Graft Copolymerization onto Wool Fibers: Graft Copolymerization of Acrylic Acid onto Wool Fibers Initiated by Quinquivalent Vanadium

Abstract

ABSTRACT:Graft copolymerization of acrylic acid onto wool fibers was carried out with quinquivalent vanadium as the initiator in an aqueous medium under nitrogen atmosphere. The percentage of grafting was influenced by reaction time, temperature, concentrations of acid, monomer, initiator and base polymer. Grafting has also been carried out in the presence of various organic solvents. It [V+ 5 ]=0.025 M, Wool =0.2 g and for a reaction time of 6 h. A suitable mechanism has been proposed for graft initiation and termination. A theoretical rate equation has been derived. The behaviour of the graft copolymers towards mineral acids and alkalis has been tested. Their tensile properties, dye-uptake ability and absorption of water and water vapour have also been examined. KEY WORDSDefatted Wool / Initiator Effect / Monomer Effect / Temperature Effect / Solvent Effect / Tensile Modulus / Dye-Uptake / Wool, a natural protein, called oc-Keratin has significant characteristics and is used for making warm garments. With a view to enhance the durability of woolen garments and to add improved properties such as better dyeability, prevention of shrinkage and pilling, improved bacterial resistance, hydroscopicity, tensile strength, thermal stability, etc. attempts have been made since 1945 to modify wool fibers chemically. This involves functionality changes via etherification, esterification, urethanation, amidation, etc. 1 -5 ; by interfacial graft condensation of polyamides, 6 -s polyurethanes,9 polyureas, polyesters, polycarbonates10 via radical grafting of vinyl monomers involving high energy radiation. Photochemical and chemical method of initiation involving metal and non-metal ion initiators" -37 and through chemical treatments.38-51 However, during recent years, * To whom all correspondence should be made. chemical methods of initiation of grafting involving metal and non-metal ion oxidisers, organic peroxides, hydroperoxides, aliphatic azo compounds like ce+4, y+s, Mn(IV), Mn(III), S 2 0~-, HS0 5 , H 2 0 2 , P 2 0~-, BPO, CHP, AIBN, etc. have attracted the attention of chemists as has been reviewed by us recently. 52 Among the chemical initiators quinquivalent V(V) has a unique identity and it is reported to oxidise a multitude of mganic substrates (alcohols, acids, aldehydes, sugars, mercaptanes) in aqueous H 2 S0 4 medium. 53 Most of such reaction proceed through a free radical path that effectively initiates vinyl polymerization. Further, quinquivalent vanadium has similar affinity towards macromolecules contammg characteristic pendant groups (-OH, -CHO, -NH 2 , -SH, --COOH, etc.) on their backbone so that the interactions ofV(V) with the groups form polymer free radicals 883

Graft polymerization onto wool fibre for improved functionality

“…This improvement in the percentage of grafting can be due to activation of the backbone of the wool where the grafting sites are generated. Higher temperature also increase the rate of monomer diffusion and mobility into the wool matrix where the grafting sites are present (Giri, Nanda et al 1989). The swellability of the fibre also increases by increasing the temperature, increase the monomer solubility, improve the rate of initiation and the propagation of the graft (Kantouch, Abdel-Fattah et al 1972).…”