Synthesis And Adhesion Properties Of Crosslinkable Fluorinated Polyimide

Polyimide, the most promising engineering plastics in the field of aerospace and precise electronics in21th century, has limitation on its water absorbability which may lead to parts inflation and hydrolysis. As a solution, fluorinated polyimide has been paid close attention in recent years. However, the relationship between chain structure and adhesion performance is still remain further research to provide theoretical basis.This academic dissertation is focus on the fluorinated polyimide derived from monomer6FDA. In addition, terminated agent4-PEPA has been introduced into the structure to synthesize a new crosslinkable fluorinated polyimide. The fluorinated and crosslink structure has been confirmed by FTIR analysis. This fluorinated polyimide has a strong adhesion strength and weak water absorption. Moreover, with dynamic mechanical analyzer (DMA), thermogravimetric analysis (TGA), contact angle measurement (CA) and X-ray photoelectron spectroscopy (XPS), the crosslinkable fluorinated polyimide were characterized by the structure, thermodynamic properties and surface properties.The conclusions of this dissertation were drawn as follows:1. A new crosslinkable fluorinated polyimide, with high Tg (>280℃), strong adhesion strength (>21MPa) and weak water absorption rate (<1.5%), has been successfully synthesized.2. Fluorinated and crosslink structure determines the distinctive properties:CF3group with a certain value in crosslinkable fluorinated polyimide limits the movement of molecular chain, leading to strong entanglement and higher Tg. However, with the content of crosslink structure increases, Tg shows a slight decrease.3.(6FDA-ODA) structure determines the hydrophobicity of the surface of crosslinkable fluorinated polyimide. This structure shows a migration to the surface, which leads to weak adhesion strength.4. The crosslink structure of crosslinkable fluorinated polyimide forces the chain segement remain the position, which restrains the migration of (6FDA-ODA) to the surface and reduces the negative effects on adhesion strength. In addition, adhesion failure mode moves from adhesion mode to cohesion mode when crosslink happens.