Selectively Permeable Polymers and Gas-separation Membranes: Structure and Transport Properties

Engineering of polymers with a free volume in abrasive tool composites

“…The distribution stability at the invariable external conditions remains, but the localization of each particular EFV in a sample changes. External conditions may be consid ered as invariable both at dynamic and static loads, as the averaged frequency of vibrations of small EFVs is caused by thermal vibrations of chains segments and makes ~10 13 Hz. The vibration frequency caused, for example by the power supply in the contact zone of the tool operation is 10 3 -10 6 Hz, which is lower than the movement frequency of chains segments at least by seven orders of magnitude.…”

“…The accumulated experience indicates that there is a good reason to use the polymer characteristics related to the notion of a free volume. Contrary to the term "free volume" of inorganic glasses, which is used to denote microscale pores [11], in polymers this notion denotes the looseness of molecular packing [12], i.e., a distance between chains, which exists even at zero degrees K. This characteristic is more often used to describe diffused processes of migration of gases in polymeric gas separating membranes [13]. The free volume is related to a glass transition of polymers (temperature and time of polymeric chains relaxation) by the following equation…”

Modification of polyisoprene‐block‐poly(vinyl trimethylsilane) block copolymers via hydrosilylation and hydrogenation, and their gas transport properties

“…PVTMS has been used in industry for air separation (oxygen enrichment and nitrogen generation) with good O 2 permeability and O 2 /N 2 selectivity . Not only for air separation but also for hydrogen separation, it has been used as a high potential polymer material with high H 2 permeability and H 2 /N 2 selectivity in refineries and petrochemical industry .…”

“…PVTMS membranes have good properties for gas separation; on the other hand, they have a few deficiencies in membrane formation owing to the polymer characteristics. PVTMS is brittle, with small elongation at break ( ε = 5%) . PVTMS is also expensive and excessive consumption of the polymer occurs during integral asymmetric gas separation membrane fabrication.…”

“…PVTMS has been used in industry for air separation (oxygen enrichment and nitrogen generation) with good O 2 permeability and O 2 /N 2 selectivity. [6][7][8][9][10] Not only for air separation but also for hydrogen separation, it has been used as a high potential polymer material with high H 2 permeability and H 2 /N 2 selectivity in refineries and petrochemical industry. 11,12 PVTMS membranes have good properties for gas separation; on the other hand, they have a few deficiencies in membrane formation owing to the polymer characteristics.…”