Parafilm M ® Laboratory Sealing Film
Physical properties
Parafilm M ® is a semi-transparent, flexible thermoplastic,
and in its final form is a highly water proof and water resistant sheet
material. It is practically colorless, odorless, tasteless and
approximately 0.005" (e.g. 5 mils/ 127 µm) in thickness. The density
of the film is reported to be 0.992.
The unique properties of Parafilm M® make it ideal and
adaptable for many important laboratory uses and techniques. It molds and
seals itself tightly around test tubes, flasks, and various instruments and
objects with irregular surfaces. The actual composition of Parafilm M is
not actually released by the manufacturer, now ever it is described as being
a "blend of olefin-type materials". From our own experience using the
product quite extensively in our own laboratory environment, we have
generally perceived it to be close in description to that of a very low
molecular weight polyethyelene with perhaps some additional wax like
materials. That is our own interpretation of its composition and not that
of the manufacturer. In any case, the maximum use temperature seems to be
on the order of 54° C/130° F which happens to be very consistent
with the composition of the material to which is described by the
manufacturer and also our own independent perception of its composition.
We know that the film becomes soft and sticky at about 130 - 150°F (55-66°C).
In electron microscopy and histology laboratory environments, it is useful
for wrapping around, as a final kind of seal, any flask or container
containing glutaraldehyde, aqueous osmium solution, just to name a few of
its many applications in that kind of environment. Remember, for osmium
and glut, it was not meant to be the only seal, it is mean to be a
back up seal, just one more precaution to take in the event the primary
seal (e.g. the ground glass cap) should somehow become dislodged and open
up and/or fail.
It is highly insensitive to moisture vapor, moisture loss, and moisture
absorption and yet permeable to gasses sufficiently to make it ideal for
working with culture media. This property has also made it adaptable and
ideal as an "overwrap" for wet bandage and covers in the drainage cases.
The specific gravity of Parafilm M® is 0.922. There is a test done on
coal for determining its BTU value and Parafilm M® is used in the protocol
and in order to make the correct calculations, the specific gravity of the
material is needed.
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Friday July 04, 2008
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