I am doing DTA analysis on composite of polyethylene and aluminum but I kind of didin't understand my DTA graph.
The only think I know was there is melting peak in 600~ C which is melting temperature for aluminum.
I didn't understand the S shape before 600 C
I'm using Shimadzu TA 60 for my analysis
Thanks
Most probably the peaks blow 200 oC are PE melting, those between 300 and 500 belong to PE decomposition and the highest one is Al melting. Did you make TGA as well? then you could see the weight loss as well.
The peaks are there below 200C, around 350C, around 460C and around 675C. I agree with Gyorgy. Only one more suggestion about 460C may be due to phase transformation.
The melting point of pure aluminum is 660°C, not 600. The endotherm at that temperature could be Al. I would point out, however, that Al melting will only be observed if the Al particles are fairly large. You cannot melt Al foil in air since it oxidizes to aluminum oxide before it will melt. If Al particles are very small, they will do the same thing if access to oxygen is available.
Amit Das, Gyorgy Banhegyi, and Asit Baran Samui; thank you, I think I have better insight now.
James Shelby; I do the experiment in Argon atmosphere. Yes, my aluminum content is quite big. EDS Analysis said around 40% is aluminum. But from TGA/DTA the ash is only 20%. This also confuse me.
Completely in agreement with Dr. Banhegyi, peaks below 200 °C are related with PE softening and melting (reported between 115 - 135 °C), peaks between 300 and 500 are associated with PE decomposition (see related article) and DTA signal at ~660 °C is for Al melting.
Article Kinetics of the Thermal and Thermo-Oxidative Degradation of ...
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