| 摘要 |
Heat-shrinkable films and heat-shrinkable tubing of linear polymeric esters that shrink at least 21/2 times as much along one of the longitudinal and transverse axes of the films and tubing as they do along the other. The films and tubing shrink between 2 and 20 percent in the direction of least shrinkage and at least 20 percent in the direction of most shrinkage. A film of the invention is prepared by stretching it in a first direction at a temperature that is above the second order transition temperature for the polymer of the film, then thermally conditioning the film while it is in the stretched condition by heating it for several seconds at a temperature that is at least 5 DEG C. above the first temperature, and then stretching the film in a second direction perpendicular to the first direction at a temperature at least 5 DEG C. above the first temperature.
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