the invention provides a polymer adapted for use in melt processes , the polymer having a thermally reversible bond which is adapted to evanesce at an elevated temperature and revert to a thermally reversible bond upon cooling to ambient temperature so that the polymer is adapted , upon being heated to the elevated temperature , to dissociate into melt processable polymeric fragments and , upon being cooled to ambient temperature , to re - associate . the thermally reversible bond is a bond that is capable of evanescing at a temperature which is lower than the degradation temperature of the polymer fragments . the thermally reversible bond may be , for example , a thermally reversible aromatic urethane bond .