We represent a good number of companies who are in constant need of raw plastic material in all forms (everything ranging from scrap to virgin grade granules). To be able to supply our clients we have formed good, ongoing business relations with HDPE manufacturers whose product we find to have the best quality at sound prices.

Please contact us through this form below and include your detailed requirements. We will reply shortly and offer some solutions.

HDPE Granules

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The Making Of HDPE Resin

HDPE resin is produced by a process called polymerization.. Polyethylene is polymerized from ethylene gas, and HDPE is a high density form of this substance, which possesses a very linear chemical structure. The linear structure of this compound makes it not only very dense, but also very strong and fairly chemically resistant. HDPE resin is generally referred to as being inert, which gives it an advantage over many other substances commonly used in various types of commercial applications, which become weakened when exposed to various types of chemicals.

It may surprise you to know that HDPE resin actually begins life as crude oil. From crude oil, a substance called naphtha is extracted by means of distillation. Naphtha is itself a carcinogen, and a very powerful substance used in a wide range of petrochemical applications. To make HDPE resin, naphtha is ‘cracked’, a term which refers to heating it at very high temperatures until it releases ethylene gas.

This ethylene gas is then exposed to a catalyst at high pressure and temperature. The combination of the temperature, pressure, and the catalyst (a substance that helps reactions take place more quickly and easily than they would naturally), forces the ethylene molecules to join together in long chains. The resulting substance is polyethylene.

By changing various elements of the reaction, varying types of polyethylene can be produced. When HDPE resin is first produced, it is a sticky viscous mass with a whitish, translucent, opaque color. Most producers will take this HDPE resin and extrude it through a die, and cut it into small pellets before letting it cool into its solid state.

HDPE resins are also available in reprocessed form. Reprocessed HDPE is made from scrap HDPE, which is gathered from both households and industrial sources. Most HDPE collected from people’s homes is known as post consumer scrap HDPE, whereas HDPE collected from industrial sources is known as post industrial scrap HDPE. One of the extremely useful qualities of HDPE resin is the way that it is able to be easily melted down and formed into new products.

Reprocessed HDPE resins may have small amounts of contamination in them, due to the exposure they have had to contaminants in their prior uses, but every care is taken to try and ensure that reprocessed HDPE resins are as clean as they can possibly be. Some forms of scrap HDPE resin are simply washed and shredded loads of HDPE. These may contain a good deal of contaminants, as not all can be removed just by washing. Some potential contaminants in shredded HDPE resin include labels, other plastics, and sometimes even small pieces of metal. Reprocessed HDPE pellets are much cleaner however, as they are produced from melting down the shredded HDPE and filtering it thoroughly before it is made into pellets.

Properties of HDPE Resins

HDPE resin is a very interesting and unique type of plastic resin. It is regarded as being chemically inert, which means that it makes good containers for many different types of chemicals. It also has a PH resistance from PH 1.5 to PH 14, which makes it suitable for carrying and transporting acids and bases. HDPE resins also demonstrate a fairly wide temperature tolerance, being able to maintain molecular structure in temperatures as low as 148 degrees Fahrenheit, and as high as 248 degrees Fahrenheit. HDPE has an average tensile strength of around 4550 psi, and when under pressure, will bend to accommodate pressure long before it cracks.

HDPE Resin Applications

HDPE resins come in a wide range of grades for various applications. HDPE resins can be formed into bottles, blown into film, made into pipes, or injection molded to make irregularly shaped objects and toys. HDPE resins are found in all areas of daily life, most people now have several products in their homes made of HDPE resins. Shampoo bottles, garden furniture, the piping running under your home, all these things can be made of HDPE resin. HDPE resin is also used in a wide range of commercial applications, from containers, to pipes, to parts for various mechanical processes. With such a wide range of applications, there are also a wide range of types of HDPE available to the manufacturer.. These types of HDPE resins are classified into grades, which are in turn, distinguished by the purpose the grade fits

HDPE Resin Grades

Blow Molding Grade HDPE Resin – Blow molding grade HDPE resin is quite viscous. Blow molding applications require that the HDPE be quite thick and flow slowly, because blow molding involves the HDPE being blown up into the shape of a mold with compressed air. HDPE resin that is too runny would simply gather at the bottom of the mold and produce very badly deformed products.

Injection Molding Grade HDPE Resin – Just the opposite of blow molding grade resin, injection molding grade HDPE resin must be very runny so that it can be quickly injected into a mold, cooled, and then ejected. Injection molding is often used to make items with odd shapes, so an HDPE resin that flows freely into every nook and crevice is essential.

Film Grade HDPE Resin – Film Grade HDPE Resin falls somewhere between injection molding grade HDPE resin and blow molding grade HDPE resin. This is a semi viscous HDPE resin, strong enough to stand being blown into a thin film for carrier bags and other film applications.

Pipe Grade HDPE Resin – Pipe grade HDPE resin is a very strong, dense resin that can stand up to the wear and tear that pipes are exposed to. HDPE pipes are often used both underground and underwater, and sometimes must carry a great deal of weight on top of them. Pipe grade HDPE resin stands up to this task, and produces high quality pipes that stand the test of time.

Off Grade HDPE Resin – Off grade HDPE resin is a type of HDPE resin that does not fall into any particular grade. This resin is typically produced when an HDPE resin production line switches from making one grade of resin to another. The resin produced in the in between stage generally does not have the characteristics of either the resin that was originally produced, or the resin that is being subsequently produced. This resin is not suitable for high intensity applications, but is still useful for applications where high end resin is not necessary. For example, if HDPE pipes were being made to go underneath a road, one would definitely want to be using high quality HDPE pipe grade resin, however, if one is simply making a shampoo bottle inner, it is not necessary to have the highest quality material, as the product will not need to operate under extreme conditions.

For further information on HDPE resins, please refer to the other articles on the site.

HDPE Granules

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Off Grade HDPE is HDPE which does not meet the specifications for any HDPE Grade. Due to this fact it is not recommended for manufacturers who require a high level of performance from their HDPE. However, for many manufacturers who do not require an extremely high grade product, off grade HDPE can be a better option than purchasing the more expensive prime HDPE. For instance, some off grade HDPE may lack the tensile strength of prime grade HDPE. However, if your application is a lightweight bottle, this may not make any discernible difference to the quality of the end product.

How Is Off Grade HDPE Produced?

Off grade HDPE can result from faulty polymerization settings, or it may be a by product of a successful production of prime HDPE. Most often, off grade HDPE is produced when production is switched from one grade of HDPE to another. Take for example, an HDPE production plant where injection molding grade HDPE, which has a very low viscosity, is being produced. If production is then changed to, say, blow molding grade HDPE, which has a very high viscosity, then there is often a period and a few production runs in which the processes are tweaked and changed, and in which the resulting HDPE is not prime grade for either usage. This HDPE is off grade HDPE, and while not suitable for high stress blow molding or injection molding, it may still be useful in other applications.

What Isn’t Off Grade HDPE?

When searching for off grade HDPE, one has to keep one’s wits about one. Some unscrupulous purveyors sell contaminated reprocessed HDPE as “off grade”. However, this is not off grade HDPE, this is merely low quality HDPE, and is quite a different proposition altogether. Contaminated HDPE should be avoided, as it can cause defects in final products, and may not even be able to undergo processing and molding at all.

Off grade HDPE is simply HDPE that does not fall into defined HDPE grades, for instance Pipe Grade, or Injection Molding Grade, as was already mentioned. Off grade HDPE still retains its structural integrity, and is still a quality product, if not entirely suitable for highly demanding applications.

Off grade HDPE can come from virgin HDPE or reprocessed HDPE, off grade virgin HDPE is generally the “safest” form of off grade HDPE to purchase, but reprocessed off grade HDPE is also a decent source of HDPE if purchased from a reputable purveyor.

The reason why it is so important to purchase from an experienced and reputable HDPE seller, especially when it comes to reprocessed HDPE products, is the fact that scrap HDPE can easily be ruined if it is not handled well during reprocessing. Reprocessed HDPE has not only been exposed to contaminants during its life, so great care must be taken in the washing and filtration stages of reprocessing, but it has also been exposed to several heat cycles, and with every heat cycle it is more and more likely that the molecular structure of the HDPE will break down, and that the resulting HDPE will be of poor quality. If the HDPE is handled correctly however, these issues will not arise, and manufacturers can feel confident using reprocessed off grade HDPE in their products.

The other factor to take into account is the fact that reprocessed HDPE generally lacks the clean translucent white color of virgin HDPE, due to the fact that it has generally been exposed to dyes either in its previous product incarnation, or during reprocessing colors from other items of HDPE have leeched into the HDPE stream. There are some exceptions to this rule, but much reprocessed HDPE will be colored in some way. This is not important for some applications, but if you are looking to produce a product that is appealing to the eye, then off grade reprocessed HDPE may not be the best choice.

Conclusion

Purchasing off grade HDPE does not mean purchasing unsound or contaminated HDPE. Purchasing off grade HDPE means purchasing a low cost, quality source of HDPE that will keep material costs down whilst still producing a quality end product.

If you wish to buy this type of HDPE or any other type, please contact us.

HDPE Granules

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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

HDPE Granules

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The ‘grade’ of HDPE actually refers to a measurement known as Melt Flow Index, or MFI. The MFI is simply a measure of how fast or slow a HDPE product flows when melted, how viscous it is. MFI is inversely related to the molecular density of the HDPE. The more dense the HDPE, the lower the melt flow index, ie, the slower it flows when melted.

For injection molding applications, a high MFI is required, as it is essential that the HDPE flows quickly into the mold and fills every nook and cranny. In blow molding applications, a thicker, slower, and more gravity resistant HDPE product is required in order that the HDPE will retain its shape and a uniform thickness during the blow molding process.

Meet The HDPE Grades

There are three main grades of HDPE, listed in order of molecular density from highest to lowest, and therefore also in reverse order of melt flow index, from lowest to highest.

Blow Molding Grade HDPE

In blow molding, HDPE flows into a mold and is then blown up into shape with compressed air, not unlike a ballon. As the HDPE expands, it conforms to the shape of the mold. When the HDPE has finished expanding, and has cooled it is ejected as the finished product. This method is generally used for bottles and other products where strength is needed.

Film Grade HDPE

HDPE film is often made by melted HDPE being blown through a mold with compressed air, rising into a column of film. The film is then flattened and rolled up, ready to be processed into things such as carrier bags for groceries and the like.

Injection Molding Grade HDPE

In injection molding, HDPE flows into a cooled die through many small holes, quickly filling up the mold before cooling and being ejected as the finished product. Injection molding is suitable for a wide range of applications, including children’s toys and other products of irregular shape.

How Useful Are Grades?

It is worth noting that there are very few set standards when it comes to HDPE gradings. There is no absolute authority on the subject, and whilst grade may give an indication of suitability for various manufacturing applications, it is certainly not the only element that should be given attention when purchasing HDPE in virgin or scrap form.

It is also worth noting that grade is not a static value. Blow molding grade HDPE is not destined to forever remain blow molding grade HDPE. Through a process of blending HDPE with other grades, or even with LDPE, or perhaps other plastics or agents, the grade of HDPE can be changed. There really is no hard and fast rule when it comes to grades, although they are useful as a rule of thumb. The best way to go about purchasing HDPE is to be aware of the MFI you require, and seek a product that best approximates it.

What cannot be changed as easily as the grade is the quality of the HDPE. You might have the perfect grade HDPE for your application, but there is little point in having a nicely flowing HDPE source for say, injection molding, if the resulting products are structurally unsound due to contaminants in the HDPE product. This is especially of concern for manufacturers using scrap HDPE, HDPE regrind, HDPE flake, or recycled HDPE pellets or granules. Scrap products always contain a risk of contamination, so the source of the product should be weighed carefully before large orders are made and an entire production line put at risk.

HDPE Granules

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HDPE Injection Grade

HDPE is an excellent material for a wide range of injection molding applications. Due to its chemical resistance and high strength, high quality products can be produced from HDPE using various types of injection molding.

To understand where injection grade HDPE comes from, and how to obtain the best quality HDPE for your purposes, some understanding of HDPE is necessary.

HDPE can come from one of two sources, and is either freshly made virgin HDPE, or recycled from scrap HDPE. HDPE can then be separated into various grades, largely differentiated by their molecular weight, or their melt flow index. Molecular weight refers to the density of the molecules in a compound, and how heavy they are, and melt flow index refers to the viscosity of HDPE, ie, how fast or slow it flows.

These two factors are inversely related, and HDPE with a higher molecular weight will therefore possess a lower melt flow index. Injection grade HDPE has a higher melt flow index and lower molecular weight than, say, the type of HDPE used for milk bottles, which is blow molded. A high melt flow index means that the HDPE flows more quickly and has a thinner consistency than other forms of HDPE.

As the majority of scrap HDPE comes from milk bottles, this can potentially present a problem for the manufacturer who wants to use scrap HDPE as a source for injection molding applications. Fortunately, melt flow index is not a static property, and with the correct blending, blow molding grade HDPE can be transformed into injection grade HDPE.

It is useful to know the methods by which blow molding grade HDPE is transformed into injection grade HDPE, as some of the additives may cause problems for certain manufacturing applications. In some cases, polypropylene is added to HDPE to lower the molecular weight, and in others, certain amounts of LDPE may be blended with HDPE to create a more viscous product.

Injection mold grade HDPE is suitable for the production of products such as children’s toys, wide mouthed containers, and any product that has an intricate shape. The quickly flowing nature of injection grade HDPE allows the HDPE to not only be easily molded into a wide range of shapes, but it is also able to be molded very quickly indeed, which saves the manufacturer money when it comes to labor costs, and allows more items to be produced with greater speed than other methods.

HDPE Injection Molding Parameters

HDPE is suitable for injection molding, generally to a minimum thickness of between .010 and .040 inches. .020 inches is considered to be the absolute minimum thickness that should be attempted. Thinner product walls are likely to result in faults and flaws, including buckling and cracks.

HDPE has a density of .941 to .959. It has a linear molecular structure, and it is highly crystalline. If this sort of language seems too technical, it is not important. What is necessary to be known is that these characteristics amount to a high strength product that can withstand higher temperatures than lower density polyethylene, are harder, and have a greater chemical resistance.

Injection Molding Process

The injection molding process is very simple. Raw material HDPE is generally purchased in refined pellet or granule form, and is then melted prior to injection molding. The actual injection molding involves the process of injecting the molten HDPE into a die which is permeated with many small holes, which allow the HDPE to flow in quickly. The die is then cooled, and the newly molded product is ejected from the die, and the process begins anew. This method allows for the quick and efficient production of a wide range of products from bottles, to garden furniture.

Virgin HDPE, Or Scrap HDPE?

If you are looking to produce products that are brightly colored, it is recommended that you purchase virgin injection grade HDPE. Recycled injection grade HDPE is, generally speaking, just as sound as virgin HDPE, but it is generally a murky color due to the various colors of HDPE blended in the recycling process. Recycled injection grade HDPE is recommended for applications where the products produced are to be black in color, or hidden away out of sight. There are however sources of scrap HDPE where scrap is sorted by colors. One can for example get HDPE made of pure white milk bottles scrap, or clear milk bottles scrap, etc. In that case HDPE made of scrap would be equal in all characteristics to Virgin HDPE.

An ideal mix for many manufacturers is a pellet or granule containing low amounts of recycled HDPE, and mostly made up of virgin HDPE. Recycled HDPE lowers the overall cost of the raw material, and brings an elevated tensile strength to the product, whilst the virgin HDPE ensures that the correct melt flow index is achieved without the blending of foreign plastics such as polypropylene.

If you are going to use recycled HDPE for injection molding applications, it is imperative that you obtain your injection grade HDPE from a reputable purveyor. There can be a large variance in quality between suppliers even when dealing with more simple scrap HDPE products, and due to the added blending that is required to create reliable injection grade HDPE, there is even more potential room for error. An inferior raw material will invariably translate to an inferior end product, so reputable and experienced purveyors are worth their weight in gold.

HDPE Granules

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What is HDPE?

HDPE is one of the seven major forms of plastics commonly used in manufacturing and production today. This article will give a brief overview of HDPE, its properties, and its applications, and demonstrate why scrap HDPE is often the best choice for manufacturers from the standpoint of both cost effective operations, and environmental responsibility.

So, what is this substance known as HDPE? Simply put, HDPE is a plastic with a special set of properties that make it remarkably useful for a wide range of applications. HDPE is an acronym for High Density Polyethylene, and it is a substance most commonly used in packaging, as well as other everyday applications. Like many plastics, HDPE is produced from petroleum. HDPE is a thermoplastic, which means that it melts into a liquid state when heat is applied, which makes it a great recyclable product. This site will deal extensively with scrap HDPE, which is, of course, recycled HDPE. Scrap HDPE has a wide variety of uses and applications, and manufacturers are encouraged to use scrap HDPE where possible in order to lessen the environmental impact that plastic production has.

HDPE is one of the more commonly found plastics, you’re probably familiar with it even if you haven’t heard of it before, because HDPE is the plastic that Tupperware is made out of. You will also find HDPE in plastic bags, water pipes, folding chairs, and plastic refillable bottles. HDPE resists chemicals well, and is a very effective barrier against moisture, which means that it can be used for the packaging of household chemicals, as well as foodstuffs. Not only is HDPE produced in solid blown form for packaging and suchlike, it is also often manufactured as a film, which can be found in product linings, and as packaging for various types of snack foods. In any given day, most of use probably make use of several different forms of HDPE without even knowing it.

An extraordinarily versatile product, it is easy to see why HDPE is in such high demand. It originated as a modification of Polyethylene, which was a plastic invented in 1898 by a German chemist named Hans von Pechmann. Like many scientific inventions and discoveries, polyethylene came about by accident whilst the scientist was heating diazomethane, a toxic explosive. It was then rediscovered in an industrial accident at ICI works in Northwich, England in 1933 when high pressure was applied to benzaldehyde and ethylene tainted with oxygen. Between 1951 and 1953, a range of processes for reliably creating large amounts of polyethylene were created by Robert Banks, Paul J. Hogan of Phillips Petroleum, and Karl Ziegler, another German chemist. Polyethylene has grown hugely in popularity since its invention, and it is now estimated that over 60,000 tonnes of it are produced annually.

HDPE is simply a denser form of polyethylene that is suited to many commercial uses because it remains a solid at room temperature, and is stronger than standard polyethylene. In order to make one kilogram of HDPE, about 1.75 kgs of oil is needed, however due to its high recyclability, HDPE can be used again and again. Because of its strength, products made of HDPE can be reused many times, and are popular with manufacturers and consumers alike.

HDPE Granules

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