| abstract |
The present invention teaches an oriented film and method for making the same. It has been found that an olefinic film, e.g. polyethylene, can be made with highly oriented crystalline phase unit cells. The film of the present invention has crystalline phase unit cells with an a-axis highly oriented in the machine direction and consequently, the improved physical properties. Specifically, the film has a good cutterbar tear, a high degree of puncture resistance and limited tear propagation in the transverse direction. The film is made by controlling the heat transfer of a chill roll to the olefinic extrudate. Heat transfer is accomplished by pinning the olefinic film with an air knife as it is extruded on the chill roll. The pin is controlled by adjusting the temperature of the chill roll and the focus velocity of th air knife. |