25 February 2021 1 1K Report

I'm a chemistry student and I'm researching the kinetic degradation of mixed plastic waste. I'm having trouble calculating the activation energy by the coats & Redfern method.

The data that I have is HDPE plastic waste from TGA heating rate 5 °C/min, 10°C/min, 20°C/min and 30°C/min with 100 ml flow rate of nitrogen. I plot the graph of ln(-ln(1-alpha)/T^2) and 1/T using linear fitting in Origin software. Alpha is (mi - mt)/(mi - mf), with mi as the initial mass, mt is the mass at time t, and mf the final mass. The slope (activation energy) will be times - R (8.314 J⋅K−1⋅mol−1) from -Ea/R = slope.

From the literature that I have read, the Ea of HDPE is around 150 - 300 kJ/mol. However, from my calculation, I got the Ea of 700 - 800 kJ/mol. There might be a miscalculation from my method. I wanted to ask,

what is the correct alpha?

Does mt mean mass at any given time?

Is linear fitting in origin software already correct?

Can I know the detailed steps to calculate activation energy from the coats & Redfern method?

It'll be such a huge help, thank you.

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