A foam question for the experts here.

Back after the Columbia accident, there was talk here in the group that the
early foam used on the ET was better than the type of foam used on the
Columbia ET and thereafter, because the new foam formula these days is worse
because its manufacture had to be made with more environmentally friendly
chemicals. ie. they aren't allowed to make a strong foam because of the
chemicals and new environmental laws.

Is this true or myth?