| abstract |
The present invention discloses a film layer that has shrinkability when exposed to energy, such as heat. For example, a film layer is formed and stretched at a relatively low temperature in one or two directions. Specifically, the film layer is stretched near the glass transition temperature of the polymer used to form the film. It has been found that the stretchability of the film is improved by stretching the film at a relatively low temperature. In certain embodiments, the film layer comprises an unmodified polyester polymer such as polyethylene terephthalate. For example, polyethylene terephthalate can be obtained by reacting terephthalic acid with ethylene glycol or polyethylene glycol. |