WHAT IS POLYETHYLENE

WHAT IS POLYETHYLENE

Polythene resins are milky white, translucent substances derived from ethylene (CH2=CH2). Its chemical formula is [─CH2─CH2─]n (where n denotes that the chemical formula inside the brackets repeats itself to form the long chains of plastic molecules).

n CH2=CH2  [─CH2─CH2─]n

When Hogan and Banks first created a reaction between ethylene and benzaldehyde using two thousand atmospheres of internal pressure, their experiment went askew when all the pressure escaped due to a leak in the testing container. On opening the tube, they were stunned to find a white waxy substance that looked a lot like some form of plastic. After repeating the experiment, they discovered that the loss of pressure was not due to a leak at all, but was a result of the polymerization process. The residue polyethylene (PE) resin was a milky white, translucent substance derived from ethylene (CH2=CH2). Polyethylene was produced with either a low or a high density.

Low-density polyethylene (LDPE) has a density ranging from 0.91 to 0.93 g/cm3 (0.60 to 0.61 oz/cu in). The molecules of LDPE have a carbon backbone with side groups of four to six carbon atoms attached randomly along the main backbone. LDPE is the most widely used of all plastics, because it is inexpensive, flexible, extremely tough, and chemical-resistant. LDPE is molded into bottles, garment bags, frozen food packages, and plastic toys.

High-density polyethylene (HDPE) has a density that ranges from 0.94 to 0.97 g/cm3 (0.62 to 0.64 oz/cu in). Its molecules have an extremely long carbon backbone with no side groups. As a result, these molecules align into more compact arrangements, accounting for the higher density of HDPE. is stiffer, stronger, and less translucent than low-density polyethylene. HDPE is formed into grocery bags, car fuel tanks, packaging, and, of course, piping.

 POLYETHYLENE PIPE

The history of the polyethylene (PE) pipe begins with early civilization's attempts to find a suitable transport medium that could move water and other fluids from one place to another. It is no secret that plastic is relatively a new kid on the block as a piping material. Concrete has, in some form or another, been around since the Assyrians, Babylonians and Egyptians, while steel was first patented in 1855. Plastic piping, on the other hand, beginning with polyvinyl chloride or PVC in 1926, dates back to the 1930s, when it was utilized for sanitary drainage. Polyethylene was first developed in 1933 as a flexible, low-density coating and insulating material for electrical cables. It played a key role during World War II -- first as an underwater cable coating and then as a critical insulating material for such vital military applications as radar insulations. Because of its lightweight, radar equipment was easier to carry on a plane, which allowed the out-numbered Allied aircraft to detect German bombers under difficult conditions such as nightfall and thunderstorms.

POLYETHYLENE TIME LINE

1862 - Parkesine, the first synthetic plastic

1866 - Celluloid by John Wesley Hyatt

1891 - Rayon is used to make Cellophane

1900 - Celluloid is used for Film

1907 - Bakelite, the first thermosetting synthetic resin.

1918 - Polystyrene

1926 - PVC or Polyvinyl Acetate

1927 - Nylon - synthetic silk for stockings in 1939

1933 - Polyethylene

1935 - Low Density Polyethylene

1938 - Teflon

1951 - High Density Polyethylene

1957 - Velcro and Silly Putty