a formamide - free foam prepared by using sodium bicarbonate as a foaming agent and electron - beam irradiation for crosslinking is revealed . after copolymer and sodium bicarbonate being mixed evenly , the mixture is heated and compounded to form an intermediate . then the intermediate is pressed and injected to form a sheet . next the intermediate is irradiated by an electron - beam to form crosslinks therein . at last the intermediate is heated and foamed to get a formamide - free foam . compared with foam produced by using azodicarbonamide as the foaming agent available now , formamide - free foam not only causes no harm to human health but also gives no negative effect to the environment during recycling . thus the formamide - free foam is really environmentally friendly .