E.i. Dupont De Nemours and Company

William D Garlington

Isadore Swerlick

Stanley B Levy

Film of a wholly aromatic polyamide, at least 85% of the repeating units of which are meta-phenylene isophthalamide units, which is undrawn and noncrystalline and which has improved impact strength. Such film is made by heat-treating film of the polyamide which is undrawn and noncrystalline at 400.degree. to 300.degree. C. for from 2 seconds to 2 minutes while maintaining the film at constant length and width permitting it to shrink by at most 20% in each of the length and width.

Casting films of polymers of meta-phenylene isophthalamide

Film of a wholly aromatic polyamide, at least 85% of the repeating units of which are meta-phenylene isophthalamide units, which is undrawn and noncrystalline and which has improved impact strength. Such film is made by heat-treating film of the polyamide which is undrawn and noncrystalline at 400.degree. to 300.degree. C. for from 2 seconds to 2 minutes while maintaining the film at constant length and width or while permitting it to shrink by at most 20% in each of the length and width.

Film of aromatic polyamide and process therefor

An apparatus for stretching polymeric film is disclosed wherein a heating unit is located slightly above and between the parallel tracks of a tenter frame and wherein the heating unit includes an air duct with an air entrance opening and a series of apertures directed between the tenter frame tracks wherein the air duct is separated, by internal intermediate walls, into adjacent isolated zones extending parallel with the tracks of the tenter frame and wherein each isolated zone includes a heater. Air introduced into the duct is conducted through the zones where it is heated and directed through the apertures onto a web of polymeric film moving in the tenter frame prior to stretching.

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Wilmington, DE, United States of America

William D Garlington