Polyethylene is made from the polymerization of ethylene (or ethene) monomer. Polyethylene chemical formula is (C2H4)n.
Polyethylene is a lightweight, durable thermoplastic with variable crystalline structure. It is one of the most widely produced plastics in the world (tens of millions of tons are produced worldwide each year). Polyethylene is used in applications ranging for films, tubes, plastic parts, laminates, etc. in several markets (packaging, automotive, electrical, etc.).
The commercial process (the Ziegler-Natta catalysts) that made PE such a success was developed in the 1950s by two scientists, Karl Ziegler of Germany and Giulio Natta of Italy.
What is HDPE ( High Density Polyethylene ) :
HDPE ( High Density Polyethylene ) is a robust, moderately stiff plastic with a highlypolyethylene-hdpe-trashcan-1 crystalline structure. It is frequently used in plastic for milk cartons, laundry detergent, garbage bins, and cutting boards.
HDPE is produced majorly using two techniques: Slurry Polymerization or Gas Phase Polymerization . High density polyethylene is flexible, translucent/waxy, weather resistant, and displays toughness at very low temperatures .
Density : 0.941-0.965 g/cm3
Crystallinity : High crystalline and low amorphous (>90% crystalline)
Characteristics : Excellent Chemical Resistance , High tensile strength , Excellent moisture barrier properties , Hard to semi-flexible .
General Applications Of High Density Polyethylene :
Molecular weight distribution is relatively narrow, has applications in injection moldings or flat yarns, and the latter type . Molecular weight distribution is wide, is used to make film products, hollow plastic products and pipes .
What Is LDPE ( Low Density Polyethylene ) :
Low-Density Polyethylene (LDPE) is a very flexible material with unique flow properties that makes it particularly suitable for shopping bags and other plastic film applications. LDPE has high ductility but low tensile strength, which is evident in the real world by its propensity to stretch when strained .
Two basic processes used for the production of low density polyethylene: stirred autoclave or tubular routes. The tubular reactor has been gaining preference over the autoclave route due to its higher ethylene conversion rates .
Density : 0.910-0.925 g/cm3
Crystallinity : Low crystalline and high amorphous (less than 50-60% crystalline)
Characteristics : Flexible and good transparency , Good moisture barrier properties , High impact strength at low temperature , Excellent resistance to acids, bases and vegetable oils .
General Applications of Low Density Polyethylene (LDPE) :
Shrink wrap, films, squeezable bottles garbage bags, extrusion moldings, and laminates
What is LLDPE ( Linear Low Density Polyethylene ) :
LLDPE is produced by polymerization of ethylene (or ethane monomer) with 1-butene and smaller amounts of 1-hexene and 1-octene, using Ziegler-Natta or metallocene catalysts. It is structurally similar to LDPE .
The structure of LLDPE has a linear backbone with short, uniform branches (unlike longer branches of LDPE). These short branches are able slide against each other upon elongation without becoming entangled like LPDE .
In the present day scenario, Linear low density polyethylene (LLDPE) has been quite successful in replacing Low Density Polyethylene .
Density : 0.91-0.94 g/cm3
Crystallinity : Semi-crytalline, level between 35 to 60%
Characteristics : As compared to LDPE, it has : Higher tensile strength , higher impact and puncture resistance .
General Applications of LLDPE : High performance bags, cushioning films, tire separator films, industrial liners, elastic films, ice bags, bags for supplemental packaging and garbage bags .
PE, polyurethanes and PVC are widely used thermoplastics for agricultural pipes, tubing, hose pipes and for creating custom pipe solutions. Although no plastic tubing product can universally handle all applications, and there are certain differences that need to be considered per application area .
As compared to PU, polyethylene is less flexible but offers good moisture resistance. Polyurethane pipes are used where flexibility, kink resistance along with exceptional abrasion resistance is needed like cable jacketing, pneumatic controls, analytical instrumentation, etc. Whereas, polyethylene pipes exhibit high strength, good corrosion- and chemical resistance & hence suitable for use in municipal, industrial, marine, mining, landfill, duct and agricultural applications .
While, flexible PVC has several benefits like good chemical and corrosion resistance, excellent abrasion and wear resistance, rubber-like flexibility, visual contact with the flow (with clear styles), and outstanding flow characteristics. These properties enable PVC tubing use in general industrial, food and beverage, potable water lines, medical, chemicals, fuels, oils, and mechanical applications .