Properties of ball milled thermally treated hemp fibers in an inert atmosphere for potential composite reinforcement

Hemp (Cannabis Sativ L.) is an important lignocellulosic raw material for the manufacture of cost-effective environmentally friendly composite materials. From an earlier experiment it was found that when hemp bast fibers were heated between 160◦C and 260◦C, there was softening of lignin leading to opening of fibers and the preliminary observations showed that heat treatment at 220◦C in an inert environment seemed to provide enough fiber without affecting the associated tissues of the fibers. However, these heat treated fibers need to be separated by mechanical action. For this experiment, hemp fibers were given heat treatment in an enclosed vessel in a nitrogen environment at 220◦C for 30 min and then they were ball milled. It was found that there was further opening of fibers upon ball milling of the heated fibers and the total number of fibers increased for the equal weight of fibers. It was not possible to find strength properties of shorter length fibers; however, the results from shorter clamping length indirectly indicated that these fibers were of higher strength. The ball milled fibers also contained copious amount of fines which must be removed before using the fibers for composite manufacturing. C 2005 Springer Science + Business Media, Inc.