Parafilm
Parafilm is a stretchable, whitish translucent sealing film made of - about 50:50 - paraffin wax and polyolefin ( polyethylene ), manufactured by Pechiney Plastic Packaging (formerly: American National Can Company ). In the chemistry laboratory, it is used to close various vessels (including those with irregular edges, pouring spouts) in order to largely avoid spilling, contamination and evaporation. In biological laboratories, Parafilm, or its competitor Nescofilm, is used to seal Petri dishes. This procedure is mostly used in cell and tissue culture and prevents the explants and the medium from drying out and contamination by bacteria or fungi.
properties
It is one of the simplest and most common tools in everyday laboratory work and has been on the market since around 1980 in roll form with release paper. The elasticity allows the use of similar commercially available cling film for the kitchen. The advantages of Parafilm are:
- thicker (0.127 mm) and significantly more elastic (up to + 200%). Elongation at break: 300%
- resistant to a wide variety of chemicals
- not resistant to benzene , chloroform , diethyl ether , carbon tetrachloride , toluene
- low gas and water vapor permeability
- only sticks to itself if it has already been stretched
- not poisonous
Application areas and conditions
Parafilm can be used from −45 to +50 ° C, is resistant to acids, alkalis, and some alcohols, and can be stored for three years. However, it leaves small traces on the vessel, melts at 60 ° C ( flash point 301 ° C) and is dissolved by volatile, non-polar organic solvents such as petrol or ether or may even be lifted off under their vapor pressure.
By gently heating the overlapping edges and applying finger pressure, they can be fused together. With a little practice, vessels can be sealed airtight and liquid-tight.
Compared to the watch glass , Parafilm is advantageously light, space-saving and unbreakable. There are also lightweight, break-proof watch "glasses" made of PTFE plastic , which can withstand higher temperatures. Cheaper aluminum foil is also used for sealing and insulating, but it is attacked by acids and alkalis, does not adhere, does not seal, but reflects light and heat radiation.
Due to its hydrophobic character, Parafilm is an ideal temporary storage for individual drops of watery liquid.
The film is used by model makers to mask models while painting. This is done by stretching narrow strips of the material and then letting them rest for about a minute before attaching them. Likewise, an epoxy bond can be brought into shape by coating and the film can be peeled off again after hardening with practically no residue.
Brand name
Parafilm is a brand name of the Bemis Company , USA.
Individual evidence
- ↑ Product description on the Bemis website accessed on March 2, 2016.