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单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Mechanical Properties of Polyurethane Coated Knitted Fabrics,Introduction,Samples and working method,Results and discussion,Conclusions,1,Part1 introduction,Polyurethane-coated knitted fabrics are,of interest because they exhibit several,positive properties,and yet they are little,studied,especially those used in the,garment industry,.The advantages of,polyurethane coatings in comparison to,other polymers are greater,resistance to,abrasion and splitting,increased strength,and durability.,2,Polyurethanes are formed by the,polyaddition,reaction,of a,polyisocyanate,with a,polyalcohol(polyol),in the presence,of a,catalyst,and other,additives,.,Polyisocyanate,is a molecule with two,or more,isocyanate functional groups,R-(N=C=O)n 2 and a polyol is a molecule,with two or more,hydroxyl functional,groups,R-(OH)n 2.The reaction,product is a polymer containing the,urethane,linkage,-RNHCOOR-3.,3,There is a chance to develop coated knitted,fabrics as,protective clothing,work,clothing,sportswear,and,casual wear,more,comfortable than clothes made out,of coated woven fabric because,movements,are less restricted,if clothing is,made of,elastic knitted material.,Coated knitted fabrics are generally more,stretchable,and,elastic,than woven fabrics.,4,Part2 Samples and working method,Samples,Seven knitted fabrics,with different,structures(designations KF1-KF7)were,chosen to cover a wide interval of values,of the characteristics of elongation and,breaking forces tested(Tables 1&2).,5,They were coated under,the same conditions,on,the same coating line,with,three,different polyurethane coatings,(designated,PU1-PU3).,6,The polyurethane coatings have,nearly,equal average thicknesses and,weights,but different,mechanical properties,(Table 3).,7,As described above,the,total number,of,coated knitted fabrics was 21(7 knitted,fabrics 3 polyurethane coatings).,Working method,This time we observed mechanical,properties,before and after coating,and,formed,conclusions,on,the prediction of,their behaviour,.,The behaviour of knitted and coated,knitted fabrics in the,linear application,of force,was compared with that of the,same specimens in the case of,spherical,force application.,The samples were statistically analysed,(,descriptive statistics,hypothesis testing-t-test,regression analysis,).,8,Part3,Results and discussion,9,Elongation of coated knitted fabrics in,relation to the knitted fabric,Elongation in the wale direction,10,The knitted,fabrics elongated from 46.41%to,309.93%,which is a consequence of,their,different structures.,The coated knitted,fabrics elongated in the wale direction,from 44.41%to 382.44%.,The coated knitted fabric has a,considerably,higher average elongation,in the,wale direction in relation to the knitted,fabric-on,average about 16%,apart from,the,least stretchable knitted fabric(KF3),which was,not affected by the coating,.Namely the KF3 sample was knitted in,a power-net structure,(Table 1),where,elongation in the wale direction depends,directly on elongation properties of,the,vertically laid yarn,(and not formed into,loops).,11,T,he,t-test,shows,that there is,no statistically considerable,difference,between the mean values,of elongation of the groups of samples,tested(p=0.92),or they can be observed as the,same type of polyester coating,for,elongation in the wale direction.,12,Regression analysis,indicates the,relationship,between the elongation of the,knitted fabric and that of the polyurethane-coated knitted fabric.,cw=1.2312,kw-8.4717,The coefficient,of determination,R2=0.9915,I,t is possible to use,the regression,model,obtained for easy prediction of,the behaviour of the coated knitted fabric,and the choice of,an appropriate knitted,fabric substrate,.,13,Elongation in the course direction,The,knitted fabrics,elongated,from 34.96%to 157.93%,which is a consequence of the,different,structures of knitted fabrics and yarns,used,.The,coated knitted fabrics,elongated,in the course direction,from 96.15%,to 358.75%,.The coated knitted fabric has,a considerably,higher average elongation,in the course direction in relation to the,knitted fabric-on,average about 102%,.,14,The t-test shows that there is,no statistically,considerable difference,between the,mean values of elongation of the knitted,fabrics coated with,three different types,of PU coating(p=0.72),for the elongation,in the course direction.,Regression analysis,showed that the,relationship,between the elongation of the,knitted fabric and the coated knitted fabric,in the course direction have only a,medium,correlation,(r=0.79).The relationship between variables is,not linear,.,Exponential regression model,cc=103.53,e,0.,0064,kc,with a,coefficient,of determination R2=0.6262,is the,best explanation of,elongation variance,in the course direction of the samples of,coated knitted fabrics(ecc)studied with,regard to the elongation of the samples of,the same knitted fabrics(ekc)examined.,15,It is interesting to investigate,which e
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