“…Poly(ethylene terephthalate) (PET) is one of the most important engineering plastics, which has been widely used as a raw material in the manufacture of fibers, packaging, optical devices, and appliances due to its excellent film‐forming property, weather resistance, and transparency (amorphous PET) 1 . The processing of PET involved many physical transformation, such as glass transition, 2,3 crystallization, 4–6 recrystallization, 7,8 double melting 9 and so on. These physical transformation will have effects on the dimensional stability (bending, creeping, softening and so on) and mechanical properties on the resultant PET products.…”