assuming all the solvent has been evaporated, dmt freebase could safely be stored in a plastic container without damaging said container.
however...over time (stored at RT), dmt may stick to the plastic, and you'd need to use a solvent to dissolve it, or convert it to a salt and evaporate the water.
dry the solvent containing the dmt over MgSO4, evap the solvent completely, and store in an HDPE container in the freezer.
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