A kind of preparation method of moisture-sensitive reversible color polyimide composite film

Abstract

The invention relates to a preparation method of a moisture-sensitive reversible discoloration polyimide (PI) film. The mixed solution of polyamic acid (PAA) / color change prepared by diamine and dianhydride, humidity reversible discoloration hydrated metal salt (color change body), and aprotic polar solvent is dip-coated on a non-porous carrier such as glass, and gradually Composite film is obtained by heating. The preparation process of the present invention is simple and easy to control, and the operation is convenient. The PI color-changing film prepared by this method has good uniformity and remarkable discoloration after moisture absorption; different color-changing bodies can be selected, and the color can be selected, and the moisture-sensitive range can be adjusted; the thermal performance is stable, It can be heated and dehumidified to restore its color, and can be recycled and reused; it has high mechanical properties, no cracks, and a long service life; its chemical properties are stable and non-toxic, the discoloration is not easy to lose, and its application range is wide. It can be used to prepare packaging materials with hygroscopic properties or make indicator labels, replacing traditional moisture-sensitive color-changing desiccants and humidity indicators.

Description

technical field [0001] The invention relates to the preparation of a polyimide (PI) composite film, in particular to a preparation method of a moisture-sensitive reversible color polyimide (PI) composite film. Background technique [0002] Polyimide (PI) is a kind of aromatic heterocyclic polymer material containing imide groups in the main chain. It is one of the engineering plastic materials with excellent comprehensive performance, and it is easy to process and shape. Its products such as film, adhesive Compounds, coatings, laminates, etc. are widely used in high-tech fields such as aerospace, machinery, and electronics. Due to the aromatic ring in the main chain, PI film has outstanding advantages: (1) heat resistance: it can withstand extremely low temperature, such as in liquid helium at -269 ° C, it will not be brittle; high temperature resistance, the decomposition temperature is generally at About 500°C; (2) The thermal expansion coefficient of PI is 2×10 -5 ~3×10...

AI Technical Summary

Problems solved by technology

However, both dark purple thymolphthalein and dark blue bromocresol green are colorless in strong alkali, so both discoloration fails at a higher pH value; when phenolphthalein is used as an acid-base indicator, the content of phenolphthalein When the indicator is less than 0.1mmol, the indicator will be irreversibly faded when it is exposed to the air for 5-10 minutes. This is because phenolphthalein is easily oxidized in the air. When the content is too small, phenolphthalein has been oxidized before it can absorb moisture and change color; triphenylmethane There is no strong force between the acid-base indicator and the aluminosilicate, and it is unstable in aqueous solution and easy to ooze out