If TGA of polyimides is carried out in air the mass obtained at the end is char yield or residual mass only. How we find the char yield from TGA data
To determine char yield of your polymer, heat it in an ineert gas (nitrogen) up to 700 or 800 C and monitor weight loss. Change the gas to air and continue temperature ramp to 1000C. The difference in mass between the sample heated in the inert gas and air divided by the original sample weight is the char yield of the polymer. The residual mass is the weight left after the char has been burned off (oxidized).
Char yield is usually defined as the % of solid amount you obtain at end of pyrolysis.
Residual mass is broader and usually employed for % solid after heating in oxidizing environment at high temperatures (metallic impurities, ashes, etc...).
Char yield means the remaining mass after completely degrading the substance including residual carbon. Residual mass signifies the mass remaining at particular temperature during heating.
To determine char yield of your polymer, heat it in an ineert gas (nitrogen) up to 700 or 800 C and monitor weight loss. Change the gas to air and continue temperature ramp to 1000C. The difference in mass between the sample heated in the inert gas and air divided by the original sample weight is the char yield of the polymer. The residual mass is the weight left after the char has been burned off (oxidized).
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