Saran (plastic)
Encyclopedia
Saran is the trade name
for a number of polymer
s made from vinylidene chloride (especially polyvinylidene chloride
or PVDC), along with other monomer
s. The main advantage of Saran film is its very low permeability
to water vapor, flavor and aroma molecules, and oxygen compared with other plastics. The barrier to oxygen prevents food spoilage, and the barrier to flavor and aroma molecules helps food retain its flavor and aroma.
Saran is best known for having been used in Saran Wrap — a thin, clingy plastic wrap
that was sold in rolls and used primarily for wrapping food. Saran Wrap is now a brand of S. C. Johnson & Son
. The Saran Wrap product is no longer composed of PVDC due to purported "environmental concerns with halogenated materials". It is now composed of polyethylene
. With this change, Saran Wrap no longer provides the excellent oxygen barrier and therefore the food spoilage prevention benefit of the original product formulation. For example, at 23°C and 95% relative humidity polyvinylidene chloride has an oxygen permeability of 0.6 cm3 μm m-2 d-1 kPa-1 while low-density polyethylene under the same conditions has an oxygen permeability of 2000 cm3 μm m-2 d-1 kPa-1.
In 1942, fused layers of original-specification Saran or PVDC were used to make ventilating insoles for boots, later adopted by the U.S. Army for use in their Jungle boot
. PVDC is also used for high-quality doll hair that is valued by collectors for its shine, softness, and its ability to retain its style and curl.
In some jurisdictions, the name Saran is a registered trademark
of the Dow Chemical Company
, while in others, it has lost trademark status and become a generic
term for these polymers. In Japan, Saran wrap is a trademark of Asahi Kasei
.
Trade name
A trade name, also known as a trading name or a business name, is the name which a business trades under for commercial purposes, although its registered, legal name, used for contracts and other formal situations, may be another....
for a number of polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s made from vinylidene chloride (especially polyvinylidene chloride
Polyvinylidene chloride
Polyvinylidene chloride is a polymer derived from vinylidene chloride.-History:Ralph Wiley, a Dow Chemical lab worker, accidentally discovered polyvinylidene chloride in 1933. While cleaning laboratory glassware, he came across a vial he could not scrub clean...
or PVDC), along with other monomer
Monomer
A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
s. The main advantage of Saran film is its very low permeability
Semipermeable membrane
A semipermeable membrane, also termed a selectively permeable membrane, a partially permeable membrane or a differentially permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion".The rate of...
to water vapor, flavor and aroma molecules, and oxygen compared with other plastics. The barrier to oxygen prevents food spoilage, and the barrier to flavor and aroma molecules helps food retain its flavor and aroma.
Saran is best known for having been used in Saran Wrap — a thin, clingy plastic wrap
Plastic wrap
Plastic wrap, cling film , cling wrap or food wrap, is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time...
that was sold in rolls and used primarily for wrapping food. Saran Wrap is now a brand of S. C. Johnson & Son
S. C. Johnson & Son
S.C. Johnson & Son, Inc. , previously known as S. C. Johnson Wax , is a privately held, global manufacturer of household cleaning supplies and other consumer chemicals based in Racine, Wisconsin. It has operations in 72 countries and its brands are sold in over 110...
. The Saran Wrap product is no longer composed of PVDC due to purported "environmental concerns with halogenated materials". It is now composed of polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
. With this change, Saran Wrap no longer provides the excellent oxygen barrier and therefore the food spoilage prevention benefit of the original product formulation. For example, at 23°C and 95% relative humidity polyvinylidene chloride has an oxygen permeability of 0.6 cm3 μm m-2 d-1 kPa-1 while low-density polyethylene under the same conditions has an oxygen permeability of 2000 cm3 μm m-2 d-1 kPa-1.
In 1942, fused layers of original-specification Saran or PVDC were used to make ventilating insoles for boots, later adopted by the U.S. Army for use in their Jungle boot
Jungle boot
Jungle boots are a type of combat boot designed for use in jungle warfare or in hot, wet and humid environments, where a standard leather combat boot would be uncomfortable or unsuitable to wear...
. PVDC is also used for high-quality doll hair that is valued by collectors for its shine, softness, and its ability to retain its style and curl.
In some jurisdictions, the name Saran is a registered trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...
of the Dow Chemical Company
Dow Chemical Company
The Dow Chemical Company is a multinational corporation headquartered in Midland, Michigan, United States. As of 2007, it is the second largest chemical manufacturer in the world by revenue and as of February 2009, the third-largest chemical company in the world by market capitalization .Dow...
, while in others, it has lost trademark status and become a generic
Genericized trademark
A genericized trademark is a trademark or brand name that has become the colloquial or generic description for, or synonymous with, a general class of product or service, rather than as an indicator of source or affiliation as intended by the trademark's holder...
term for these polymers. In Japan, Saran wrap is a trademark of Asahi Kasei
Asahi Kasei
is a Japanese company. The main products are chemicals and materials science. The company has around 25,000 employees and had consolidated sales of ¥ 1.7 trillion in 2008. It was founded in May 1931, using the paid in capital of Nobeoka Ammonia Fiber Co., Ltd, a Nobeoka, Miyazaki based producer of...
.
History
Saran was first inadvertently discovered at Dow Chemical (Michigan, USA) in 1933 when a lab worker, Ralph Wiley was having trouble washing beakers used in his process of developing a dry-cleaning product. It was initially developed into a spray that was used on US fighter planes, and later automobile upholstery to protect them from the elements. Dow Chemical later refined Saran, eliminating its green hue and ridding it of its offensive odor. In 1949, Saran Wrap was invented and quickly became a common way to store food and keep it fresh.External links
- Saran Wrap - The History of PVDC (from About.comAbout.comAbout.com is an online source for original information and advice. It is written in English, and is aimed primarily at North Americans. It is owned by The New York Times Company....
)