Role of Pretreatment with Potassium Permanganate and Urea on Mechanical and Degradable Properties of Photocured Coir (Cocos nucifera) Fiber with 1,6-Hexanediol Diacrylate Mubarak A. Khan, 1 M. Masudul Hassan, 2 Rownak Taslima, 3 A. I. Mustafa 3 1 Radiation and Polymer Chemistry Laboratory, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, P.O. Box 3787, Dhaka 1000, Bangladesh 2 Department of Chemistry, MC College of National University, Sylhet 3100, Bangladesh 3 Department of Applied Chemistry and Chemical Technology, University of Dhaka, Dhaka 1000, Bangladesh Received 4 December 2002; accepted 18 November 2005 DOI 10.1002/app.23863 Published online 8 March 2006 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Coir fibers were modified with 1,6-hex- anediol diacrylate (HDDA) using ultraviolet (UV) radiation. Concentration of HDDA, soaking time, and radiation dose were optimized and found to be 30% HDDA in methanol along with photoinitiator Irgacure-500 (2%) and 120 min of soaking time registered as the better performance (polymer loading (PL) 7%, tensile strength factor, T f  1.50). Urea of different concentrations (0.5–2%) were incorporated with 30% HDDA to monitor its effect on the properties and 1% urea produced the best results (PL  25%, T f  1.82). For the improvement of the properties, the fibers were subjected to surface treatment with potassium permanganate (KMnO 4 ) of different concentrations at various treating times. En- hanced properties (PL  86%. T f  4.42) of the fibers treated with KMnO 4 (0.05%) were obtained. The KMnO 4 treated fibers were again treated with HDDA (30%) solution along with urea (1%) and found to produce the best results (PL  100%, T f  4.5). Water uptake and degradable properties of the treated and virgin fibers were obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4361– 4368, 2006 Key words: coir fiber; natural fiber; photocuring; UV radia- tion; biodegradable INTRODUCTION With the advent of synthetic fibers, the use of natural fibers like coir, jute, and sisal have been diminished to such an extent that many industries dealing with nat- ural fiber products had to be closed. But natural fibers have many advantages compared with man-made fi- bers, for example, low weight, recyclability, and bio- degradability. They are renewable raw materials and have relatively high strength and stiffness and cause no skin irritation. 1 But there are some disadvantages, such as moisture uptake, quality variations, and low thermal stability. Coir is a natural fiber, which is ob- tained from the husk of the fruit of the coconut palm. Cocos nucifera L. Cellulose is the main constituent of this fiber (43%), 2 which is a hydrophilic glucan poly- mer consisting of linear chain of 1,4- bonded anhy- droglucose unit, and also contains alcoholic hydroxyl groups. 3 These hydroxyl groups form intermolecular hydrogen bonds inside the macromolecule itself and in other cellulose macromolecules. Therefore, coir fi- ber is hydrophilic in nature and this is the most im- portant disadvantage of this fiber. Chemical modifica- tion may inactivate these groups. Previously pineap- ple leaf fiber-reinforced polyethylene composites were treated with potassium permanganate (KMnO 4 ) (as a strong oxidizing agent) and improved properties were achieved. 4 Several processes like chemical treat- ments, 5–8 photochemical treatments, 9 –14 plasma treat- ment, 15 and so forth have been developed to modify polymers and fiber surfaces To improve the physico- mechanical properties, a pretreatment of the fiber sur- face or the incorporation of surface modifier during grafting process is required. Several studies have been reported to improve physicomechanical properties of natural fibers, using different impregnating solution under gamma radiation 9,10 and UV radiation. 11–14,16 In the same way, coir fibers were also modified and enhanced properties were achieved. 17 It was previ- ously observed that both polymer loading (PL) and tensile strength of wood plastic composite were en- hanced using additives containing a carboamide group. 18 –20 Urea is very cheap and contains this group, and so it was selected as an additive. The present study deals with the modification of the me- chanical and degradable properties of coir fibers as Correspondence to: M. A. Khan (makhan@bangla.net). Journal of Applied Polymer Science, Vol. 100, 4361– 4368 (2006) © 2006 Wiley Periodicals, Inc.