What happens to my nickel and polyethylene composite?

[sunchaook]

I melting mix nickel powder and polyethylene and get the composite and irradiation the material for 70Mrad (I think there will be some hydrogen generature in this process). The composite has good conductivity at room temperature. But when I put this material in a oven (150’C) for 1 hour and then cooling it it room temperature, the resistance increased by 1000times.
What happened? The nickel powder oxidated? Dose hydorgen react with nickel powder?



Aim:
The resistance will jump below 5 times after heating at 150'C for 1 hour