Christopher Hurren

Characterization of Conductive Polypyrrole Coated Wool Yarns

Wool yarns were coated with conducting polypyrrole by chemical synthesis methods. Polymerization of pyrrole was carried out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical properties of the yarn upon coating with conductive polypyrrole are presented. Coating the wool yarns with conductive polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yarn. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yarn.

The effects of ultrasonic agitation in laundering on the properties of wool fabrics.

This paper investigates the use of ultrasonic agitation as a method for reducing felting and area shrinkage during the laundering of wool fabric. Work was conducted to evaluate the changes in fibre and fabric properties after repeated exposure to ultrasonic agitation, and also the effectiveness of ultrasonic treatment to remove common stains. Fabric colour, appearance, tensile strength, dimensional stability and thickness were measured before and after each test. Ultrasonic agitation produced fine cracks in the scale structure of the fibre, but these had negligible effects on the strength and colour when compared to hand washing. Ultrasonic agitation caused less fibre migration than hand washing, with a reduced rate of thickness increase and felting. Ultrasonic agitation increased the level of stain removed from the fabric when compared with hand washing.

The dimensional and mechanical properties of wool/polyester fabrics made from vortex and ring-spun yarns

Fabric woven from wool/polyester (PES) Murata vortex spun (MVS) blend yarn is a commercially viable proposition particularly on the basis of advantageous wear-resistant properties, compared with fabric made from traditional worsted ring-spun yarn. However, in some early industrial trials with fabric made from 45/55-blend wool/PES MVS yarn, significantly greater relaxation shrinkage was found relative to comparable worsted ring-spun fabric. It was noted at the time that the amount of relaxation shrinkage in MVS fabric could be reduced to a large extent by using steamed MVS yarn. In this study, the extent of variations in the dimensional and mechanical properties of fabric samples woven from a combination of steamed and unsteamed MVS yarn and equivalent worsted ring-spun yarn is examined. In general, greater hygral expansion and relaxation shrinkage were found in loom-state fabrics made from unsteamed MVS yarns, whereas the fabric made from steamed MVS and ring-spun yarns gave relatively low levels of relaxation shrinkage and hygral expansion. Permanent setting of fabrics, by pressure steaming, was found to be more effective than yarn pre-steaming in reducing relaxation shrinkage levels of fabrics made from unsteamed MVS yarn. After pressure steaming, all fabrics showed similar levels of relaxation shrinkage and hygral expansion. Permanent setting of the fabrics, by pressure steaming, resulted in similar levels of relaxation shrinkage and hygral expansion, irrespective of the yarn production method; relaxation shrinkage fell to around 1% and hygral expansion increased by about 1%, relative to the loom-state samples. MVS fabrics were relatively heavier and fuller and had a firmer handle than the worsted ring-spun fabrics, reflecting the greater fabric weight, thickness and shear rigidity measured on these fabrics. These attributes are associated with different structures of the worsted ring-spun and MVS yarns used to make the fabrics.

Comparative analysis of two selective bleaching methods on Alpaca fibers

Dark brown Alpaca fiber was reduced in shade via selective bleaching with peroxide. Two selective oxidative bleaching methods were tested on alpaca top to assess their effectiveness for color removal and fiber quality properties. Color change, bundle strength, weight loss, fiber diameter, surface modification, dye-ability and dye wash fastness were assessed for both methods and compared with the original brown top. Bleach method 1 (BL-I) showed little surface modification, 5.8 % weight loss and 2.4 % strength loss. D1925 yellowness index was reduced to 74.3 from 83.1 and provided a good base for the dyeing of medium to deep shades. Bleach method 2 (BL-II) displayed considerable surface modification, 7.8 % weight loss and 18 % strength loss. BL-II also resulted in a mean diameter reduction of 1.9 micron during bleaching. Yellow-ness was reduced to 64.5 from 83.1 and provided a very good base for the dyeing of medium to deep shades. BL-I showed better exhaustion of the pre-metallised dye Lanaset Violet B than BL-II. Wash fastness for BL-II was 1 grey scale unit poorer than BL-I. BL-II showed far better color clarity at pale depths however the wash fastness of the finished product was not good enough to maintain the depth or clarity of the color. BL-I showed poorer clarity of color but exhibited better wash fastness results.

Ultrasonic scouring of wool and its effects on fibre breakage during carding

Ultrasonics has shown the potential to reduce the cost and environmental impact of textile processing. This work investigates the impact of ultrasonic scouring on fibre entanglement caused during the scouring process. Levels of fibre entanglement were quantified by measuring fibre length using OFDA4000 after carding. A significant reduction in fibre entanglement after ultrasonic scouring was observed and this was due to a reduced fibre migration in the wash bath when compared with the mechanical agitation seen in conventional scouring process. Fibre cuticle scale damage resulting from the ultrasonic irradiation may also have contributed to the reduction in fibre entanglement. A reduced level of fibre entanglement from ultrasonic wool scouring leads to a reduction in fibre breakage during carding.

Frequency dependence of ultrasonic wool scouring

Conventional aqueous scouring of greasy wool promotes wool felting and can be energy and water intensive. Ultrasonic wool scouring could be an alternative technology to minimise the negative impact, provided that the cleaning efficiency and fibre quality are not compromised. This study examined the influence of ultrasonic irradiation frequency and ultrasonic power variations on wool scouring performance at different liquor ratios. Scoured fibre, residual ash content, residual grease content, whiteness and yellowness were evaluated. The impact of liquor degassing on wool scouring effectiveness was studied. Fibre surface damage was also assessed in this work. It was observed that while there was no significant influence of ultrasonic frequency on the whiteness or yellowness of the scoured fibres, wool scoured at frequencies of 28 kHz and 80 kHz had more grease and dirt removed than that scoured at 45 kHz. Low ultrasonic power and degassed bath liquor increased wool grease removal ability. Ultrasonic treatment caused scale cracking/peeling in some wool fibres. More severe cuticle damage was observed in fibres scoured at the lower frequency. This damage resulted in increased dye uptake by the fibres.

Thermal and Mechanical Properties of Ultrasonically Treated Wool

Wool fabrics, ultrasonically treated in various chemical conditions and for different time durations, were analysed for thermal properties by thermo-gravimetric analysis and differential scanning calorimeter, in comparison with the untreated fabric. Fabric mechanical properties, such as bending and tensile performance, and changes in fibre morphology were also evaluated before and after ultrasonic treatment. It is found that wool treated with ultrasonics at the appropriate time, has less mass loss and a higher thermal degradation temperature than that without ultrasonic treatment or with prolonged ultrasonic treatment. Resistance to thermal degradation is reduced when wool is ultrasonically treated in the presence of alkali. Differential scanning calorimeter analysis shows that while ultrasonic treatment has little effect on fibre crystallinity, an appropriate treatment can provide wool with increased water absorption. Ultrasonic treatment stiffens wool fabric to some extent when the treatment time is prolonged. The addition of detergent alone to the ultrasonic bath has little effect on fabric tensile behaviour, whereas a treatment with both detergent and alkali produces severe fibre damage and significant loss of fabric tensile strength.

Effects of laundering on conductivity of polypyrrole-coated textiles

This study examines the resistance change in conductive polypyrrole-coated PET fabrics under the AS 2001.4.15 – 1994 laundering test conditions. The effects of individual detergent components of a standard detergent, including auxiliary chemicals, at four different temperatures were studied. When the coated fabric was washed under the AS 2001.4.15-1994 conditions, the ECE reference detergent and pure soap flakes (sodium sterate) both decreased the conductivity of the coating at a rate exponentially proportional to the laundering temperature. Detergent types had an influence over the rate of degradation; pH conditions had a large influence on the rate of polymer deterioration with the acidic nonionic detergent giving rise to significantly improved laundering conditions. The auxiliary chemicals, sodium carbonate and sodium perborate were seen to cause large degradation of polymers during laundering. Ethylene diamine tetra acetic acid was seen to have only a slight influence on the reduction of conductivity of polymers.

Correlating the fineness and residual gum content of degummed hemp fibres

It is well known residual gum exists in degummed or retted hemp fibres. Gum removal results in improvement in fibre fineness and the properties of the resultant hemp yarns. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibres and the fibre fineness, described in terms of fibre width in this paper. This study examined the mean width and coefficient of variation (CV) of fibre width of seventeen chemically retted hemp samples with reference to residual gum content. The mean and CV of fibre width were obtained from an Optical fibre diameter analyser (OFDA 100). The linear regression analysis results show that the mean fibre width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fibre width and the residual gum content. The strong linear co-relation between the mean of fibre width and the residual gum content is a significant outcome, since testing for fibre width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fibre cross-section hence the term “fibre width” is used instead of fibre diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at 1370 cm−1, 1325 cm−1, 1733 cm−1, and 1600 cm−1 attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.

Bending and abrasion fatigue of common suture materials used in arthroscopic and open orthopedic surgery

In orthopedic surgery, the reattachment of tendon to bone requires suture materials that have stable and durable properties to allow time for healing at the tendon–bone interface. The suture, not rigidly restrained within the anchor eyelet, is free to move during surgery and potentially after surgery with limb motion. During such movement, the suture is subjected to bending and frictional forces that can lead to fatigue‐induced failure. We investigated some common contemporary commercial number‐two‐grade suture materials and evaluated their resistance to bending abrasion fatigue and the consequent failure. Sutures were oscillated over a stainless steel wire at low frequency under load. Number of abrasion cycles to failure, changes in suture morphology, and fatigue‐failure method was recorded for each material. Suture structure had a significant effect on abrasion resistance, with braided sutures containing large numbers of fine high tenacity core filaments performing15–20 times better than other braided suture structures. Ultra high molecular weight polyethylene (UHMWPE) core filaments resisted bending abrasion failure better than other core materials due to the load spreading and abrasion resistance of these filaments. Sutures with UHMWPE cores also had high resistance to tensile failure. Limited correlation was observed between tensile strength and abrasion resistance.