Monolithic Space-Filling Porous Materials from Engineering Plastics by Thermally Induced Phase Separation

Abstract

Six different uncompounded engineering and commodity polymers were evaluated for their ability to produce space-filling monolithic entities by thermally induced phase separation (TIPS) from 22 different solvents. Attempts were first made to dissolve the polymers at elevated temperatures, selected below the boiling point of each solvent. Then the solutions of polymers that were homogeneous dissolved underwent a controlled temperature decrease to induce a phase separation as the upper critical solution temperature was passed. Twelve of the solvents gave monolithic entities by this procedure, materials that were characterized with regard to their specific surface area and pore size distribution. These measured parameters were then correlated with their macroporous morphology, assessed by scanning electron microscopy. Monolithic materials with widely different mesoporous properties were obtained with specific surface areas ranging from 169 m(2)/g to structures with essentially nonporous skeletons and distinct mesopore size distribution modes from 6 to 15 nm. The materials furthermore had a wide variation in their macroporous morphologies-among the same polymer processed in different solvents and between different polymers dissolved in the same solvent. TIPS processing therefore appears to be a viable route to prepare space-filling meso- and macroporous support materials for a wide variety of purposes in separation science and heterogeneous chemistry.

Highly Porous Polymer Structures Fabricated via Rapid Precipitation from Ternary Systems

“…The porosity of the foams as a function of their initial PLA in DCM concentration is presented in Figure . The porosity ( P ) is calculated based on the data in Table using eq . , …”

“…Here ρ and ρ o are the apparent density of the foams (Table ) and the density of nonporous PLA, respectively. , PLA density depends on crystallinity ( w c ) and is equal to w c (ρ c – ρ a ) + ρ a ; where ρ a and ρ c are the density of fully amorphous (1.248 g/cm 3 ) and fully crystalline (1.290 g/cm 3 ) PLA, respectively. Thus, ρ o in eq can be replaced by (0.042) w c + 1.248 for PLA systems.…”

“…Increasing the free energy leads to instability in the system which may be followed by phase separation. The phase inversion foaming methods induced by temperature or nonsolvent are known as thermally induced phase separation (TIPS) ,− and nonsolvent induced phase separation (NIPS), , respectively. In principal, phase separation occurs if the two-phase system has a lower free energy compared to that of the initial system. ,,, …”

Fabrication of hierarchically porous superhydrophilic polycaprolactone monolith based on nonsolvent-thermally induced phase separation

“…Phase separation is an effective method to prepare hierarchically porous materials due to the advantages of simple equipment requirement and easy operation, which can be divided by thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS). 5,[14][15][16][17][18][19] In addition, the combined nonsolvent-thermally induced phase separation (NTIPS) method are also applied to fabricate porous monolith by employing a miscible solvent mixture and by controlling the temperature. 20,21 However, the relationship of the fabrication parameters and the desired structures have not been fully elucidated.…”

Recycling of ultrahigh molecular weight polyethylene waste used for preparing high performance synthetic paper

“…Thereby, it is seldom made into membranes with routine methods such as melt stretching. Thermally induced phase separation (TIPS) is a suitable method for UHMWPE being processed into microporous membranes . Even UHMWPE has more and more widespread application, its recycle had to be further developed.…”