TIPS is the abbreviation of thermally induced phase separation, which means "thermally induced phase separation" in Chinese. Its technological process and principle are that the polymer is dissolved in a solvent with high boiling point and low volatility (also called diluent) higher than the melting point of the polymer to form a homogeneous solution.
Then cool down. During the cooling process, the system will be separated. This process is divided into two categories, one is solid-liquid phase separation (referred to as S-L phase separation) and the other is liquid-liquid phase separation (referred to as L-L phase separation).
By controlling the appropriate process conditions, the system forms a two-phase structure with polymer as continuous phase and solvent as dispersed phase. At this time, a suitable volatile reagent (extractant) is selected to extract the solvent, so as to obtain a polymer microporous membrane with a certain structure and shape.
The microporous membrane has the following advantages:
1. pore size and porosity can be controlled.
In TIPS process, the type, composition and cooling conditions of solvents are closely related to the final pore structure. The pore size and porosity can be adjusted by changing one or several conditions.
2. The structure and shape of the hole can be controlled.
The honeycomb structure, lace structure, finger holes and other structural shapes can be obtained by changing the film forming conditions of TIPS. , suitable for different purposes. The pores in the membrane can be closed, semi-closed or open, and the pore size distribution can also be very narrow.
3. The types of membrane materials are greatly increased.
TIPS can not only make microporous membrane from traditional polymer membrane materials, but also make microporous membrane from crystal cavity and a solvent-free polymer with strong hydrogen bonding at room temperature. In many TIPS studies, some semi-crystalline polyolefins can usually be successfully made into microporous membranes. Such as isotactic polypropylene (iPP), ultra-high molecular weight polyethylene (UHMW-PE) and so on.