Depending on its processing and thermal history , polyethylene terephthalate may exist both as an amorphous -LRB- transparent -RRB- and as a semi-crystalline material .

Depending on its processing and thermal history , it may exist both as an amorphous -LRB- transparent -RRB- and as a semi-crystalline -LRB- opaque and white -RRB- material .
