Journal of Sc ientifi c & Indust ri al Resea rch Vo l. 6 1, September 2002. pp 729-733 Comparison of Fixation Characteristics of New Acid Fixing Reactive Dyes Derived from 5, 10 -Phenophosphazine Ring with Commercial Reactive Dyes on Nylon 66 and Wool Substrates A Mamuda, K A Be ll o and M K Yakubu* Department of Textile Science and Technology, ABU Zaria, Ni ge ria Rece ived:08 October 200 1; accepted:22 May 2002 The traditi onal alk aline reactive dyes we re found un suit ab le for th e continuous dye ing of th e pol yes ter/co tt on blend s. Thi s and oth er problems l ead to th e for th e ac id fixing reac ti ve dyes. Ca lcobo nd and Procion T dyes were thus introduced . However. th ese series of dyes ha ve suffered diminishing accep tabilit y bec au se of th e ex pensi ve appli ca tion conditions. D yes derived from th e 5, I 0- phenophosphazine ring we re accidentally fo und to form covalent bo nd s with cellul ose at neutral pH ea rlier. Thi s r epo rt ex tend s appli ca tion of the se group s of dyes to wool and nylon subst rates. The effec t of pH on ex hausti on and fi xa tion was in vestigated. The kinetics of dyeing was al so studi ed and compared with so me commercial alk aline fi xing reactive dyes . The dyes have been es t:lbli shed to be ac id fixing on wool and nylon. A r eac ti on mechanism has also been proposed. Introduction Reactive dye in g systems ha ve become th e most important discovery in th e Co lourati on industry in th e las t century. Ever s in ce th ey were di scovered, diminis h- in g e ra for th e demand of other dye c la sses set in. Their maj or adva nt ages are supe ri or wet fastness properties and hi gh bri ghtne ss of colours. The ea rli er dy es produced are, however, fixed on to th e substrates by an alkaline trea tm e nt at tim es at hi gher te mp eratures. As a res ult , they form either esters or e th ers with cellulose'. Later th ese dyes were round to ha ve th e fo ll ow in g three disad- va ntages: (i) Lot of dye wastages due to hydrolysis, ( ii ) Could not be applied to cellu lose/polyester bl ends as th e di sperse dy e mean t for th e polyester compone nt was decomposed at th e te mp erature of applica ti on, and ( iii ) Du e to the hi gh alkalinity required some cou ld not be ap pli ed unt o wool and nylon s ub strates. Re searchers later introduced ano th er gro ur of reactive dyes that could fix o nt o the substrates by an ac id fixing mec ha ni sm. The first group was introduced as calcobo ncl and th e seco nd group as Procion T dyes 2 Howeve r, th ese dyes have now become obsole te. Their major di sa dv antage is th e ve ry dras ti c conditions needed to apply them. In certain cases, speciali zed equipment, i.e. baking units have to be e mpl oyed. They also ca nn ot * Au th or for co tTes Dondence be app li ed by exhaustion dyeing methods. Bello and Zhao 3 stumbled into th e 5, I 0- phenophosphazine ring dye systems which they accidentally discovered to fo rm covalent bond under neutral conditions with cellulose. Prese nt st ud y ex plores the po ss ibility of the applicabil- it y of thi s system into the area of wool and nylon sub- stt·ates. The overa ll effici ency of any reactive dyeing sys te ms depends on th e following three factor s: (i) Dif- fu sion, ( ii ) Adsorption, and ( iii ) Fixation 4 . These not only determine the fixation efficiency but also o th er important factors such as th e leve ln ess and to a certain ex te nt th e depth of penetration of th e dye. The rate at which the hydrolysed dye is washed off is also gove rn ed by the eli ffu sion rat e. For thi s reason, a very effici e nt reactive dye is one th at has just th e mini- mum amount of affinity and as a hi gh dif- fu sion coe ffi cie nt , which would increase the washoff of th e hydrolysed cly e 5 Diffusion attribute of reactive dyes is a very important proper ty and has been g iv en clu e attention by various workers 4 . Diffusion is an indirect measure of th e s ub stanti vity . i-ligh s ub stantivity me ans low diffus ion and vice ve rsa. Capponi and Senn 6 plotted relative diffusion coeffici e nt against ex haus ti on curves. The change of s ub sta nti v it y with temperature was found to be in verse to th e change of reactivity and diffusion with tempera-