A process is disclosed for transversely stretching amorphous polyethylene terephthalate film wherein the temperature is adjusted to be substantially uniform across the web before stretching, heat is removed during stretching, and after stretching, the temperature is 1 to 15C..degree. lower and is uniform...http://www.google.com/patents/US4238443?utm_source=gb-gplus-sharePatent US4238443 - Process for transversely stretching polyethylene terephthalate film
