Shadi Houshyar

Preparation, characterisation, and in vitro evaluation of electrically conducting poly(ɛ-caprolactone)-based nanocomposite scaffolds using PC12 cells.

In the current study, we describe the synthesis, material characteristics, and cytocompatibility of conducting poly (ɛ-caprolactone) (PCL)-based nano-composite films. Electrically conducting carbon nano-fillers (carbon nano-fiber (CNF), nano-graphite (NG), and liquid exfoliated graphite (G)) were used to prepare porous film type scaffolds using modified solvent casting methods. The electrical conductivity of the nano-composite films was increased when carbon nano-fillers were incorporated in the PCL matrix. CNF-based nano-composite films showed the highest increase in electrical conductivity. The presence of an ionic solution significantly improved the conductivity of some of the polymers, however at least 24 h was required to absorb the simulated ion solutions. CNF-based nano-composite films were found to have good thermo-mechanical properties compared to other conducting polymer films due to better dispersion and alignment in the critical direction. Increased nano-filler content increased the crystallisation temperature. Analysis of cell viability revealed no increase in cell death on any of the polymers compared to tissue culture plastic controls, or compared to PCL polymer without nano-composites. The scaffolds showed some variation when tested for PC12 cell attachment and proliferation, however all the polymers supported PC12 attachment and differentiation in the absence of cell adhesion molecules. In general, CNF-based nano-composite films with highest electrical conductivity and moderate roughness showed highest cell attachment and proliferation. These polymers are promising candidates for use in neural applications in the area of bionics and tissue engineering due to their unique properties.

Evaluation and improvement of thermo-physiological comfort properties of firefighters’ protective clothing containing super absorbent materials

In this research, super absorbent materials were incorporated into the internal layer of the firefighters’ protective clothing with the aim of increasing absorption of sweat to improve the thermo-physiological comfort properties. The performance properties were evaluated following the standard test methods (ISO 6942:2002 and ISO 9151: 1995(E)) and the thermo-physiological comfort-related properties were evaluated by measuring the transport properties such as air permeability, water sorption and evaporation, thermal resistance and water vapour resistance of the fabric assemblies with super absorbent materials. The results indicated that it is possible to improve the comfort properties of the protective clothing by the incorporation of super absorbent materials into the internal layer. The use of super absorbent materials is likely to help in the absorption of sweat in higher amount and keeping the skin and internal microclimate dry, which in turn improves the comfort level. The performance properties of all the combinations satisfied the requirements for firefighter’s clothing as mentioned in AS/NZS 4967-2009.

The impact of super-absorbent materials on the thermo-physiological properties of textiles

The use of appropriate protective clothing systems in high-risk environments is absolutely essential. Such protective clothing may not provide the desired wearer comfort due to the complexities associated with the system. These constraints are largely due to the multiple layers involved in the protective ensemble. Firefighters’ protective clothing systems, in particular, have limited or no water vapor permeability. This prevents evaporative heat loss and leads to thermal strain and sweat accumulation. This accumulated sweat on the skin and on the internal layer close to the body causes considerable discomfort to the user due to the sensation of wetness. Extensive research has been done to improve the comfort properties of such protective clothing. This research adds yet another dimension where a new inner-layer construction has been developed with high liquid and vapor-absorption capacity that could assist in keeping the moisture and vapor away from the skin and, in addition, retain a dry microclimate close to the skin. The developed materials were tested for their biophysical properties that included tests such as thermal and water vapor resistance, air permeability and moisture management properties. Experimental results in this study indicated that super-absorbent materials, when incorporated into a woven textile material, showed enhanced wearer comfort. It was observed that these super-absorbent materials have the capability to quickly wick the moisture away from the body and, in doing so, have the tendency to keep the skin dry.

Design and evaluation of smart wearable undergarment for monitoring physiological extremes in firefighting

For workers in extreme environments, such as firefighters, thermal protective clothing is essential to protect them from exposures to high heat and life threatening risks. This study will investigate the design of a new smart protective clothing system, which incorporates sensors in the undergarment to measure physiological data, such as skin temperature, heat flux and heat rate to assess the thermal status of the worker. The aim of this paper is to outline the design of the smart wearable undergarment and the evaluation process for testing the smart undergarment in a controlled environment.

Interfacial properties of all-polypropylene composites

Abstract Preparation and characterization of novel composites, consisting of polypropylene (PP) fibres in a random poly(propylene-co-ethylene) (PPE) matrix, were investigated. These composites possess unique properties, due to chemical compatibility of the two polymers allowing creation of strong physico-chemical interactions and strong interfacial bonds. The difference between the melting temperatures of PP fibre and PPE was exploited in order to establish processing conditions for the composites. Suitable conditions were chosen so that the matrix was a liquid, to ensure good wetting and impregnation of the fibres, though the temperature must not be high enough to melt the fibres. The morphology of the composites was investigated using optical and scanning electron microscopy. Optical microscope images showed that transcrystallization of the matrix was observed on PP fibre surfaces. SEM photographs displayed a thin layer of matrix on the reinforcement, attributed to good impregnation and wetting of the fibres. Adhesion between PPE matrix and PP fibres was characterized using a microbond test inspired by a fibre pull-out technique. The results showed that adhesion was appreciably increased when PP fibres were used instead of glass fibres in the matrix. Nevertheless, thermal processing conditions of the composites caused reduction in mechanical behaviour of the reinforcement.

Effect of repeated laundering and Dry-cleaning on the thermo-physiological comfort properties of aramid fabrics

This research investigated the effect of repeated laundering and dry-cleaning on the physical and thermophysiological comfort properties such as air permeability, water vapour resistance and thermal resistance of fabrics made of meta-aramid (Nomex®) fibre. Two different types of fabric were selected for the study and subjected to repeated laundering and dry-cleaning (1, 5 and 10 cycles), which is commercially used for the care and maintenance of these fabrics. The fabric thickness, areal density, thermal resistance and water vapour resistance values increased with the number of laundering cycles, whereas the air permeability decreased due to the fabric shrinkage and swelling. On the other hand, the thickness and air permeability of the dry-cleaned fabric samples increased with the number of cycles; while the water vapour resistance and thermal resistance decreased. The scanning electron microscopy images showed the structural changes as indicated by the longitudinal fibrillation in the fabrics subjected to laundering or dry-cleaning.

Evaluation of thermal, moisture management and sensorial comfort properties of superabsorbent polyacrylate fabrics for the next-to-skin layer in firefighters’ protective clothing:

This research investigated the transport properties (such as thermal resistance, water vapor resistance and air permeability), moisture management capacity and sensorial properties of some knitted structures of superabsorbent polyacrylate in order to explore their potential as next-to-skin layers in firefighters’ protective clothing in Australia. Test results using these fabrics were compared with the currently used next-to-skin woven fabric. Three different knitted structures (i.e. jersey, rib and interlock) were selected for the study in addition to the current woven fabric in use by Australian firefighters. It was observed that the knitted fabric samples of superabsorbent polyacrylate retained higher amounts of water compared to the fabric sample currently used in the firefighters’ clothing. However, the woven fabric sample dried at a faster rate. Hence, a blended fabric of polyacrylate with the current Nomex® fabric can help in higher sweat absorption and faster drying. The thermal and water vapor resistance of jersey fabric was the lowest, which may better facilitate the transfer of metabolic heat and vapor to the environment, resulting in better thermal comfort. Furthermore, all the fabric samples showed a low coefficient of friction (∼0.2), which indicated less tactile discomfort if the fabrics are worn as the next-to-skin layer in the firefighters’ clothing. The overall moisture management properties of the fabric samples were rated as fair to good. The findings of this research suggest that the superabsorbent material has the potential to be used in place of the existing next-to-skin layer of firefighters’ protective clothing, with better sweat absorption capacity and thermal comfort.

Effect of moisture-wicking materials on the physical and thermo-physiological comfort properties of firefighters' protective clothing

In this study, a new inner-layer fabric was developed with the use of superabsorbent fibre (SAF) or Coolmax® materials for firefighters’ protective clothing. These materials have high water vapour absorption and wicking capacity to assist in better moisture management in the microclimate next to the skin, providing improved comfort to the wearer. Results obtained from the water absorption tests confirmed higher absorption. These new inner-layers were tested for thermophysiological comfort properties, such as thermal resistance, water vapour resistance and air permeability. The results indicated that it is possible to improve the comfort properties of the firefighters’ protective clothing with the incorporation of SAF or Coolmax® materials into the inner-layer. However, the mechanical properties of the fabric were significantly reduced by the incorporation of these materials into the structure. The performance of all new inner-layer combinations in regard to heat resistance satisfied the requirements for AS/NZS 4967-2009 firefighter’s protective clothing, which is essential for adequate protection.

Selective laser melted titanium alloys for hip implant applications: Surface modification with new method of polymer grafting

A significant number of hip replacements (HR) fail permanently despite the success of the medical procedure, due to wear and progressive loss of osseointegration of implants. An ideal model should consist of materials with a high resistance to wear and with good biocompatibility. This study aims to develop a new method of grafting the surface of selective laser melted (SLM) titanium alloy (Ti-6Al-4V) with poly (2-methacryloyloxyethyl phosphorylcholine) (PMPC), to improve the surface properties and biocompatibility of the implant. PMPC was grafted onto the SLM fabricated Ti-6Al-4V, applying the following three techniques; ultraviolet (UV) irradiation, thermal heating both under normal atmosphere and UV irradiation under N2 gas atmosphere. Scanning electron microscopy (SEM), 3D optical profiler, energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were used to characterise the grafted surface. Results demonstrated that a continuous PMPC layer on the Ti-6Al-4V surface was achieved using the UV irradiation under N2 gas atmosphere technique, due to the elimination of oxygen from the system. As indicated in the results, one of the advantages of this technique is the presence of phosphorylcholine, mostly on the surface, which reveals the existence of a strong chemical bond between the grafted layer (PMPC) and substrate (Ti-6Al-4V). The nano-scratch test revealed that the PMPC grafted surface improves the mechanical strength of the surface and thus, protects the underlying implant substrate from scratching under high loads.

The impact of ultraviolet light exposure on the performance of polybenzidimazole and polyaramid fabrics: Prediction of end-of-life performance

This study evaluated the deterioration in thermo-mechanical and performance properties of the polyaramid and polybenzidimazole fabric used in firefighters’ protective clothing after exposure to ultraviolet irradiation, and the effect of weathering. The performance of firefighters’ protective clothing plays an important role in protection against heat and physical threats to firefighters. However, frequent exposure to heat and ultraviolet irradiation can deteriorate performance. Test results demonstrated a 79% drop in the residual strength of polybenzidimazole/Kevlar® fabric and a 51% drop in the residual strength of polyaramid (Nomex® IIIA). The results confirmed that heat accelerates the degradation of PBI, resulting in lower performance, an important consideration for firefighters’ protective clothing. In this study, a new ‘UVPro-Tex’ sensor was developed, with the capability to record the amount of ultraviolet irradiation absorbed by the fabric. When the amount of the absorbed ultraviolet irradiation reaches a critical value, the sensor warns the wearer of the end-of-life of the garment.