I'm not sure whether the thermal issues make this is all that implausible. PLA is commonly extruded for 3d-printing at a setting of 210-230 °C. Tin melts at 232 °C.
I've noticed that at the start of a print I detect a burning scent that quickly ends once the plastic starts streaming from the nozzle.
Wikipedia informs that above 200 °C PLA cannot be polymerized as forming lactide monomer becomes favored.
So I think that the PLA is likely not stable at the temperatures used for printing but that this doesn't cause any immediate catastrophic problems.
1 kg is much too much. This has Pyrex test tube and fume hood written all over it, although the test tubes might not be recoverable afterwards.
I wouldn't bother though.
The high viscosity of molten plastic, the large difference in density, and the mutual immiscibility of the two materials will make any kind of intimate blending of two extremely difficult even if they are sufficiently thermally compatible. You would need to design a very fancy custom built apparatus to get any kind of fine emulsification.