Virgin HDPE
Virgin HDPE is the pure and freshly made form of HDPE. Unlike scrap HDPE, which has been used for various applications prior to being recycled, Virgin HDPE has never been used for any applications whatsoever. It can easily be recognized by the translucent quality of the pellets or granules, and is regarded as being the most pure and highest quality HDPE product available on the market.
Why Use Virgin HDPE?
Virgin HDPE is an excellent material to use if one is looking to produce brightly colored products, as unlike scrap HDPE, which has generally been contaminated and colored, and so results in murky tones, virgin HDPE takes color well, and the results of coloring virgin HDPE are generally bright, vibrant tones, perfect for children’s toys.
Other advantages over scrap HDPE include the fact that virgin HDPE is a contaminant free source of HDPE. Scrap HDPE is often contaminated with various metals, other plastics, dyes, labels, dirt, and other elements which degrade the quality of the HDPE. Whilst great care is usually taken to cleanse scrap HDPE of these contaminants, it is simply impossible to produce entirely contaminant free scrap HDPE at this stage.
Virgin HDPE is also structurally sounder than scrap HDPE, which has been heated and molded at least once before in its life, and therefore has undergone some weakening on a molecular level. With each subsequent heating and molding, HDPE looses some of its strength and structure. Imagine it like a plastic rod that is held between the hands and bent one way and then the other. It remains intact on the first bending, but with each subsequent bending, the stresses on the material cause it to strain and then to snap entirely. It is the same with the molecular bonds in HDPE. If you wish to produce top of the line HDPE products, or if strength is a priority in your product design, then it is advisable to make use of virgin HDPE.
Virgin HDPE is also required if one wishes to manufacture products that will come in contact with food stuffs, such as milk bottles, cereal packet liners, margarine tubs, or any other product which will be used to package food. Scrap HDPE is not approved for food contact applications due to the contamination which is invariably present in scrap HDPE.
The Process Of Making Virgin HDPE
HDPE starts out life as naphtha, a substance which is extracted from crude oil, the same oil which is used to make gasoline, diesel, propane, and other plastics. In order to make ethylene, the naphtha is “cracked”, which means that it is heated to very high temperatures to the point where its chemical and molecular bonds start breaking down, and ethylene gas is released.
Once the ethylene is released, it can be transformed into HDPE via one of the following processes:
- Phillips Catalyst Slurry Process
- Ziegler Catalyst Solution Process / Slurry Process
- Gas Phase Reaction
The Phillips Catalyst slurry process is the most popular form of HDPE production, closely followed by the Ziegler Catalyst process. In both cases, ethylene is exposed to a catalyst which promotes polymerization, which is the linking of molecules to form larger compounds. Polyethane is simply a compound composed of many ethylene molecules strung together, hence the term “poly” (the Greek word for many) is used in front of the chemical name ethylene, to indicate that the compound is made from many ethylene molecules linked together. These processes make not only HDPE, but also MDPE (medium density polyethylene) and LDPE (low density polyethylene.)
When polyethylene was first created, it was done so at extremely high pressure, equivalent to several hundred atmospheres. However it is not practical nor economical to manufacture HDPE under these conditions, so catalysts are used to lower the pressure at which polymerization will take place. Catalysts are agents that help reactions to occur more quickly, but do not become mixed with the final product. The Phillips catalyst is chromium trioxide based, while the Ziegler catalyst is based on titanium halides and organoaluminium compounds. The Ziegler catalyst works at lower temperatures and pressures than the Phillips, and so is more economical to use, however both catalytic methods are in common use in the production of virgin HDPE today.
In either case, the result of the catalytic reaction is a translucent liquid, pure virgin HDPE. The catalytic process involves heating and high pressures to create the HDPE, but once the process is complete, and the temperature of the newly made HDPE begins to fall, then it starts to solidify. Before it becomes a solid, the liquid HDPE is extruded through a die and cut into the milky white granules or pellets that are purchased by the manufacturers of HDPE products world wide.
Supplier of Virgin HDPE Granules
We supply both virgin and recycled HDPE granules from sources all over the world. Please contact us through the form below and let us know your detailed requirements. We will get back to you with a quote shortly