| 摘要 |
A process is provided for making a distinction between solid, porous materials, e.g. thermoplastics, having surfaces which are either untreated or treated to render them measurably impermeable to volatiles. The surfaces are first exposed to a high concentration of a volatile fluid which is removed after a fixed time period. The surfaces are then exposed to an environment, e.g. a vacuum, to cause the volatile fluid to back-diffuse and the fluid that back-diffuses is measured. The rate at which the fluid back-diffuses from the untreated surface is considerably greater than that of the treated surface.
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