What is Marlex and what is it used for? - EngineeringClicks (2024)

• May 30, 2017
• Mark Benson

Like so many of the most influential feats of industry the vast majority of us will have no idea what Marlex is, what it does and the fact it is all around us. While the discovery itself dates back to 1951 with the Phillips Petroleum Company the foundations for this actually date back to 1925. This was an era in which the polymer industry was relatively under developed (and underfunded) and while new materials were being discovered on a regular basis few have been as influential and useful as Marlex.

Over the years there were three different patent applications for what we now know as Marlex and after a three decade battle J Paul Horgan and Robert L Banks, employees of the Phillips Petroleum Company in Oklahoma, were recognised as the original patent holders. Unbeknown to them their discovery created a multibillion-dollar business which has had a significant impact upon our everyday lives.

What is Marlex?

In simple terms Marlex is the trade name for crystalline polypropylene and high-density polyethylene (HDPE) which is a solid polymer created using ethylene and propylene – with a vital catalyst. Crystalline polypropylene and polyethylene are components of natural gas created in the refining process. Hogan and Banks were given the task of finding ways to utilise individual components of natural gas and in June 1951 they had their Eureka moment.

Their original experiment saw nickel oxide used as a catalyst to convert polypropylene and ethylene into a more workable material – in liquid form. The ground breaking moment occurred when a small amount of chromium oxide was introduced into the mix. The nickel oxide created a liquid but the chromium oxide created a solid white material which was unexpected to say the least. The next step was to remove the nickel oxide from the catalyst leaving the chromium oxide to convert the polypropylene and ethylene to this new solid white material.

Main benefits of Marlex

It is the high-density element of the polyethylene (HDPE) which sets it apart from the low-density polymers created by ICI in the 1930s. The ICI manufacturing process required 20,000 to 30,000 pounds of pressure per square inch and only created a low-density material. Hogan and Banks created a process which required just a few hundred pounds of pressure per square inch and created a high-density material which was heat resistant, extremely hard and rigid. Surely this would be the next big thing in the world of polymers?

How do you market a new polymer?

In 1954 Phillips introduced HDPE under the brand name Marlex polyethylene expecting to hit the big time and dominate the plastics industry for years to come. Like so many companies which are “first to market” with groundbreaking technology, things did not go smoothly in the early years. Demand for this type of material had expanded rapidly between initial discovery and full-blown marketing in 1954. Unfortunately Phillips had initially misunderstood the market producing only one grade of HDPE which was not compatible with many applications. As the unsold stock began to pile up in the warehouse things took an unexpected turn!

During the 1950s the “hula hoop” became the must have toy in the US and eventually around the world. Yes you have guessed it, Marlex polyethylene (HDPE) was the perfect material for the hula hoop and overnight the company was struggling to keep up with demand. This unexpected windfall allowed Phillips to concentrate on creating different graded Marlex behind the scenes while the hula hoop craze effectively kept the business going.

Common uses of Marlex

Polypropylene and high-density (HDPE) are used in many different areas of everyday life including everything from battery cases to fuel tanks, pipes to toys, medical equipment to everyday plastic bottles. This is only a fraction of the everyday use of Marlex, a material “found by accident” in 1951 even though the discovery process can be traced back to 1925. This product revolutionised the Phillips Company and just goes to show that the harder you try the luckier you are.

Thinking outside the box created a product which many people have never heard of but could not be without today.