Study On Antibacterial Properties Of Naturally Brown-colored Cotton Blend Products

Naturally colored cotton is one of cotton varieties with natural color,of which the products have the advantages of gentle luster,soft hand,good wearability as well as the functional characteristics,such as natural antibacterial activity,antioxidant performance,ultraviolet radiation protection properties,they are thus suitable for the development of underwear,pajamas,infant clothing,bedding and so on.It has reported that the antibacterial properties of naturally colored cotton mainly originate from the pigments in fiber.However,the structure of these pigment substances is unstable,showing the tendency of fading,discoloration and other phenomena in processing and daily use,which results in changes of antibacterial performances of naturally colored cotton products.In addition,naturally colored cotton(including brown-colored cotton)has inferior fiber quality compared with ordinary white cotton,leading to its products made up of blend fibers.Determination of the antibacterial characteristics of naturally brown-colored cotton blend products and the change rules of its antibacterial performances in processing and daily use is therefore necessary,which can provide references for the development and daily care of naturally brown-colored cotton products with antibacterial properties.In this paper,naturally brown-colored cotton and its blend products are the objects,and the antibacterial characteristics of brown cotton products and the antibacterial mechanism,as well as the effects of blending ratio,scouring,laundering and sunlight exposure on the antibacterial properties of blend samples were investigated.The main results of this study are as following:(1)Plate colony counting method and turbidimetry method were used to quantitatively test the antibacterial properties of brown cotton fibers.The results showed that brown cotton fibers have good inhibitory effects on the growth of S.aureus and E.coli,with the antimicrobial ratio of 87.9% and 79.5%,respectively,showing significant antimicrobial properties of brown cotton fibers.It is noted that the antibacterial properties of brown cotton fibers are improved to a certain extent after alkali and pectinase treatment.The antibacterial activity of brown cotton pigment was qualitatively characterized by disk diffusion method and FITC/PI dual color fluorescence method,indicating that the higher concentration pigment is at,the stronger antibacterial properties it holds.Thus,it can be concluded that brown cotton fibers' antibacterial properties derive from its pigment.And SEM images of cell surface of bacteria showed that the pigment can destroy the transport capacity of cell membrane by binding with cell membrane structure of bacteria to inhibit the normal growth and reproduction of bacteria,and eventually achieve the effect of killing the bacteria.(2)A series of brown cotton/white cotton blend products were prepared,and the relationship between blending ratio of brown cotton/white cotton and the antibacterial activities of blend products as well as the effects of alkaline scouring,pectinase scouring,home laundering and sunlight exposure on the changes of products' antibacterial properties were also studied.The results showed that with the increasing of brown cotton content,the antimicrobial properties of brown cotton blended samples were improving with the tendency of linear increase-slower increase-maintaining stability.The bacteriostatic rate of blend sample which contains around 70% of brown cotton were 91.2% and 86.1% against S.aureus and E.coli,respectively,having reached that of pure brown cotton sample,the best effect of antimicrobial activity.After scouring,the antimicrobial properties of brown cotton blend samples had improved to a certain extent,especially the lower content of brown cotton blend samples.Laundering and sunlight exposure were against the antimicrobial properties of brown cotton samples,presenting a small decline of bacteriostatic rate.The bacteriostatic rates were 68.1 % and 60.4 % against two kings of bacteria after scouring for 15 times while that were 81.5 % and 70.9 % after sunlight exposure for 15 h.In general,the brown cotton products have excellent and relatively stable antibacterial properties.(3)Brown cotton blended with different fibers(white cotton,wool,silk,viscose and polyester)was prepared according to the blending ratio of 30/70 and 70/30,and the antibacterial properties before and after laundering were investigated.Meanwhile,the variance and mean value of bacteriostatic rate of different blend samples were tested.It was found that under the same content of brown cotton fiber,the antimicrobial properties of different kinds of brown cotton blend products have little difference.There is a similar phenomenon that the bacteriostatic rate of blend samples which contains around 70% of brown cotton has reached that of pure brown cotton sample,the best effect of antimicrobial activity.Laundering has negative influence on the each brown cotton blend products.After laundering,the inhibiting effects of brown cotton/white cotton,brown cotton/wool,brown cotton/silk,brown cotton/viscose and brown cotton/polyester blend samples were gradually decreased with increasing laundering cycles.What's more,the bacteriostasis rate of blend samples is basically semblable with each other at the same laundering cycles,indicating that the antibacterial properties of blend products of brown cotton and other different fibers are only related to the content of brown cotton,and the influence of other fibers on it is negligible.