[Jinan]

Dear All,

I am synthesizing a mixed matrix PVA-mordenite membrane for direct methanol fuel cell. I did the same procedure several times. The last two times, I faced a problem when casting the membrane using the film applicator device. The membrane did not come out flat. There was big holes formed. Firstly, these holes was spread homogeneously but after seconds some holes stretched and others disappear. Have any one faced such a problem before? I am attaching photos for the membranes with holes.


I synthesized the membrane using the same procedure before and I didn't face any problem like this. I didn't change any parameter in my experiments. I can't understand why this happened the last two times?!

Note: The procedure that I am using is as follow :

Membrane synthesis began by stirring 1 g of mordenite in 5 ml water for 18-20 hours until a homogeneous, white, milky-looking suspension containing no visible solid particles is obtained.

Then, 1.5 PVA was mixed with 30 ml of water for 1 hours at approximately 100°C (using a boiling water bath with the flask containing the polymer solution in the middle).

Meanwhile, the zeolite suspension was mixed using a Branson 2510 ultrasonic bath. In order to prevent the formation of high-temperature spots, once every five minutes stirring was carried out, for five minutes. This cycle was continued for an hour; therefore the total time of ultrasonic stirring would correspond to 30 minutes, with another 30 minutes of regular stirring in between.

After all the polymer and zeolite were separately dissolved, two solutions were mixed and then stirred together for approximately 4 hours at a temperature of 60°C.

At this point, the membrane solution was ready to cast using film applicator device

Best Regards

[Enthalpy]

Hi Jinan,

This suggests me a change in the wetability of the surface by the liquid. If you believe the liquid hasn't changed, you might experiment varied ways to clean and degrease the solid.