Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induce d by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The incr eased crystallinity, the width of the crystals, and the piezoelectric prope rties were the same for the first intermittent heating as for continuous he ating. Further intermittent heating for the same time duration and temperat ure had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that interm ittent heat treatment has certain critical cooling temperatures that stop t he thermal reaction and are closely related to the duration of the interval . Samples once exposed to a certain duration of heat treatment and then coo led need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.