E.i. Dupont De Nemours and Company

Charles M Paulson, Jr

James R Edman

Akimitsu Tsukuda

Tsuneyoshi Miwa

Masakazu Okahashi

Mark E Faulhaber

An isotropic, biaxially stretched polyimide film prepared by casting a solution of a polyamic acid precursor in an organic solvent containing a cyclization catalyst and dehydrating agent onto the surface of a support, imidizing the polyamic acid to give a continuous self-supporting gel film containing 5-50% by weight of solids, stretching the gel film in the machine direction (MD) at a ratio of 1.1-1.9, and stretching in the transverse direction (TD) with respect to the machine direction so as to maintain a TD/MD stretch ratio of from 0.9 to 1.3.

Biaxially stretched isotropic polyimide film having specific properties

An apparatus for providing signals representative of angle of maximum absorbance .theta..sub.max, specific dichroism (.DELTA.A/A), and absorbance A of a sheet of light absorbing sheet material is disclosed.

Apparatus for measurement of specific dichroism of sheet materials

Process for preparing biaxially stretched isotropic polyimide film

A method for determining a parameter that characterizes the cross sectional shape of a running multilobal filament or yarns thereof, by light scattering analysis. The analysis is based on detecting and measuring the intensity of light scattered from the yarn in the plane of the incident beam which is oriented perpendicularly to the longitudinal axis of the yarn. By comparing the intensity of the scattered light with previously measured standard values for the particular yarn geometry being measured, using correlation techniques, the average cross sectional shape parameter can be determined.

Method for measuring shape parameters of yarn

An apparatus for measuring the degree and direction of molecular orientation in film as it advances from a stretching zone. The apparatus includes a detection circuit which receives synchronous and sinusoidal reference and analytical signals based on a beam of rotating linearly polarized light.

Growing community of inventors

Wilmington, DE, United States of America

Charles M Paulson, Jr