Graft copolymerization of methylmethacrylate onto caesarweed fibers by the potassium permanganate–toluene redox system

Abstract

SYNOPSISPreliminary investigations have been conducted on the graft copolymerization of methylmethacrylate onto Caesarweed fiber, initiated by potassium permanganate and the toluene redox system. The percentage graft yield increased with permanganate up to 132% in the concentration range, 1.0 X lo-* to 5.0 X lo-' M at 4OoC. The effects of varying concentrations of toluene, acids, and monomer on graft yield were also investigated. Graft yield increased initially and then decreased on varying the concentrations of toluene from 2 X lo-' to 20 X lo-* M. The graft yield increased with temperature between 20 and 5OOC.At 60°C, the graft yield decreased considerably by up to 60% of the value at 50°C. The calculated activation energies for the overall reaction, and for the initiation process, are 9.15 and 9.30 Kcal mol-' , respectively. 0 1993 John Wiley & Sons, Inc. I NTRO DUCT10 NGrafting of synthetic polymers onto cellulosic and protein fibers has received considerable attention because, in some cases, grafting yields copolymers with improved physicochemical properties with industrial and commercial value. Specifically, grafting of acrylonitrile onto jute fibers13 resulted in the fibers' improved extensibility and light fastness. Similarly, grafting of methylmethacrylate onto jute fibers l4 yielded a copolymer with an enhanced thermal property. However, for cellulosic fibers, different morphological features of the polymer matrices are known to account for varying grafting characterist i c~. '~,~~ Caesarweed, Urenu lobatu I, is of the mallow family, Malvacea, which is one of the most important of all fiber plant families. The plant is cultivated in warm regions of several countries, including West Africa, and it often grows wild in abundance. The bast fibers are cellulosic materials, closely resembling jute, but somewhat shorter and coarser. The * To whom correspondence should be addressed. fibers are used as substitutes for jute and find local application in the production of twines and sacks. Information about the chemical composition and morphological properties of the fibers is sparse; neither is there any report on the grafting of synthetic polymer onto the fibers. This article presents the results of a preliminary study of the graft copolymerization of methylmethacrylate ( MMA) onto Caesarweed fibers, initiated by acidified potassium permanganate and the toluene redox system. EXPERIMENTALToluene (BDH) was treated with sulfuric acid and was washed copiously with distilled water to neutral pH. It was dried over anhydrous calcium chloride and was fractionally distilled before use.Methylmethacrylate ( Aldrich Corp.) was washed with 5% aqueous sodium hydroxide and sodium chloride solutions, was dried over anhydrous calcium chloride, and was then fractionally distilled. The middle fraction of the monomer was collected and was stored under refrigerated conditions. All other reagents, that is, potassium permanganate, glacial acetic acid, and sulfuric acid (-18 645

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