Study On Elastic Change And Dimensional Stability Of Stretch Denim In Water Washing Process

With the progress of the times,people's pursuit for clothing has not only satisfied the demand of the appearance,but also clothing comfort become the main consideration.Stretch denim garments are accepted and favorite by more and more consumers because they have high elasticity and excellent resilience,softness and comfortableness,which can reflect the physical beauty,coupled with hygroscopic and sweat releasing and does not produce static electricity.The washing processes for stretch denim are divided by for steps,desizing,enzymatic treatment,bleaching and softness.There are two problems for stretch denim washing to many washing factories,one is the loss of fabric elasticity,other is fabric shrinkage and bubbling.The objectives of this thesis are to find out the main factors affecting the elasticity of denim during whole washing process.The research work is divided into three parts.Firstly to find out a suitable one from many desizing agents by comparing their performance,then optimized the desizing conditions including the dosage of desizing agent,treatment time and temperatures.The results showed that less loss of elasticity of denim achieved by using Spandex protectant as desizing agent.Secondly,the effects of pH adjuster in enzymatic treatment,inactivation and drying methods after enzymatic treatment on elasticity change of denim were studied and found out the optimized treatment condition.The results showed that the use of amino acetic acid to adjust pH value in treatment bath,sodium carbonate to inactivate and drying at room temperature could maintain a good elastic performance of the denim.Thirdly,the effects of the bleaching processes both by potassium permanganate and sodium hypochlorite were observed.In the sodium hypochlorite bleaching system,dosage of sodium hypochlorite,treatment time and temperature were used as influencing factors in orthogonal experiment design,the optimal conditions of chlorine bleaching were obtained through the evaluation of the performance indexes after treatment.It was found that when the dosage of Spandex protector BFC was of 4g / L,dosage of sodium hypochlorite solution was of 30 g / L,the treatment carried out for 30 min at 40?,the minimum elasticity loss of the denim and better color fading obtained.In potassium permanganate bleaching system,dosages of potassium permanganate and phosphoric acid,treatment time and temperature were used as impact factors to find out their effects on elasticity change of denim,to obtain the suitable weight ratio of potassium permanganate to phosphoric acid and optimal bleaching conditions.The results showed that the minimum elasticity loss of the denim achieved bleaching carried out at 30?for 15 min with 1%(w/w)of potassium permanganate and 1%(w/w)of phosphoric acid.After the potassium permanganate bleaching,the neutralization must be carried out to clean out the manganese dioxide residues on the fabric.The stretch denim samples were treated according to the orthogonal experiment design where the dosages of sodium pyrosulfite or Manganese dust remover,treatment time and temperature acted as influencing factors.It was found that the better neutralizing performance and less elasticity loss of denim obtained when the neutralization carried out at 40? for 15 min by using 5%(w/w)of Manganese dust remover.