A process for the preparation of an aromatic polyimide substrate for optical displays that can be carried out during the manufacture of a display, which includes the steps of coating a solution of an aromatic tetracarboxylic acid or an aromatic tetracarboxylic acid derivative and a low molecular weight polyamic acid on a solid support and subsequent heating. The polyamic acid is prepared from non-stoichiometric amounts of 3,3,4,4-biphenyltetracarboxylic dianhydride and p-phenylenediamine.

A polyamic acid manufacturing system for manufacturing a polyamic acid is disclosed using, as raw materials, a first solution in which a polyaddition-type first polymerizable compound is dissolved and a second solution in which a polyaddition-type second polymerizable compound that reacts with the first polymerizable compound through polyaddition is dissolved. The polyamic acid manufacturing system may include: a first supply part for supplying the first solution; a second supply part for supplying the second solution; a first combining part; and a first reaction part, thereby producing a first polymerization solution in which the polyamic acid is dissolved. Further, the polyamic acid manufacturing system may include: a first supply step of supplying the first solution; a second supply step of supplying the second solution; a first combining step; and a first reaction step, thereby producing a first polymerization solution in which the polyamic acid is dissolved.

Disclosed is a method of treating a polyimide, comprising: providing a polyimide to be treated; and contacting the polyimide to be treated with a fluid to obtain a treated polyimide; wherein the polyimide comprises a first repeat unit derived from pyromellitic dianhydride (PMDA) and a second repeat unit derived from 4,4-oxodianiline (4,4-ODA); and wherein the fluid comprises a supercritical fluid, a liquid with a surface tension of 10.0 mN m1 or less under the conditions of the contacting step, or a mixture thereof. Also disclosed are polyimides obtainable by the methods of the invention, formed polyimide products comprising the polyimides of the invention, and articles comprising the formed polyimide products of the invention.

The disclosure relates to a reinforced polyamide and to a process to produce a reinforced polyamide comprising providing components being one or more polyamides, one or more dianhydrides, and one or more diamines; wherein the one or more polyamides are provided at a content of at least 60 wt. % based on the total weight of the components and wherein the one or more polyamides comprise at least one polyamide having amide groups separated by at least 10 CH.sub.2 groups; performing in situ synthesis of a polyimide by reactive extrusion of the components wherein the residence time is less than 10 minutes; and recovering a polyamide-polyimide blend being a reinforced polyamide comprising a continuous polyamide phase and a polyimide dispersed phase.