Polyethylene properties and uses pdf

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polyethylene properties and uses pdf

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Polyethylene PE , light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins. It is the most widely used plastic in the world, being made into products ranging from clear food wrap and shopping bags to detergent bottles and automobile fuel tanks. It can also be slit or spun into synthetic fibres or modified to take on the elastic properties of a rubber. Ethylene C 2 H 4 is a gaseous hydrocarbon commonly produced by the cracking of ethane , which in turn is a major constituent of natural gas or can be distilled from petroleum.

LDPE vs HDPE: Properties, Production and Applications

Polyethylene PE , light, versatile synthetic resin made from the polymerization of ethylene. Polyethylene is a member of the important family of polyolefin resins.

It is the most widely used plastic in the world, being made into products ranging from clear food wrap and shopping bags to detergent bottles and automobile fuel tanks. It can also be slit or spun into synthetic fibres or modified to take on the elastic properties of a rubber.

Ethylene C 2 H 4 is a gaseous hydrocarbon commonly produced by the cracking of ethane , which in turn is a major constituent of natural gas or can be distilled from petroleum. Under the influence of polymerization catalysts, the double bond can be broken and the resultant extra single bond used to link to a carbon atom in another ethylene molecule.

Thus, made into the repeating unit of a large, polymeric multiple-unit molecule, ethylene has the following chemical structure:. This simple structure, repeated thousands of times in a single molecule, is the key to the properties of polyethylene. The long, chainlike molecules, in which hydrogen atoms are connected to a carbon backbone, can be produced in linear or branched forms. The basic polyethylene composition can be modified by the inclusion of other elements or chemical groups, as in the case of chlorinated and chlorosulfonated polyethylene.

In addition, ethylene can be copolymerized with other monomers such as vinyl acetate or propylene to produce a number of ethylene copolymers. All of these variants are described below. ICI during studies of the effects of extremely high pressures on the polymerization of polyethylene. ICI was granted a patent on its process in and began commercial production in It was first used during World War II as an insulator for radar cables.

The process was later improved by the Italian chemist Giulio Natta , and the compounds are now known as Ziegler-Natta catalysts. In part for this innovation , Ziegler was awarded the Nobel Prize for Chemistry in Since that time, by using different catalysts and polymerization methods, scientists have produced polyethylene with various properties and structures. These processes yield a polymer structure with both long and short branches.

Because the branches prevent the polyethylene molecules from packing closely together in hard, stiff, crystalline arrangements, LDPE is a very flexible material. Principal uses are in packaging film, trash and grocery bags, agricultural mulch, wire and cable insulation, squeeze bottles, toys, and housewares.

The plastic recycling code of LDPE is 4. It is made by copolymerizing ethylene with 1-butene and smaller amounts of 1-hexene and 1-octene, using Ziegler-Natta or metallocene catalysts. The resultant structure has a linear backbone, but it has short, uniform branches that, like the longer branches of LDPE, prevent the polymer chains from packing closely together. HDPE is manufactured at low temperatures and pressures, using Ziegler-Natta and metallocene catalysts or activated chromium oxide known as a Phillips catalyst.

The lack of branches in its structure allows the polymer chains to pack closely together, resulting in a dense, highly crystalline material of high strength and moderate stiffness. Products include blow-molded bottles for milk and household cleaners; blow-extruded grocery bags, construction film, and agricultural mulch; and injection-molded pails, caps, appliance housings, and toys.

The plastic recycling code number of HDPE is 2. Linear polyethylene can be produced in ultrahigh-molecular-weight versions, with molecular weights of 3,, to 6,, atomic units, as opposed to , atomic units for HDPE. These polymers can be spun into fibres and then drawn, or stretched, into a highly crystalline state, resulting in high stiffness and a tensile strength many times that of steel.

Yarns made from these fibres are woven into bulletproof vests. Ethylene can be copolymerized with a number of other compounds. Ethylene-vinyl acetate copolymer EVA , for instance, is produced by the copolymerization of ethylene and vinyl acetate under pressure, using free-radical catalysts.

Many different grades are manufactured, with the vinyl acetate content varying from 5 to 50 percent by weight. EVA copolymers are more permeable to gases and moisture than polyethylene, but they are less crystalline and more transparent, and they exhibit better oil and grease resistance.

Principal uses are in packaging film, adhesives, toys, tubing, gaskets, wire coatings, drum liners, and carpet backing. Ethylene-acrylic acid and ethylene-methacrylic acid copolymers are prepared by suspension or emulsion polymerization, using free-radical catalysts.

The acrylic acid and methacrylic acid repeating units, making up 5 to 20 percent of the copolymers, have the following structures:. The acidic carboxyl CO 2 H groups in these units are neutralized with bases to form highly polar ionic groups distributed along the polyethylene chains. Ionic polymers of this type are called ionomers. The ethylene-acrylic acid and ethylene-methacrylic acid ionomers are transparent, semicrystalline, and impervious to moisture. They are employed in automotive parts, packaging film, footwear, surface coatings, and carpet backing.

One prominent ethylene-methacrylic acid copolymer is Surlyn, which is made into hard, tough, abrasion-resistant golf-ball covers. Other important ethylene copolymers are the ethylene-propylene copolymers. Polyethylene Article Media Additional Info. Article Contents. Home Science Chemistry Polyethylene chemical compound. Print print Print. Table Of Contents.

While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Facebook Twitter. Give Feedback External Websites. Let us know if you have suggestions to improve this article requires login.

External Websites. Polymer Science Learning Center - Polyethylene. The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree See Article History.

Alternative Titles: PE, polyethene, polythene. Read More on This Topic. Ethylene, commonly produced by the cracking of ethane gas, forms the basis for the largest single class of plastics, the polyethylenes Get a Britannica Premium subscription and gain access to exclusive content. Subscribe Now. The branched form of polyethylene, known as low-density polyethylene LDPE. The linear form of polyethylene, known as high-density polyethylene HDPE. Learn More in these related Britannica articles:.

Ethylene, commonly produced by the cracking of ethane gas, forms the basis for the largest single class of plastics, the polyethylenes. Between and , Ziegler and Hans-Georg Gellert, one of his former students from Halle, found that in the polymerization reaction organolithium compounds, except for lithium aluminum hydride, irreversibly decomposed into lithium hydride and an alkyl.

To establish whether lithium or aluminum was the…. Unless hydrogen bonds are present in which case molecular solids resemble ionic solids in brittleness , molecular solids are generally soft and have low melting points because the bonds between the molecules are easily overcome. History at your fingertips. Sign up here to see what happened On This Day , every day in your inbox!

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Polyethylene Maufacturing and its Properties

Both materials derive from polyethylene PE , which is the most popular plastic in the world, used in everything from supermarket bags to bullet-proof vests. PE is a thermoplastic created by polymerising ethylene. In other words, these polymers have different properties because of the structure of their molecules. Picture a single, straight line — a chain — of molecules. Within this line another chain branches off in one direction. From that chain another chain branches off.


PDF | This book bridges the meaning of engineering end-use parameters of polyethylene resins (HDPE, LDPE, LLDPE, VLDPE) and their.


Polyethylene

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High-density polyethylene or HDPE is a commonly used petroleum thermoplastic and the most used of the three polyethylenes for a wide range of applications.

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