Abstract: The invention is based on the discovery that certain chain-extending resins can be incorporated into compositions whose physical integrity is dependent upon the temperature conditions to which the compositions are exposed. The compositions do not chemically decompose upon exposure to elevated temperatures. Instead, due to the relatively low crosslink density of the compositions, when stress is applied to the compositions at elevated temperature the compositions lose physical integrity, essentially crumbling into a powdery substance. Thus, when an invention composition is used, for example, as an underfill reinforcement for a device soldered to a board, the device can be readily removed from the board at elevated temperature simply by applying stress to the underfilled assembly.