Material properties depend on their fabricated structure and orientation. It is thus important to develop rapid nondestructive techniques that will both allow determination of the orientation fabricated, and identify any changes that occur over time as a result of subsequent in service environmental conditions.
The present study examines the relationship between the thermal penetration time and planarity in polyimide films. Polyimides are advanced materials that have good high temperature stability, excellent dimensional stability, and excellent mechanical, electrical, and chemical resistance properties. The samples tested were specially prepared to range in orientation from three dimensionally random to highly planar. The molecular structure and orientation in the polyimide film was characterized by polarizing microscope techniques, while the thermal penetration time measurements utilized a new rapid nondestructive modified hot wire instrument.
This correlation will be the first time thermal penetration time has been measured by modified hot wire techniques and related to the internal structure of a polyimide. The work contributes to a deeper theoretical understanding of heat transfer mechanisms as they relate to orientation. Thermal penetration time evaluation could provide a new tool in the arsenal of structural characterization techniques.
This relationship between thermal penetration time and orientation is key for film manufacturers. Such a correlation has potential to speed the development cycles of new materials and assure properties during production and end-use applications.