification. The results showed that nitrogen-plasma introduces nitrogen-containing groups into cotton fabric, the coating of chitosan on fabric was improved with nitrogen plasma treatment and chlorine was introduced into the chitosan coated fabric successfully which inhibits bacteria effectively and it is rechargeable. Thus, the antimicrobial property of cotton fabric coated with chitosan with the aid of nitrogen-plasma treatment after chlorination achieved good effects.

Effects of TiO2 and curing temperatures on flame retardant finishing of cotton

The performance of flame retardancy of cotton cellulose can be influenced by curing conditions. In this study, cotton cellulose was imparted durable flame retardant properties by a reaction between a flame retardant agent (Pyrovatex CP New) and a cross linking agent (Knittex CHN), in the presence of catalysts phosphoric acid and titanium dioxide (TiO2). After treating cotton fabrics at different curing temperatures for different curing time, its flame retardant performance was evaluated by 45° fabric flammability standard test method. For cotton fabrics cured at 150 and 170°C, good flame retardant characteristics were retained even after three home laundering cycles. The use of TiO2 as a co-catalyst in the treatment improved the flame retardant properties and reduced the loss of tearing strength of cotton fabrics. No significant negative effect in the whiteness index was observed, as compared with conventional flame retardant treatment.

Influence of knitted fabric construction on the ultraviolet protection factor of greige and bleached cotton fabrics

The alarming increase of incidence of skin cancer has hastened development of ultraviolet (UV) protective clothing and research on UV protection of apparel. Although various fabric parameters that affect ultraviolet radiation (UVR) transmission were studied by researches, most of them focused on woven fabrics and chemical approach in enhancing UV protection. There were few studies concerning knitted fabrics, in particular the influence of fabric constructions on ultraviolet protection factor (UPF) and structural properties. The magnitude of transmission and scattering of UVR through a fabric is decided by fabric construction or knit structure, which is classified by geometrical arrangement of yarns and fibers of the fabric. This paper aimed at studying the influence of different knit structures upon the UPF with the three main knit stitches incorporated in the knitted fabric constructions, namely the knit, tuck and miss stitches. The UPF and structural characteristics, including thickness, weight, stitch density and porosity of greige and bleached knitted fabrics with different knit structures, are compared by adopting factorial analysis of variance. The results show that fabrics with miss stitches possess a higher UPF than fabrics with tuck stitches. The double-knitted fabrics have better UV protection than the single-knitted fabrics overall, but bleaching has different impacts on the UPF of single- and double-knitted fabrics. The study reveals that fabric thickness or weight cannot be used solely in explaining the UV protective performance of knitted fabrics. However, fabric porosity can be a good indicator for UV protection when comparing fabrics with similar fabric weight and thickness but different structures or fiber contents.

Characterizing the transplanar and in-plane water transport properties of fabrics under different sweat rate: Forced Flow Water Transport Tester

The water absorption and transport properties of fabrics are critical to wear comfort, especially for sportswear and protective clothing. A new testing apparatus, namely Forced Flow Water Transport Tester (FFWTT), was developed for characterizing the transplanar and in-plane wicking properties of fabrics based on gravimetric and image analysis technique. The uniqueness of this instrument is that the rate of water supply is adjustable to simulate varying sweat rates with reference to the specific end-use conditions ranging from sitting, walking, running to other strenuous activities. This instrument is versatile in terms of the types of fabrics that can be tested. Twenty four types of fabrics with varying constructions and surface finishes were tested. The results showed that FFWTT was highly sensitive and reproducible in differentiating these fabrics and it suggests that water absorption and transport properties of fabrics are sweat rate-dependent. Additionally, two graphic methods were proposed to map the direction of liquid transport and its relation to skin wetness, which provides easy and direct comparison among different fabrics. Correlation analysis showed that FFWTT results have strong correlation with subjective wetness sensation, implying validity and usefulness of the instrument.

Effect of softener and wetting agent on improving the flammability, comfort, and mechanical properties of flame-retardant finished cotton fabric

Cotton, a commonly used textile material, tends to burn easily. For some specific end-uses, flame-retardant (FR) properties are required. However, this kind of finish tends to worsen the hand feel and strength of the fabric. This study explored the feasibility of applying softener and wetting agent during flame-retardant treatment of cotton fabrics to improve their comfort and mechanical properties. Here, flame-retardant agent Pyrovatex CP New, crosslinking agent Knittex CHN, and phosphoric acid were combined with various softeners and wetting agent, and applied to the fabrics using a pad–dry–cure process. Fabric combustibility was evaluated by 45° flammability test. The thermal decomposition behavior and chemical structure of the samples were characterized by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The thermophysiological comfort properties, hand, and mechanical properties of the fabrics were additionally measured. The results demonstrated that FR-treated cotton specimens had lower strength and poor fabric hand and wettability, which might be caused by formation of crosslinks due to the acidic reaction condition and high curing temperature. Meanwhile, softener addition could compensate for these drawbacks and remarkably improve fabric hand and strength. On the other hand, addition of wetting agents could improve the flame resistance of the FR-treated fabrics.