Film-Forming, Peeling and Stretching of Soluble Polyimides

• Main Authors: Wang, Han-Yi, 王瀚毅
• Other Authors: Liu, Ta-Jo
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/53884869369058109459

博士 === 國立清華大學 === 化學工程學系 === 98 === The objective of this thesis is the investigation of drying, peeling and stretching of recyclable polyimide films. There are two important parts of this research; peeling of the polyimide film without defect and is how to control the coefficient of thermal expansion (CTE) by the stretching process. Understanding of formation, evaporation and drying of polyimide film is necessary before analyzing the two important issues. A dimensional drying model was developed successfully to predict the residual solvent content and drying time during solvent evaporation and drying of polyimide film. The peeling behavior of polyimide film coated on steel substrates was experimentally investigated and compared with existing models. An operating window for peeling, which is defined as a closed domain for steady and defect-free peeling, is presented in terms of peeling force vs. residual solvent content. The window is bounded by two major defects: the film becomes too brittle for peeling at high peeling force, and stick-slip striation defect appears at low peeling force. There exists a critical residual solvent content below which the adhesion between the polyimide film and the substrate is too strong, then peeling is impossible. Existing models for predicting steady peeling and the on-set of peeling defects have been modified and applied to set up the boundaries of the operating window. There also exists another operating window for drying of polyimide, and is presented in the form of drying temperature versus film thickness. The effects of uni-axial stretching on the CTE, birefringence and Young’s modulus of a recyclable polyimide film were examined. An operating window which was bounded by two temperatures and draw ratios were found first. Inside this operating window, stable and defect-free stretching was possible. CTE, birefringence and Young’s modulus of the recyclable polyimide film were measured under stretching. Values of birefringence and Young’s modulus go up as the stretching stress in the machine direction increases. On the other hand, CTE in the machine direction decreases as the stretching stress increases. A theoretical model that relates stretching conditions to birefringence and Young’s modulus was developed. CTE can also be evaluated with the Young’s modulus vs CTE data available. Theoretically evaluated physical properties are in qualitative agreement with the experimental data.