Novel silicone thermoplastic elastomers with tailored permeation properties

The paper deals with the synthesis and properties of thermoplastic silicone elastomers containing soft segments of dimethylsiloxane and hard urea segments. To determine structure-property relations, regarding to permeation properties, the chemical structure was varied. In this study, thermoplastic silicone elastomers, based on polydimethylsiloxane oligomers with amino groups and different diisocyanates, were synthesized. The polymers were characterized by nuclear magnetic resonance (NMR) and infrared (FTIR) spectroscopy. Thin membranes of thermoplastic silicone thermoplastic elastomers were prepared and investigated with respect to the permeation properties of organic solvents. Vials were filled with a mixture of an aromatic (toluene) and an aliphatic hydrocarbon (iso-octane) and were sealed with the polymer films. The weight loss of the vials was measured. The concentration of residual solvent mixture was detected by the relation of the peak area of the two solvents. This was investigated by the GC-MS-technique. A separation of the solvent mixture occurred. The synthesized thermoplastic silicone elastomers are highly permeable for organic solvents and have selective barrier properties. The barrier properties are influenced by chemical structure of the elastomers. Therefore, these siloxane polymers can be used as semipermeable membranes for separation of solvent mixtures i.e. in oil field applications.