2012年8月9日 星期四


Saran polyvinylidene chloride or Saran resins and films (referred to as PVDC) have been wrapping products for greater than 50 years. Saran works by polymerizing vinylide chloride with monomers which include acrylic esters and unsaturated carboxyl groups, forming extended chains of vinylide chloride. The copolymerization leads to a film with molecules bound so tightly together that quite little gasoline or water can get by means of. The result is a barrier against oxygen, moisture, chemical substances and heat-qualities made use of to safeguard food, customer and industrial merchandise. PVDC is resistant to oxygen, water, acids, bases, and solvents PVC cling film.

In 1933, Ralph Wiley, a Dow Chemical lab worker, accidentally
discovered polyvinylidene chloride or Saran. Ralph, a college student who cleaned glassware inside a Dow Chemical lab, came across a vial he couldn't scrub clean. He called the substance "eonite", immediately after an indestructible material inside the comic strip "Little Orphan Annie." Dow researchers made Ralph's "eonite" into a greasy, dark green film, which Dow known as "Saran". The military sprayed it on fighter planes to guard against salty sea spray and carmakers employed it for upholstery. Dow later got rid the of Saran's green color and unpleasant odor.
Soon after Planet War two, it was authorized for food packaging, and it was Prior Sanctioned in 1956 (Society of the Plastics Industry). PVDC is cleared for use as a food make contact with surface as a base polymer, in food package gaskets, in direct contact with dry foods, and for paperboard coating in get in touch with with fatty and aqueous foods.

Saran resins for food
contact could be extruded, coextruded or coated by a processor to meet certain packaging needs. About 85 percent of PVDC is employed as a thin layer amongst cellophane, paper and plastic packaging to improve barrier overall performance. For non-food make contact with, Saran resins may be employed for molding and melt adhesive bonding. In combination with polyolefins, polystyrene and also other polymers, Saran might be coextruded into multilayer sheets, films and tubes PVC cling film.

Saran films are
most effective identified within the type of Saran Wrap R film, the primary cling wrap created for household (1953) and commercial use (1949), introduced by the Dow Chemical Company. Saran Wrap R brand plastic film is now marketed by S. C. Johnson.

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