Flame-retarding properties of ion-exchanging groups introduced into beech sawdust

Abstract

Ion exchangers prepared from beech sawdust by introduction of weak and strong basic ion-exchanging groups were analysed with thermogravimetry, differential scanning calorimetry and limited oxygen index methods to evaluate their thermal stability and flame-retarding properties. By cross-linking with epichlorohydrin in the presence of NH 4 OH, ion exchangers in free form or in H 3 BO 3 or H 3 PO 4 form were obtained with increased thermal stability in comparison to the starting material. By cross-linking and quaternization of sawdust in one step with 1,3-bis(3-chloro-2-hydroxypropyl)imidazolium hydrogen sulfate, a material with better thermal stability and flame-retarding properties was obtained than by the previous procedure. This resulted in greater residues at higher temperatures as measured by dynamic thermogravimetry. The values of rate constants and activation energies of gasification calculated from isothermal thermogravimetric measurements decreased with improved thermal resistance similar to heat effects observed with differential scanning calorimetry. Limited oxygen index values up to 35.6% were obtained.1998 John Wiley & Sons, Ltd.