| Ozone（O3）washing is a water saving,environment friendly and efficient method for denim.However,after ozone washing,elastic denim often appear irreversible loss of elasticity.In this paper,the mechanism and influencing factors of elasticity loss of three kinds of elastic fibers used in denim after ozone washing were discussed.Then,the effect of ozone washing on properties of elastic denim was studied,and the best ozone washing process for elastic denim was obtained.In addition,elastic fiber of jeans and elastic denim were treated by O3/UV synergistic washing for higher treatment efficiency,and compared with the effect after traditional washing.It provides a theoretical basis for ozone washing as an efficient and water-saving washing method to extend to the whole elastic denim garment processing industry.Three kinds of denim elastic fibers,polyether spandex,polyolefin elastic fiber and polypropylene terephthalate（PTT）,were selected to study the mechanism of elasticity loss under ozone washing.The results show that the ozone mainly acts on the soft chain section（-O-CO-NH-）of spandex,which oxidizes and breaks the chain segment.Therefore it mainly leads to the elasticity loss of polyether spandex.In addition,the hydroxyl radical（·OH）is produced when the ozone is dissolved in water,which has some influence on the elasticity loss.For elastic denim fabrics containing polyether spandex,the optimal process of ozone washing was 30min of the treatment time,60%of the moisture,and 57 of the pH value.For polyolefin fibers,the fibers are oxidized and decomposed under the action of ozone,and the flexible chain breakage of macromolecules leads to the loss of elasticity of the fibers,the optimal process of ozone washing was 20min of the treatment time,80%of the moisture,and79 of the pH value.For PTT fiber,ozone destroys the ester group and flexible methylene of PTT fiber,and causes the conformation change of spring"Z"shaped macromolecule and the loss of elasticity,the optimal process of ozone washing was40min of the treatment time,60%of the moisture,and 37 of the pH value.The effects of process conditions（ozone concentration,treatment time,moisture content of fabric and pH value）on FTIR,K/S value,mechanical properties（elasticity,breaking strength,tearing strength,bursting strength and wear resistance）,air permeability and color fastness to perspiration were studied after ozone washing of elastic denim.The results show that the ozone washing technology has some influence on the mechanical properties of the elastic denim,but it has little effect on the color fastness to perspiration,which is still up to 45 grade.With the increase of ozone concentration or the prolongation of treatment time,the mechanical properties of elastic denim are decreasing,which is mainly due to the destruction and strong damage of yarn caused by ozone washing.The mechanical properties of the fabric are less damaged when the fabric is dry.However,when the moisture content of fabric increases,the mechanical properties decrease seriously.The hydroxyl radical（·OH）produced by ozone dissolved in water increases with the increase of moisture content of the fabric,which cause the oxidation damage of the fiber is more serious.In the process of ozone washing,the pH value has the greatest influence on the mechanical properties.Ozone washing in neutral environment has less loss in mechanical properties of elastic denim fabric,but under strong acid or alkali environment,the mechanical property are seriously damaged,the strength loss rate is 33%,and the wear resistance is more than half.The optimal process of elastic denim under ozone washing was 50mg/L of ozone concentration,30min of the treatment time,80%of the moisture,and 5 of the pH value.The influence of O3/UV synergistic washing on properties of three kinds of elastic fibers and elastic denim was studied,and compared with traditional washing water.The results showed that,compared with oxygen bleaching（H2O2）and chlorine bleaching（NaClO）,the mechanical properties and surface damage of three kinds of elastic fibers and elastic denim fabric were the minimum under O3/UV synergistic washing.The effect of oxygen bleaching is more serious than O3/UV.Chlorine bleaching has the most serious damage on three kinds of elastic fibers.And O3/UV synergistic washing has higher decolorization efficiency and less damage to mechanical properties of elastic denim fabrics than chlorine bleaching and oxygen bleaching. |
