Surface modification of coir fibers I: studies on graft copolymerization of methyl methacrylate on to chemically modified coir fibers

Abstract

Graft copolymerization of methyl methacrylate (MMA) onto chemically modified coir fiber was studied using a CuSO4–KIO4 combination as initiator in an aqueous medium in the temperature range of 50–70 °C. Concentrations or [IO4−] = 0.005 mol/l and [Cu2+] = 0.002 mol/l produce optimum grafting. The effects of time, temperature, amount of coir fiber, some inorganic salts and organic solvents on graft yield have also been investigated. On the basis of experimental findings, a reaction mechanism has been proposed. Evidence of grafting was studied from fourier transform infrared spectroscopy and scanning electron microscopy of chemically modified coir and MMA‐grafted coir. Tensile properties such as maximum stress at break, extension at break and Young's modulus of untreated, defatted, chemically treated and grafted coir fibers were evaluated and compared. Grafted coir fiber showed an increase in tensile properties such as maximum stress at break, extension at break and Young's modulus. Copyright © 1999 John Wiley & Sons, Ltd.

Surface modification of coir fibers. II. Cu(II)‐ IO initiated graft copolymerization of acrylonitrile onto chemically modified coir fibers

“…However, in our case the OH peak of the AN grafted fiber is as intense as the chemically modified fiber, which is possibly due to the large concentration of the OH group of coir fiber. A similar observation was also reported in the IR spectra of MMA grafted coir fiber 19…”

“…This may be attributed to partial dissolution of the grafted fibers with the prolonged incubation period. Similar observations were also reported while studying graft copolymerization of vinyl monomers onto pineapple leaf fiber (PALF)21 and graft copolymerization of MMA onto chemically modified coir fibers 19. Within 4 h the graft yields follow an increasing trend with the time of polymerization, and thus an optimum graft yield was obtained within 4 h of the experiment.…”

“…The cause of the decrease in the percentage of grafting in the presence of different organic solvents under the present investigations might be the decrease in the net polarity of the medium, which reduces the ease of formation of the free‐radical sites on the fiber 19. It may be reiterated here that the grafting reaction is being carried out in an aqueous medium and the addition of a small amount of another solvent in place of water reduces the net polarity of the medium for which the graft yield decreases.…”

“…As a result, IO becomes free to produce free radicals and hence induce grafting of AN onto coir. The detailed mechanism was already proposed in our previous publication 19…”

“…Thus, there are reasons for the use of this initiator system for vinyl grafting onto coir fiber. We recently reported19 grafting of methyl methacrylate (MMA) onto chemically modified fiber using CuSO 4 ‐KIO 4 as the initiating system. In the present communication we wish to report the study of CuSO 4 ‐NaIO 4 as the initiator for graft copolymerization of acrylonitrile (AN) onto chemically modified coir fiber in an aqueous medium.…”