Before revision: Blowing agents (also known as 'pneumatogens') or related mechanisms to create holes in a matrix producing cellular materials, have been classified as follows: Physical blowing agents include CFCs (however, these are ozone depletants, banned by Montreal Protocol of 1987), HCFCs (replaced CFCs, but are still ozone depletants, therefore being phased out), hydrocarbons (e.g.
After revision: theBlowing agents (also known as 'pneumatogens') or related mechanisms to create holes in a matrix producing cellular materials, have been classified as follows: Physical blowing agents include CFCs (however, these are ozone depletants, banned by Montreal Protocol of 1987), HCFCs (replaced CFCs, but are still ozone depletants, therefore being phased out), hydrocarbons (e.g.