Saran polyvinylidene chloride or
Saran resins and films (called PVDC) have been wrapping products for more
than 50 years. Saran works by polymerizing vinylide chloride with monomers
such as acrylic esters and unsaturated carboxyl groups, forming long chains
of vinylide chloride. The copolymerization results in a film with molecules
bound so tightly together that very little gas or water can get through.
The result is a barrier against oxygen, moisture, chemicals and heat-qualities
used to protect food, consumer and industrial products. PVDC is resistant
to oxygen, water, acids, bases, and solvents.
In 1933, Ralph Wiley, a Dow Chemical
lab worker, accidentally discovered polyvinylidene chloride or Saran. Ralph,
a college student who cleaned glassware in a Dow Chemical lab, came across
a vial he couldn't scrub clean. He called the substance "eonite", after
an indestructible material in the comic strip "Little Orphan Annie." Dow
researchers made Ralph's "eonite" into a greasy, dark green film, which
Dow called "Saran". The military sprayed it on fighter planes to guard
against salty sea spray and carmakers used it for upholstery. Dow later
got rid the of Saran's green color and unpleasant odor.
After World War 2, it was approved
for food packaging, and it was Prior Sanctioned in 1956 (Society of the
Plastics Industry). PVDC is cleared for use as a food contact surface as
a base polymer, in food package gaskets, in direct contact with dry foods,
and for paperboard coating in contact with fatty and aqueous foods.
Saran resins for food contact can
be extruded, coextruded or coated by a processor to meet specific packaging
needs. About 85 percent of PVDC is used as a thin layer between cellophane,
paper and plastic packaging to improve barrier performance. For non-food
contact, Saran resins can be used for molding and melt adhesive bonding.
In combination with polyolefins, polystyrene and other polymers, Saran
can be coextruded into multilayer sheets, films and tubes.
Saran films are best known in the
form of Saran Wrap ® film, the first cling wrap designed for household
(1953) and commercial use (1949), introduced by the Dow Chemical Company.
Saran Wrap ® brand plastic film is now marketed by S. C. Johnson.
The Dow Chemical Company is a global
science and technology based company that develops and manufactures a portfolio
of chemical, plastic and agricultural products and services for customers
in 168 countries around the world.
In 1897, the Dow Chemical Company
incorporates with Albert E. Convers as president.
Resins and Films
Product information: When it comes
to barrier packaging, Saran* resins and films have had the world wrapped
for more than 50 years. No other barrier system can compete with the premier
qualities of this polyvinylidene chloride (PVDC) - from Dow website.
Waldo L. Semon, invented a way to
make polyvinyl chloride (PVC) useful - History of Vinyl.
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"Method of Making Insoluble Products of Phenol and Formaldehyde"
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