3 HDPE.

The invention of the low-pressure process to make HDPE took place in both the U.S. and Europe at nearly the same time and centered around the development of types of catalysts that promoted ethylene polymerization at milder temperatures and pressures than were (and still are) used for LDPE.

The first of these new catalysts was discovered in 1951 by Robert Banks and John Hogan at Phillips Petroleum (who were also pioneers in PP polymerization). In 1953, Prof. Karl Ziegler at Germany's Max Plank Institute for Coal Chemistry developed another low-pressure/low-temperature catalyst system. By the late 1950s, both methods were being used for HDPE production. In Europe, the first hill-scale low pressure HDPE plant was erected by Farbwerke Hoechst AG in late 1955. PLASTICS TECHNOLOGY reported in September 1955 that Hoechst's Hostalen resin, with a density of 0.94 g/cc, was the talk of the Hanover Industrial Fair in Germany, where it was shown for the first time in applications such as film, pipe, tubing, and molded household articles.

In the U.S., Phillips produced the first commercial HDPE (0.963 density) under the Marlex tradename in the summer of 1956, although it had provided pilot plant quantities as early as 1955. At NPE 1958, commercial HDPE resins were featured by Celanese, Phillips, Spencer Chemical (marketing for Exxon), and W.R. Grace. These suppliers highlighted the potential of blow molded rigid HDPE for replacing glass containers. Other early suppliers to follow included Hercules, Koppers, and Dow.

Among the earliest products were extrusion blow molded bottles for bleach and detergents, baby bottles, and injection molded housewares, such as the famous Tupperware containers.

One of the largest volume applications emerged in an unexpected way in 1957, when the Hula Hoop, an extruded tube bent into a circle, became a fad among teenagers throughout the U.S. and abroad. Wham-O, which trademarked the Hula Hoop name and was its most successful manufacturer, produced the toy using Phillip's Marlex HDPE. It was this fad that led to large-volume manufacturing of extruded HDPE pipe for high-performance applications such as natural-gas distribution, handling mine railings, and sewer lines.

Use of blow molded HDPE bottles grew far beyond detergents and bleach to include shampoos, motor oil, drug and cosmetic products, water, and milk. Milk bottles, in fact, are the single biggest volume HDPE package. Other large-volume applications are ice chests, beverage coolers, jerry cans, trash cans, storage drums, auto fuel tanks, injection molded food containers (e.g., for margarine and yogurt), and wire/cable coatings--including transoceanic cables.

Meanwhile, high-molecular-weight (HMW) HDPE made its impact in the film market a bit later. In 1979, Sonoco tested the shopping/grocery bag potential of HMW-HDPE. At NPE '88, HDPE blown film lines were a highlight.

The American Plastics Council (APC) figures North American HDPE consumption in 2004 at 15.264 billion lb, making it the second-largest volume commodity thermoplastic after PP.