• Membrane Journal
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• v.24 no.6
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• pp.438-447
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• 2014

The amorphous and porous borosilicate without any cracks was obtained under the following condition : 0.01~ 0.10 mole ratio of trimethylborate (TMB)/ tetraethylorthosilicate (TEOS) and the temperature of $700{\sim}800^{\circ}C$. According to the BET and SEM measurements, borosilicate heat-treated in between 700 and $800^{\circ}C$ showed the surface area of $251.12{\sim}355.62m^2/g$, the pore diameter of 3.5~4.9 nm, and the particle size of 30~60 nm. According to the TGA measurements, the thermal stability of poly[1-(trimethylsilyl)propyne](PTMSP) membrane was enhanced by inserting borosilicate. SEM observation showed that the size of dispersed borosilicate in the composite membrane was $1{\mu}m$. The results showed that the permeability of $H_2$ and $N_2$ increased and the selectivity of $H_2/N_2$ decreased upon the addition of borosilicate into PTMSP membranes. Addition of borosilicate may possibly increase the free volume, cavity and porosity of membranes indicating that permeation occurred by molecular sieving, surface and Knudsen diffusion rather than solution diffusion of gases.

• Membrane Journal
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• v.25 no.2
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• pp.123-131
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• 2015

The PTMSP/PDMS graft copolymer were synthesized from the PTMSP[poly(1-trimethylsilyl-1-propyne)] and the PDMS[poly(dimethylsiloxane)] and then the PTMSP/PDMS-borosilicate composite membranes were prepared by adding the porous borosilicates to the PTMSP/PDMS graft copolymer. The number-average molecular weight (${\bar{M}}_n$) and the weight-average molecular weight (${\bar{M}}_w$) of PTMSP/PDMS graft copolymer were 460,000 and 570,000 respectively, and glass transition temperature ($T_g$) of PTMSP/PDMS graft copolymer appeared at $33.53^{\circ}C$ according to DSC analysis. According to the TGA measurements, the addition of borosilicate to the PTMSP/PDMS graft copolymer leaded the decreased weight loss and the completed weight loss temperature went down. SEM observation showed that borosilicate was dispersed in the PTMSP/PDMS-borosilicate composite membranes with the size of $1{\sim}5{\mu}m$. Gas permeation experiment indicated that the addition of borosilicate to PTMSP/PDMS graft copolymer resulted in the increase in free volume, cavity and porosity resulting in the gradual shift of the mechanism of the gas permeation from solution diffusion to molecular sieving surface diffusion, and Knudsen diffusion. Consequently, the permeability of $H_2$ and $N_2$ increased and selectivity ($H_2/N_2$) decreased as the contents of borosilicate increased.