Thermal behaviour of a series of poly[B-(methylamino)borazine] for the preparation of boron nitride fibers

The thermal behaviour of a series of poly [B-(methylamino)borazine] prepared at various temperatures ranging from 140 to 200 degrees C is studied in the present paper as potential BN fiber precursors. It was shown that the softening capability of poly [B-(methylamino)borazine] can be tailored by controlling the temperature at which polymers were prepared to achieve melt-spinning and produce high quality green fibers. Thus as-spun fibers could be next converted into boron nitride fibers using ammonia (25-1000 degrees C) and nitrogen (25-1800 degrees C) atmospheres. The quality of boron nitride fibers was shown to depend on the first part of the pyrolysis step (25 and 1000 degrees C; ammonia atmosphere) in which the great majority of the weight loss necessary for boron nitride production occurs. Ideal poly[B-(methylamino)borazine] as BN fiber precursors are those prepared between 170 and 180 degrees C. They display appropriate melt-spinnability and ceramic conversion capability. (c) 2008 Elsevier Ltd. All rights reserved.