Posted by Diffusion-polymers.com on February 02, 2005 at 17:01:05:

In Reply to: diffusion of butane in polypropylene posted by Suneetha Burla on February 02, 2005 at 16:56:18:

Dear Suneetha Burla,

Thank you for your forum message.

Giving you one answer in a nutshell:

The diffusion coefficient of Butane in Isotactic Poly Propylene equals ~ 6E-12 m2/s at 23 degrees Celsius and 1 bar (Glass Transition Temperature is 100 degrees Celsius, i.o.w. this polymer is glassy). Mind that in case of Atactic Poly Propylene, the diffusion coefficient for Butane is significantly higher (Glass Transition Temperature of Atactic Polypropylene is -20 degrees Celsius)

While this forum is too small to deal with all your questions, please contact us via e-mail for the remainder of the answers.

Regards,

: I need some information regarding the following topics
: 1. Diffusion of liquids and gases through thermoplastic polymers. The
: temperature at which diffusion occurs would be below the polymer glasstransition temperature. In other words, the polymer is glassy. The polymer may be amorphous or semicrystalline. Candidate polymers of interest are polypropylene and polyacrylonitrile. Candidate diffusing molecules are butane gas and hexane as a liquid. Also, water and alcohol. Diffusion could be Fickian (case I) or non-Fickian (case II).

: 2. What are the most common experimental techniques used? How does one analyze the data? How does one compute solubility, diffusivity and permeability?

: 3. What theories can be used to correlate and predict diffusion through polymers? Can we do any accelerated experiments?

: 4. What happens to the polymer (i.e. what physical and chemical
: structural chages occur and why) when glassy polymers or rubber gaskets come in contact with hydrocarbon gases and liquids? What happens when they come in contact with water or alcohol containing either fragrences or insecticides?

: 5. Diffusion of a liquid through a polymer film when the liquid
: contains two dissolved solutes.