Spun bond polypropylene and polyester nonwoven fabrics were obtained from Mogul nonwoven industry, Turkey. The diameter of the individual polypropylene filament was approximately 0.2 microns and diameter of the individual polyester filament was 0.8 microns. The basis weights of the both nonwoven fabrics were 25 grams per square meter. The prime components of this research are polypropylene and polyester nonwoven fabrics. As polypropylene fibre has stereo-regular isotactic molecular structure, due to its high degree of crystallinity, good handling, strength and a high enough melting point for normal use, it is being used in many industrial applications, as well as in healthcare protective clothing. It has non polar and hydrophobic nature which is a good liquid repellent property. Considering its liquid barrier protection PP nonwoven is used as an outer layer in the developed surgical gown. Polyester nonwoven fabric is used as an inner layer in the developed surgical gown because of its wickability characteristics. The wickability nature of polyester nonwoven transfer the moisture from inner to outer layer through capillary action which makes the wearer comfort.
Figure 1 shows the plasma experiments conducted on the samples. Prototype downstream Atmospheric Pressure Plasma Reactor is equipped with a controlled stage and a solid state power generator. The stage was cooled using a chiller. The monomer was pumped into a lab designed heated evaporator through an equipped tube. The fluorocarbon gas used to provide hydrophobicity was C3F6. The radio frequency required to build the electromagnetic field was 600 watts. The electrode applicator height was 3 mm. The flow rate monomer was maintained as 0.6 ml/min and the exposure time was 10 seconds.
Fabric was cut into 15 cm square samples. The samples were ironed to reduce wrinkling and to give an even surface height for treatment. Samples were then mounted on the stage using double sided sticky tape. Sample surface was made as smooth as possible, and loose yarns were removed or taped down. Once stable plasma was generated, stage was turned on to move sample into the plasma field for the desired exposure time for the pre-deposition surface activation treatment. After the sample passed out of the plasma field, it passed beneath the applicator, which deposited the monomer to condense and graft activated species on the fabric surface. Monomer flow was then turned off. Stage direction was reversed, and the sample passed through the plasma field for second time to induce free radical polymerization of the monomer on the fabric surface. Fabric sample was then removed from the stage and the treatment was done on both the sides.
A schematic of the flurocarbon plasma reaction mechanism is shown in Figure 2, in which I+ refers to an ion, I* refers to a hot neutrals, the dashed lines represent energy transfer through the polymer and the curved lines represent species diffusion through the polymer. Through the deposition of a flurocarbon as an overlayer, etching of surface proceeds. CxFy radicals are the precursors to polymerize deposition followed by ion activation of surface sites. The polymer layer is formed by energetic ion sputtering and F atom etching. The polymer layer is the main inhibitor for the transport of species and delivery of activation energy to the surface. The oxygen reacts with the flurocarbon species to release etch product such as COFx. Finally by this reaction lower surface energy to the polypropylene nonwoven surface was imparted.
For the application of synthesized Titanium nano dispersion, the most widely used method of application pad-dry-cure process was used. The plasma treated polypropylene nonwoven fabric was coated with 1% nano dispersion with material to liquor ratio of 1:20 and 0.5% anionic binder. The fabric samples were immersed in the bath followed by padding through squeezed rollers at a pressure of 147 N/cm2 to remove the excess liquid. Each fabric sample was padded with the solution twice to ensure even distribution of solution. After padding, the fabric was dried naturally and then cured at 150°C for 2 min. The wet pick up was 89%. The add-on of the titanium nanoparticles was 87%. Pore size of the plasma enhanced nano finished outer nonwoven fabric was characterized using tri-nocular microscope.
The plasma enhanced fluorocarbon treated fabric samples were characterized using scanning electron microscope. Tri-laminate gown with plasma enhanced flurocarbon treated nano finished polypropylene as an outer layer, PTFE film as a middle layer and polyester nonwoven fabric as an inner layer were bonded together using a fusing machine at a temperature of 165°C with pressure of 98 N/cm2. The developed plasma treated surgical gown was tested and analyzed for the following properties such as Viral penetration analysis, antibacterial, tensile, Spray impact penetration, hydrostatic resistance and moisture vapour permeability.
Risks of healthcare workers are contamination from various blood-borne pathogens due to occupational exposure to patients’ blood and body fluids. So the antibacterial testing was performed for the developed surgical gown. Light activate antibacterial mechanism which involves interaction with and transferring energy to oxygen so as to provide a source of an active or excited oxygen species known as singlet oxygen. Singlet oxygen is an activated form of the usual triplet state molecular oxygen. Upon exposure to normal light, the dyes used in the present invention generate singlet oxygen that kills microorganisms. Bacteria require less light though they are more sensitive to the singlet oxygen generated by the light activated dye. Surgical room illumination of about 2000 foot candles is more than sufficient. Test swatches of this plasma treated nonwoven were tested for microbiological kill by inoculating the swatches.
The antimicrobial substrate so made comprises of a light activatable singlet oxygen generating substance to inhibit the growth of bacteria selected from the group consisting of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Mycobacterium bovis, methicillin resistant Staphylococcus aureus and Proteus vulgaris. The bacterial concentration was 0.5%.
Swatches with a 0.5% concentration of bacteria were exposed to light of 2000 foot candles or dark for a given period of time. After exposure for the required time, the number of live bacteria remaining on the test swatches was determined. The log of the remaining live bacteria versus the exposure time to light of 2000 foot candles and dark were determined. After a suitable incubation, bacterial colonies were counted, percent kill calculated. Recovery procedure started with transfer of samples into a sterilized capped tube containing about a dozen 3 mm glass beads and 5 ml of sterile phosphate buffered saline. After sealing the cap, the tube was shaken vigorously for one minute and then placed for 30 seconds in a low intensity ultrasonic cleaning bath. One ml of the recovery fluid was also placed directly in a 100 mm Petri plate. For one to two days the plates were incubated at 30°C., until countable. The zero time counts recovered from the swatches were compared with the inoculum count. To obtain and average log zero time reading, all of the zero time contents were combined by averaging their base 10 logarithms. Log reduction was calculated as the difference between the samples and average zero time logarithms. Percent kill was calculated as 100(1- Log10).
Viral penetration testing of surgical gown using ASTM F 1671 was carried out to investigate the antiviral property. ASTM F1671 is the test method used to measure the resistance of materials used in protective clothing for penetration by blood borne pathogens, using bacteriophage under the condition of continuous liquid contact. The test system has been designed for measuring penetration of surrogate microbe for hepatitis B virus (HBV), hepatitis C virus (HCV) and HIV. The protective clothing materials to be tested are intended to provide protection against blood, body fluids and other potentially infectious materials. The surface tension range for blood and body fluids is approximately 42 – 60 dynes/cm. In order to simulate the wetting characteristics of blood and body fluids, the surface tension of the ΦX174 bacteriophage suspension is adjusted to approximate lower end of this surface tension range (42 dynes/cm).
The ΦX174 bacteriophage was selected as the most appropriate surrogate for the blood borne pathogens mentioned because it satisfies all of these criterias. The ΦX174 bacteriophage is a non-enveloped 25 – 27 nm virus (similarly to HCV, the smallest pathogen) with an icosahedral or nearly spherical morphology and excellent environmental stability. It is non-infectious to humans, has a limit of detection which approaches a single virus particle, grows rapidly, and can be cultivated to reach high titers similar to HBV (the most concentrated pathogen mentioned). Test samples are prepared by randomly cutting the protective clothing material into approximately 75×75 mm swatches. Test samples are exposed to approximately 60 ml of the ΦX174 bacteriophage suspension. At the conclusion of the test, the observed side of the test sample is rinsed with a sterile assay medium and then analyzed for the presence of the ΦX174 bacteriophage. Surgical protective clothing ‘pass/fail’ determinations are based on detection of penetration.
