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Polyethylene. Sexv Packaging Prospect Much has been written regarding the packaging possibilities of polyethylene. Many properties recommend its use for this purpose: it is adaptable to many fabricating processes, it is flexible and at the same time has high tear resistance over a considerable temperature range, it has a low water absorption, its rate of water-vapor transmission is extremely low, and it is not considered toxic. It is relatively insoluble and quite inert chemically. T h e only common solvents which affect polyethylene (causing a slight swelling) at atmospheric temperatures are the chlorinated hydrocarbons and to a lesser extent the aromatic and aliphatic hydrocarbons. The D u Pont Co. has published a table showing the chemical resistance of polyethylene to a wide variety of materials. One of the most ingenious applications of polyethylene is the gasket designed by by Owens-Illinois and the MCA for use in polystyrene screw caps used for closures of C.5-gal. carboy bottles. This gasket must be inert to mineral acids such as sulfuric, hydrochloric, and nitric at atmospheric temperatures. Grooves are cut on the screw cap side of the gasket in a pattern similar to t he spokes of a wheel. The purpose of the grooves is to allow expansion when internal pressure reaches 10p.s.i. gage. Polyethylene liners for screw caps used as bottle closures have proved satisfactory but more expensive than other types. Recently, paper coated with polyethylene has been used for this purpose, and it is believed that it will be less expensive. Flanged bottle stoppers of polyethylene are marketed b y Kimble Glass Co. The shanks are hollow, thus providing the required flexibility. These stoppers are molded. The hole in the top is closed with a rigid disk of the same material. Seamless tubes of polyethylene of the flat and gusscted types can be extruded in a wide range of sizes. These tubes are used for fabricating bags and liners for drums and barrels as well as liners for shelf packages. The bottoms of the tubes are usually heat-sealed and the tops can be closed in a like manner after the bags are filled. These bags arc now in use for packaging some liquids and metal parts. Polyethylene coated kraft paper is used as a ply in multiwall paper shipping sacks to supply resistance to the absorption by
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the product of water vapor. It is also claimed that when this sheet is used a s the inside ply it protects the product against contamination by paper fibers. The most glamorous packaging application of polyethylene is the blow-molded bottles produced by Plax Corp. of Hartford, Conn. The bottle used by B & A division of General Chemical Co. for -18(( reagent hydrofluoric acid has had wide publicity. This container, holding a pound of hydrogen fluoride, has a cleverly designed pouring spout of polyethylene. It is a n outstanding packaging development. Hlow-molded bottles
are also used for packing shaving lotion, hair dressing, cosmetics, and talcum powder. Plax has stock molds on hand for 1-, 2-, 4-, 8-, and 16-oz. narrow mouth bottles of the Boston round type and they have 8- and 16-oz. molds in a widemouth type. These containers can be sterilized for pharmaceutical use with ultraviolet light. Blow-molded bottles are extremely flexible; thus powders and liquids can be dispensed from them by squeezing. The blow-molding process has been described in an article by James Bailey that appeared in the April 1945 Modem Plastics.
Seamless lube of
polyethylene
At present, work is under way to determine the permeability of polyethylene to various organic materials. In general, polar materials permeate very slowly but the reverse is true of the nonpolars such as carbon tetrachloride; and benzene. As the temperature increases, of course, the speed of transmission is increased. When this work has been completed, it is expected that it will be published.
mmm mm TAKES THE KINKS OUT OF WIRE CLOTH PROBLEMS Multi-Metal is your standby for wire cloth of very type and description. We make wire cloth and filter cloth—and fabricate it into units. That has been our specialty for over a quarter of a century. The unit shown here is an intake screen especially fabricated by Multi-Metal. It is coarse monel wire cloth that has been welded to a monel metal frame. Its purpose: to screen debris, keep solids out of pumps. It does the job to perfection. Write for illustrated catalog.
Wire Cloth by the Roll, Yard or Piece To the Completely Fabricated Job
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Multi-Metal WIRE O L d f H C O M P A N Y . i N e . 13S0 Garrison Ave.. New York § 9 . N. Y.
2015
