Recent developments in wool related research in Australia

Fibre related research in Australia is entering a new era. In May 2010, the former Prime Minister of Australia, Mr Kevin Rudd, announced a $37 million grant under the Education investment Fund (EIF) scheme to establish the Australian Future Fibres Research and Innovation Centre (AFFRIC) at Deakin University’s Geelong Campus. This is $102 million joint initiative between Deakin University, CSIRO Materials Science and Engineering (MSE) and the Victorian Centre for Advanced Materials Manufacturing (VCAMM). Wool related research fits within two of the four program areas under AFFRIC: green natural fibres and functional fibrous materials. Selected examples of our recent wool related research are discussed, with a focus on the work involving researchers at Deakin University.

A correlation study of subjective sensorial evaluation and objective softness measurement of wool fabrics

Comfort is one of the most important aspects of clothing, especially for next-to-skin garments such as shirts and trousers for summer. Sensorial comfort has a strong relationship with both the mechanical and surface properties of apparel fabric. A comfortable textile material should have properties of softness, smooth surface or texture, be pleasant to touch and very flexible. When assessing fabric handle subjectively, the assessor usually strokes the fabric surface with one or several fingers and squash the fabric gently in hand. Thus, the perception of such handle includes complex parameters of compression, tactile sensation and textural effect. In this work, we attempted to use a simple technique of objectively evaluating fabric softness related properties, by measuring the force required to pull a fabric strip through a series of parallel pins (the pulling force). We also subjectively rated the fabric handle. The correlation analysis showed very good agreement between the fabric pulling force and subjective hand rating.

The effect of humidity and temperature on Wool Comfort Meter assessment of single jersey wool fabrics

The Wool ComfortMeter provides an objective measurement of the fabric-evoked prickle discomfort rating provided by wearers. This work aimed to quantify the sensitivity of the Wool ComfortMeter over a range of different temperature and humidity conditions to determine the recommended test conditions for its operation. The design was: three temperatures (notionally 20, 25 and 30°C) at three relative humidities (RHs, notionally 50, 65 and 80%) each with two replicates, using six different wool single jersey knits (mean fibre diameter 19.5–27.0 µm). As it was difficult to achieve exactly some of the extreme combinations of temperature and RH, some combinations were repeated, providing a total of 23 different assessment conditions. Data were analysed using restricted maximum likelihood mixed model analysis. The best fixed model included RH, RH2, temperature and the interaction of temperature and RH, accounting for 95% of the variation in Wool ComfortMeter readings. Wool ComfortMeter values were almost constant at 55–60% RH. Generally, the Wool ComfortMeter value reduced with increasing RH > 60% at temperatures of 25°C and 28.5°C as the regain of the fabric increased. However, at 20°C little change was detected as RH was increased from 50 to 80% as there were only small changes in fabric regain. The observed effects were in a good agreement with existing knowledge on the effect of regain on the mechanical properties of wool fibre. Wool ComfortMeter is best operated under standard conditions for textile testing of 65% RH and 20°C.

Effect of surface treatment and knit structure on comfort properties of wool fabrics

The comfort properties of the pique and single jersey knitted wool fabrics were investigated using the Wool ComfortMeter (WCM). The fabrics were knitted in three cover factors and treated with either plasma or a silicone softening agent and were compared with untreated fabrics. Plasma treatment did not show significant effects on the comfort value. However, silicone polymer significantly reduced WCM values suggesting that the silicone coating reduced the number of protruding fibres on the fabric surface. Regardless of treatment used, pique fabrics showed a lower WCM value, and therefore were perceived to be more comfortable than the single jersey structure. While the effect of cover factor was not significant, in fitted model to predict the WCM value of fabrics, mass/unit area and fabric thickness were significant predictors along with fabric structure and finishing treatment.

Photostability of wool fabrics coated with pure and modified TiO2 colloids

The surface of wool fabrics was coated with TiO2 and TiO2-based nanocomposite colloids and the impact of this coating on the photostability of wool was investigated. TiO2 along with TiO2/Metal and TiO2/Metal/SiO2 sols were synthesized through a low-temperature sol-gel method and applied to fabrics. Composite colloids were synthesized through integrating the silica and three noble metals of silver (Ag), gold (Au) and platinum (Pt) into the synthesis process of sols. Four different molar ratios of Metal to TiO2 (0.01%, 0.1%, 0.5% and 1%) were used to elucidate the role of metal type and amount on the obtained features. Photostability and UV protection features of fabrics were evaluated through measuring the photo-induced chemiluminescence (PICL), photoyellowing rate and ultraviolet protection factor (UPF) of fabrics. PICL and photoyellowing tests were carried out under UVA and UVC light sources, respectively. PICL profiles demonstrated that the presence of pure and modified TiO2 nanoparticles on fabrics reduced the intensity of PICL peak indicating a lower amount of polymer free radicals in coated wool, compared to that of pristine fabric. Moreover, a higher PICL peak intensity as well as photoyellowing rate was observed on fabrics coated with modified colloids in comparison with pure TiO2. The surface morphology of fabrics was further characterized using FESEM images.

Reducing photoyellowing of wool fabrics with silica coated ZnO nanoparticles

Though ZnO nanoparticles (NPs) are an excellent UV absorber, their photocatalytic activity greatly limits the application areas of these particles. Under sunlight exposure, ZnO NPs used as a UV absorber can accelerate the wool yellowing process by generating free radicals. To reduce this photocatalysis effect, a physical barrier has been fabricated by coating the ZnO NPs with a silica layer (ZnO@SiO2), hence providing good UV-shielding with low photocatalytic activity. The structure and optical properties of ZnO and ZnO@SiO2 NPs were characterized by transmission electron microscope (TEM) and UV–Vis spectrum. The photocatalytic activity of ZnO and ZnO@SiO2 NPs was evaluated by photo-degradation of Rhodamine B. The ZnO and ZnO@SiO2 NPs were applied to knitted wool fabrics using the dip coating method. The treated wool fabrics were characterized by a scanning electron microscope (SEM) and the photoyellowing level of treated fabrics after exposure under simulated sunlight was evaluated by a Datacolor Spectraflash spectrophotometer. The ZnO@SiO2 NPs demonstrated excellent protection of wool against photoyellowing.

Relationships between wearer assessment and the instrumental measurement of the handle and prickle of knitted wool fabrics

The relationships between wearer-assessed comfort and objectively measured comfort and handle parameters were investigated using 19 pure wool single jersey garments made of single ply yarns. Wearer trials were used to determine prickle discomfort, and whether wearers “liked” the garments. Fabrics then were objectively evaluated using the Wool HandleMeter, which measures seven primary handle attributes; and the Wool ComfortMeter (WCM), to predict a wearer's perception of fabric-evoked prickle. Wearer responses and the relationships within and between objective measurements and the effect of fibre, yarn and fabrics attributes were analysed by general linear modelling. Mean fibre diameter, fibre diameter coefficient of variation, yarn count, fabric thickness, fabric density, fabric mass per unit area and decatising affected one or more handle parameters. The best model for predicting wearer prickle discomfort accounted for 90.9% of the variance and included only terms for the WCM and WCM2. The WCM was a good predictor whereas mean fibre diameter was a poor predictor of whether wearers “liked” garments. Wearer assessment of prickle and whether or not wearers “liked” fabrics were independent of fabric handle assessment. The results indicate that the handle and comfort properties of lightweight, wool jersey fabrics can be quantified accurately using the Wool HandleMeter and the Wool ComfortMeter. For fabric handle, fibre and yarn characteristics were less important than changes in the properties of the fabric.

Fabric handle properties of superfine wool fabrics with different fibre curvature, cashmere content and knitting tightness

The handle properties of single jersey fabrics composed of superfine wools (17 μm) of different fibre curvature (114 vs. 74 °/mm) in blends with cashmere (fibre curvature 49 °/mm) were investigated. There were four blend ratios of cashmere (0, 25, 50, 75%) plus 100% cashmere. Each of the nine fibre blend combinations were replicated three times, and each was knitted into three tightness factors. The 81 fabrics were evaluated using the Wool HandleMeter, which measures seven primary handle attributes and Overall handle, and have been calibrated using a panel of experts and a wide variety of commercial fabrics. Results were analysed by ANOVA and general linear modelling. Tightness factor significantly affected all Wool HandleMeter attribute values, with the effect of tightness factor varying according to handle attribute. The Wool HandleMeter was able to detect differences between fabrics composed of superfine wool differing in fibre curvature, with lower fibre curvature wool fabrics having more preferred Overall handle and softer, looser, cooler, lighter and less dry handle attributes at some or all tightness factors compared with fabrics composed of higher fibre curvature superfine wool. Progressively blending cashmere with wool significantly improved Overall handle, increased soft and smooth handle, reduced dry, heavy and tight handle. Linear regression modelling indicated that fabric mass per unit area explained more than 50% of the variance in overall fabric handle and in combination with variations in fabric thickness and yarn elongation could explain 71% of the variance in Overall handle.

Reprint of: photostability of wool fabrics coated with pure and modified TiO2 colloids

The surface of wool fabrics was coated with TiO2 and TiO2-based nanocomposite colloids and the impact of this coating on the photostability of wool was investigated. TiO2 along with TiO2/Metal and TiO2/Metal/SiO2 sols were synthesized through a low-temperature sol-gel method and applied to fabrics. Composite colloids were synthesized through integrating the silica and three noble metals of silver (Ag), gold (Au) and platinum (Pt) into the synthesis process of sols. Four different molar ratios of Metal to TiO2 (0.01%, 0.1%, 0.5% and 1%) were used to elucidate the role of metal type and amount on the obtained features. Photostability and UV protection features of fabrics were evaluated through measuring the photo-induced chemiluminescence (PICL), photoyellowing rate and ultraviolet protection factor (UPF) of fabrics. PICL and photoyellowing tests were carried out under UVA and UVC light sources, respectively. PICL profiles demonstrated that the presence of pure and modified TiO2 nanoparticles on fabrics reduced the intensity of PICL peak indicating a lower amount of polymer free radicals in coated wool, compared to that of pristine fabric. Moreover, a higher PICL peak intensity as well as photoyellowing rate was observed on fabrics coated with modified colloids in comparison with pure TiO2. The surface morphology of fabrics was further characterized using FESEM images.

Transglutaminase mediated grafting of silk proteins onto wool fabrics leading to improved physical and mechanical properties

Transglutaminases have the ability to incorporate primary amines and to graft peptides (containing glutamine or lysine residues) into proteins. These properties enable transglutaminases to be used in the grafting of a range of compounds including peptides and/or proteins onto wool fibres, altering their functionality. In this paper we investigated the transglutaminase mediated grafting of silk proteins into wool and its effect on wool properties. A commercial hydrolysed silk preparation was compared with silk sericin. The silk sericin protein was labelled with a fluorescent probe which was used to demonstrate the efficiency of the TGase grafting of such proteins into wool fibres. The TGase mediated grafting of these proteins led to a significant effect on the properties of wool yarn and fabric, resulting in increased bursting strength, as well as reduced levels of felting shrinkage and improved fabric softness. Also observed was an accumulation of deposits on the surface of the treated wool fibres when monitored by SEM and alterations in the thermal behaviour of the modified fibres, in particular for mTGase/sericin treated fibres which, with the confocal studies, corroborate the physical changes observed on the treated wool fabric. © 2006 Elsevier Inc. All rights reserved.

Transglutaminase treatment of wool fabrics leads to resistance to detergent damage

Biological detergents are now routinely used in domestic laundry because the enzymes they contain provide the added benefit of low temperature washes with improved cleaning performance. One of the key enzymes found in these detergents are proteases, which if exposed to natural protein fibres such as wool or silk can cause irreversible damage, leading to loss of fabric strength, shape and poor colour fastness. Transglutaminases (TGases) are protein cross-linking enzymes capable of adding tensile strength to wool proteins, and as a consequence are capable of remediating the damage caused by previous chemical treatments, and more importantly, by proteases. In this paper we treated dyed wool fabric with TGase and then washed the fabric with biological and non-biological detergents to investigate whether TGases would protect wool garments from damage by the undue use of biological detergents in domestic laundry. We demonstrate using different cycles of detergent washes containing biological and non-biological detergents and different TGase treatments, that wool fabric treated previously with TGase release less dye into the washing liquor and in addition maintain fabric strength at levels greater than the washed controls. As a consequence, wool garments previously treated with TGase are likely to have increased resistance to domestic washing and thus provide increased longevity. © 2005 Elsevier B.V. All rights reserved.

A study of dimensional changes in wool fibres and fabrics

Wool fabric dimensional properties were found to be influenced by the temperature and pH of the fabric, and on the fabric tension during pressure steaming. The results show that improvements can be made to standard methods for measuring fabric dimensional properties, and to the design of commercial finishing steaming equipment.

An investigation of polypyrrole coated conductive textiles: this research aimed at clarifying some issues occurred in the research project on coloured conductive textiles

Coloured conducting textiles have shown a wide range of potential applications in heating fabrics, electromagnetic wave absorption, and wearable optoelectronic devices. This research aimed at clarifying some issues occurred in the research project on coloured conductive textiles. The investigation firstly clarified a possible chemical reaction that took place between a commercial dispersing dye (Terasil Red G) and the conducting polymer polypyrrole, through chemical separation, structural identification and spectrum characterisations. Then, a series of acidic dyes were introduced into polypyrrole matrix during the vapour coating of conducting polymer on the wool fabrics. Colour and thermal stability studies were conducted. Finally, the polypyrrole nanoparticles (particle size several~200nm) were prepared by a microemulsion polymerisation technique. An acid dye was used as the dopant to re-dope the nanoparticles. The effect of the acidic dye on the optical absorption of nanoparticles was studied. Applying the conducting nanoparticles on wool fabrics may open an alternative path to achieve the coloured conducting textiles.

Effects of variation in wool fiber curvature and yarn hairiness on sensorial assessment of knitted fabrics

Previous investigations have shown that prickle discomfort sensations of wool fabrics are primarily determined by the mean fiber diameter of the wool. It is also known that differences in wool fiber curvature (crimp) affect softness of handle of greasy wool and of wool textiles. In a replicated experiment, we investigated if wearers could detect the effect of using 17 µm superfine wool of low (74°/mm) or high (114°/mm) fiber curvature, and when the wools were blended with 17 µm cashmere (fiber curvature 49°/mm) in differing proportions, on four comfort sensations. Eight single jersey knitted fabrics were assessed under a controlled protocol using forearm sleeves made of the test fabric and a control fabric. Data (37 sensorial assessments of high curvature wool fabrics; 38 sensorial assessments of low curvature wool fabrics) were analyzed using linear mixed model analysis (restricted maximum likelihood), which included fixed effects for wool type and blend ratio and a random effect for participant. The use of a control sleeve fabric reduced variance due to participant effects by providing an anchor for each sensation over time. Wool fiber curvature affected participant assessment of breathability, comfort, feel after exercise (damp/dry) and skin feel (prickly/soft), with preferred values associated with high curvature (crimp) superfine wool. Increasing the proportion of cashmere in fabrics increased skin feel (better assessed softness). Skin feel was strongly associated with the evaluation of the fabrics by the Wool ComfortMeter and with increasing hairiness of yarns.