MTBE was purchased from Merck. The hydrophobic PEBA 2533 granulates were provided by Atochem. PEBA is the general name of a class of block copolymers in which the polyether soft segments are alternatively linked with harder polyamide segments. The physical properties of these materials can be varied in a large range by changing the nature and/or the length of the soft and hard segments. Two types of PEBA materials are manufactured by Elf-Atochem: hydrophobic PEBA materials with poly(tetramethylene) glycol soft segments and hydrophilic PEBA materials with polyethylene glycol soft segments. In this work, a hydrophobic type of PEBA 2533 was used. The number 25, 35, and 40 represents the Shore D hardness of the polymer (Sampranpiboon et al., 2000).
The PEBA polymer consists of linear chains of polyamide and polyether segment (block) in an orderly pattern. The combination of the hard polyamide segment and the soft polyether segments yields a block copolymer that exhibits a two-phase structure on a microscopic scale: a crystalline phase due to the polyamide and an amorphous phase due to the polyether. The crystalline phase allows the copolymer to behave as a thermoplastic and the amorphous phase imparts elas-tomeric characteristics (Sampranpiboon et al., 2000).
In this study PEBA 2533 was used, because it was concluded that the most suitable polymer for the separation of MTBE/water mixtures is PEBA 2533 (Durmaz Hilmioglu et al., 2005).
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