| PDMS is a kind of pervaporation membrane material with excellent comprehensive properties.It was used to separate ethanol from ethanol solution.It will significantlly improve the permeability and mechanical properties when modified nanosilica was added to the PDMS precursor.At present,few kinds of silane coupling agents were chosen at home and abroad.However,it didn't have any papers reporting what the effect of silane coupling agent with different structure on performance of modified SiO2/PDMS membranes.In this dissertation,five polydimethylsiloxane?PDMS?precursors with number-average molecular weight of 26.6 K,35.5 K,50.2 K,71.7 K and 110.4 K were used as membrane materials.Hexane was used as solvent.Tetraethyl orthosilicate?TEOS?was used as crosslinker and dibutyltin dilaurate?DBTOL?was used as catalyst to prepare pure PDMS network at room temperature.PET non-woven was used as support layer to prepare PET/PDMS composite membrane.Effects of the PDMS precursor molecular weight and feed concentration on the pervaporation performances of the PET/PDMS and the pure PDMS membranes were investigated by separating ethanol from aqueous solution.In another part,the effect of four coupling agents with different non-hydronlytic groups on performance of modified SiO2/PDMS membranes was researched,when PDMS precursor with 35.5 K molecular weight was as the membrane material and the content of nanosilica was 5 wt%.The four silane coupling agents were 3-aminopropyl triethoxysilane?APTES?,ethyltriethoxysilane?ETES?,octyl triethoxysilane?OTES?and phenyl triethoxysilane?PTES?.The influence of the silane coupling agent types,their content and the feed concentration on the separation property of the SiO2/PDMS composite membranes was also researched.The results showed that the separation performance of the PET/PDMS composite membranes was better than the pure PDMS membranes.With the increase of the PDMS precursor molecular weight,the flux decreased and the separation factor firstly increased and then decreased.It had a maximum separation factor when the molecular weight was 35.5 K.The separation factor of the PET/PDMS membrane was 8.43 and 6.58 for the pure PDMS membrane.When the feed concentration increased,both of the flux and the separation factor increased.The separation factor of the composite membrane was larger than the pure membrane.The tensile modulus of the SiO2/PDMS composite membranes was firstly increased and then decreased when the APTES,PTES and OTES were added.The tensile modulus increased with the raising of the ETES content.When the length of the non-hydrolytic groups increased,the flux and separation factor of the SiO2/PDMS composite membranes decreased accordingly.It was found that the SiO2/PDMS composite membrane modified by ETES obtained a better pervaporation performance when compared with others.When the ETES added,the flux of SiO2/PDMS composite membrane was firstly increased and then decreased.The pure water flux was about 60-70 g/m2·h and ethanol flux was about 730-800 g/m2·h.For 7.3 wt% ethanol solution,the flux was 330-380 g/m2·h.The separation factor increased firstly and then decreased in 7.3 wt% ethanol solution.It had a maximum separation factor when the ETES content was 4.07×10-3 mol/g and the separation factor was 16.26.21 kinds of organic solvent were used for the measurement of the Hansen solubility parameters of the PDMS precursor.The relationship between five key parameters??D,?P,?H,?t and Ra?and the swelling degree in four liquids was investigated.It was found that the measured polar solubility parameter ?P of the hydroxyl-terminated PDMS precursor was 0.12 MPa0.5.A perfect linear relationship existed between log?Q?and ?P.It indicated that the polar interaction was the primary effect for deciding the swelling degree of PDMS network in water/ethanol system. |
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