Preparation method of humidity-sensitive reversible color change polyimide composite film

Abstract

The invention relates to a preparation method of humidity-sensitive reversible color change polyimide (PI) composite film. A mixed solution of polyamic acid (PAA) and color change body prepared from diamine and dianhydride, humidity reversible color change hydrated metal salt (color change body) and apolar aprotic solvent is coated on a nonporous carrier such as glass with stage heating to prepare the composite film. The preparation method is simple and easy control in preparation technology and is convenient in operation, and the PI color change film prepared by the method has good homogeneity and obvious hydroscopic color change; the color can be chosen by choosing different color change bodies, and the humidity-sensitive range is adjustable; the thermal property is stable and the dehumidification can be carried out by heating so that the color is restored for recycling and repeated use; the mechanical performance is high without cracking, and the service life is long; the chemical property is stable and non-toxic, and the color change body is not easy to loss with wide application range. The preparation method can be used for preparing packing material with moisture-absorption characteristic or preparing indication labels so as to replace the traditional humidity-sensitive color change drier and humidity indicator.

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