Saran wrap

The traditional definition of a barrier polymer requited an oxygen permeabihty less than 2 nmol /(m-s-GPa) (originally, less than (1 comil)/(100 in. datm)) at room temperature. This definition was based pardy on function and partiy on conforming to the old commercial unit of permeabihty. The old commercial unit of permeabihty was created so that the oxygen permeabihty of Saran Wrap brand plastic film, a trademark of The Dow Chemical Company, would have a numerical value of 1. 

Plastic food wrap such as Saran wrap... 

Saran Wrap used in food packing is made by polymerizing a mixture in which the vinylidene chloride predominates. 

The entire trunk of the animal is covered with an impervious material (such as Saran Wrap) for a 24-h period of exposure. The Saran Wrap is secured by wrapping several long strips of athletic adhesive tape around the trunk of the animal. The impervious material aids in maintaining the position of the patches and retards evaporation of volatile test substances. 

Copolymers of vinyl chloride and vinylidene chloride are widely used (Equation 6.60). Two extremes are employed. The lesser known has a high vinyl chloride content compared with the vinylidene chloride comonomer. These copolymers are more easily dissolved and have greater flexibility. The most widely known copolymer has about 90% vinylidene chloride and 10% vinyl chloride and is known as Saran. This copolymer has low permeability to gases and vapors and is transparent. Films are sold as Saran Wrap. 

Poly(vinylidene chloride) (XLII) and its copolymers with vinyl chloride, acrylonitrile, and acrylates, usually produced by the suspension or emulsion process, are useful as oil, fat, oxygen, and moisture-resistant packaging films (Saran wrap), containers, coatings, tank liners, and monofilaments in drapery fabrics and industrial filter cloths. 

For maximum effect, cover treated area wit h Saran wrap held in place by snug-fitting shirt, mitten, or sock (never hold Saran wrap in place with tape)... 

The now-familiar plastic food wrap carton with a cutting edge was introduced in 1953 by Dow Chemical for its brand of Saran wrap. 

A large quantity of this copolymer is extruded as a thin tubing which is biaxally stretched by inflating with air at moderate temperatures before slitting. This product, called Saran Wrap, has a lensile strength of... 

Place the membrane on a glass and cover it with a layer of Saran Wrap . 

Seal the plate and wrap with Saran Wrap to avoid evaporation. 

Film Preparation. White films of polymer base and additives were prepared on sheets of Saran Wrap 49 cm in area. These films were 50 microns thickness and contained either 90-100mg of DIL or 70-80mg of DSCG. 

Acetylcholineesterase Bilayer lipid membranes were prepared by adding a solution of egg phosphatidylcholine and dipalmi-toyl phosphatidic acid dropwise into the surface of aqueous 0.1 M KC1/10 mM HEPES, near the Saran Wrap partition of a two compartment plexiglass cell. A portion of AChE solution in 10 mM Tris hydrochloride buffer solution of pH 7.4 was applied. The electrolyte level was momentarily dropped below the orifice and raised to form a membrane. The membranes were used as transducers for the reaction of AChE with ACh. An external voltage (25 mV) was applied across the membrane between two Ag/AgCl reference electrodes. Enzymatically generated hydronium ion causes transient current due to alteration of the electrostatic field by the ionization of dipalmitoyl phosphatidic acid. The response delay time was directly related to the substrate concentration where acetylcholine can be determined from 1 pM upto mM level. [113]... 

Add an equal volume of TE-buffered phenol-chloroform-isoamyl alcohol (PCI) in a 25 24 1 ratio, then cover the Corex tube with Saran wrap. Mix the solution by inverting the tubes. Be extremely careful not to spill any phenol. 

Cooling in a refrigerator freezing compartment is satisfactory. The beaker should be sealed (e.g., using Saran Wrap) to prevent escape of corrosive fumes. 

In photonic materials, the band gap is determined by geometric arrangement of a dielectric material. The underlying principle of how photonic materials work is best explained using Maxwell s equations (Joannopoulos et al., 1995). Once again, the central importance of Maxwell s equations is confronted when optical properties of materials are discussed. In photonic materials, a periodic stmcture is produced in one, two, or three dimensions. The periodic property is a dielectric constant. A trivial macroscopic onedimensional example would be a collection of individual microscope shdes separated by layers of Saran Wrap . This would produce a one-dimensional modulation in the... 

A typical roll of Saran wrap that one can readily pick up in most supermarkets (Source www.saranbrands.com). 

A graduate student in Hideki Shirakawa s laboratory at the Tokyo Institute of Technology was trying to make a polymer called polyacetylene from ordinary acetylene welding gas. The polymer, a dark powder, had first been synthesized in 1955, but no one knew much about it. Instead of a dark powder, Shirakawa s student produced a lustrous, silvery film that looked like aluminum foil but stretched like Saran wrap. Looking back over his chemical recipe, the student saw his... 

Polyvinylidene chloride is primarily extruded as a film that has low permeability to water vapor and air and is therefore used as the familiar clinging plastic food wrap, Saran Wrap. 

The reducing value is determined by adding 100 pL of the reducing carbohydrate to 100 pL of the working reagent to the wells of a 96-sample microtiter plate. The plate is covered with Saran wrap or some other method to seal the plate and prevent evaporation of the sample and reagent when the plate is heated in a water bath at 80 °C for 35 min. The plate is then cooled for 15 min and the absorbance is measured at 560 nm. Triplicate analyses are usually performed for each sample and for the maltose standards, along with a water blank [175]. 

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