Study Effect Coronadischarge on Morphology , Wettability and Antibacterial of Leather

Corona discharge has been used widely to modify polymer and textile materials because it can be operated at an atmospheric pressure in air.This method has been confirmed to be simpler and more practical than any other chemical and physical methods because the samples can be quickly treated under atmosphere pressure and it is environmentally friendly too. In this study, we have studied wettability and antibacterial modify surface leather treatment by corona discharged. An element analysis was done to elucidate the change of chemical composition on the leather surface. The morphology of the modified surfaces also were investigated using scanning electron microscopy (SEM) .The results showed a significant increase in the wettability and antibacterial after treatment leather surface with corona discharge. Micrographs of SEM showed that, with an increase in power and a greater number of passages in the corona treatment, were increased cracks and hoes on the surface samples treated with corona.


INTRODUCTION
Corona discharge has been proved to be a useful method for improving the polymer surface hydrophilic property, especially in the composite material strength improvement (Weilinet al.,2202;  Strobelet al., 1999; Leeet al., 1992; Lanauzeet al.,  1990; Ogawaet al., 2201)the treatment can improve the surface affinity and the sticking strength with researchers have introduced the corona discharge treatment into the textile surface treatment to improving the wool fabric printability (Ryuet al., 1991) or the wool fabrics shrink resistance properties (Bateupet al., 1981;Belinet al., 1983).Corona discharge technology is also increase wetability and soil repellency reduce the tendency to generate a static charge, increase fabric abrasion resistance and improvecarding spinability and cotton properties after mercerization and cause the depolarization of denim (Wakidaet al., 1993;  Carneiroet al., 2000).The treatment has been confirmed to be simpler and more practical than any other chemical and physical methods because the samples can be quickly treated under atmosphere pressure.(Ogawaet al., 2001) The purposes of this research are firstly to investigatethe surface chemical composition of the untreated and corona treated leathers, secondly to study the influence of corona treatment on the antibacterial properties, thirdly to investigate wetability the treated and untreated corona leather.

MATERIALS AND METHODS
Leather was provided by Charm SaziMojtahedi .Co (Tabriz Iran).The samples for further treatment were prepared in the size of 15.0cm*15.0cm.The samples were treated by corona discharge at two levels of power (500 and 1000w) for a number of passages each of 5 and 10 by corona dischargegenerator which was designed and constructed by Ghaemshahr Azad University (Iran).The equipment utilized had the following specification: velocity 2 m/min, distance between electrodes 3mm. the instrument consists of two electrodes: a metal electrode roll with silicon coating and an aluminum electrode parallel with it.The velocity of the roll was changeable and for this study was set at 2m/min.The antibacterial properties of samples leather were measured by ATCC-100 test method (antibacterial activity assessment of textile materials).The samples were placed on a germcontaining agar plate and were inoculated with gram positive staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 8099).Specimens corresponding to untreated controls of the some material were placed in intimate contact with the nutrient agar, which previously had been streaked with inoculums of the test bacterium.After incubation for 24h, we evaluated the antibacterial properties of both the untreated and the treated leathers.
Percent reduction of bacteria (%) = A: the number of bacteria on the untreated leather B: the number of bacteria on the treated leather after 24h.
The morphologies of the samples were observed with scanning electron microscope (SEM) and elemental analysis was conducted with EDAX spectra.The samples were coated with gold beforeSEM testing.The wettability measurements for all samples (treated and untreated leather) by using a micrometer pipette, while the first: liquid drops were dispersed on each leather samples, then we calculated the time adsorption of liquid drop with samples.

SEM Observation
Corona treatment influences the morphologies and Structures of leather greatly.The morphologic changes of leather after corona treatment can be seen clearly from SEM images.Fig1.Shows the morphology of original and corona treatment leathers.
It is obvious that, with an increase in power and a greater number of passages in the corona treatment, were increased cracks and hoes on the surface samples treated with corona.This is attributed to the etching effect caused by the bombardment of the air plasma species on the leather samples surface.

The microstructure characterization
The characteristic peaks for different  It is important to note Ag, Fe and Zn appeared on the samples treated surface.Therefore it can be suggested that the antibacterial properties of samples treated with corona be related to appear this ion metal.

Antibacterial property
Table I shows the antibacterial effect of corona treatment on leather samples.It can be seen that the antibacterial efficiency against E.coli and s. aureus was higher than 68% for samples treated with corona .

Effect on wettability
The effect of corona treatment on wettability of leather samples was shown in Fig. 3.The results indicate the corona treatment improved the hydrophilicity of leather and with increase of treated voltage; high energy leads to an obvious increase in wetting properties.It was mainly ascribed to the breakage of macromolecule bond resulting from the bombardment of high-energy particle.
These results could be related to the free polar component of the leather surface while these free radicals contacted with air and more hydrophilic constituents such as carboxyl groups formed in the leather surface, which increased the wetting properties of leather.

CONCLUSION
The leather surfaces can be modified to be more hydrophilic by corona discharge.Good hydrophilic property was observed around 1000w when the leather surface was treated at 10 passages by corona discharge.The leather surface treated with corona can be used as antibacterial treatment.The antibacterial efficiency against Saureus and E-coli was higher than 70% for samples treated with corona.A rougher surface fabric is a good padding cloth and a rougher fabric surface is important in the conventional aqueous textile finishing and dying processing because of the higher rate ofliquid uptake.