Question

why does a piece of paper wrapped around an aluminium pipe not catch fire easily?

Answer 1

As you maybe knowing that Aluminium is a good conductor of heat so when a paper is wrapped around it, the aluminium pipe absorbs the heat which results in increase in the ignition temperature of the paper so....its difficult to burn it.

Answer 2

The ignition temperature of paper is lower compared to that of aluminium. When paper is wrapped around an aluminium pipe; the ignition temperature increases. That is why paper itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not catches fire that easily.