HDPE:

A Complete Buyer’s Guide

WHAT IS

High-Density Polyethylene?

Known for its versatility, processability, low cost and recyclability, HDPE has gained considerable traction across a multitude of industries, making it one of the most widely used types of plastics today. However, its production only really took off in the US during the 1950s, when improvements in manufacturing processes dramatically reduced the cost of plastics production.

This helped pave the way for inexpensive mass production. HDPE has the simplest and most straightforward chemical structure of all plastic polymers, which makes it fairly easy to process into different items. These are becoming remarkably popular in various low-value applications, as well as for industrial purposes. HDPE exhibits attributes of flexibility, chemical resistance, toughness and non-conducting electrical properties.

From uses in packaging and pharmaceutical products to heavy-duty damp-proof sheaths for new buildings and pipes for irrigation, HDPE is regarded as the most versatile plastic material ever created and is also the most commonly recycled plastic available.

The History of Synthetic Polymers & The Birth of HDPE

Polyethylene was first discovered by accident in 1898 when German chemist, Hans Von Pechman, created it while investigating a particularly volatile chemical compound called diazomethane. Diazomethane itself was too unstable to be used in industrial applications, and it took another 35 years before the first industrially practical polyethylene synthesis was discovered, in 1933, by two English chemists – Reginald Gibson and Eric Fawcett.

Again, totally by accident, the pair discovered that when they applied extremely high pressure to a mixture of ethylene and benzaldehyde, a white, waxy material was produced. But, this was still not to be the beginning of the commercial production of polyethylene. It was only in the 1950s, upon the development of two separate catalysts that promoted polymerization at mild temperatures and pressures, that brought about the substance we know as HDPE today.

In 1951, a chromium trioxide-based catalyst was discovered at Phillips Petroleum in the US, and two years later another German chemist, Karl Ziegler, developed a catalytic system based on titanium halides and organoaluminium compounds that worked at even milder conditions than the Phillips catalyst.

Towards the end of the 1950s, both catalysts were being used in the production of HDPE; although the Ziegler catalyst was improved upon some years later with the incorporation of magnesium chloride. This lead to a further development when catalytic systems, based on soluble catalysts – the metallocenes – were reported in 1976. Both these catalytic systems became the basis for the range of resins that are found today, including those of LDPE and linear low-density polyethylene (LLDP).

The State of The HDPE Market

The global HDPE market in 2018 is in a healthy position for growth, and a continuing upward trend is forecast for the next five years.

Source: PlasticInsight

There is a growing need for greater sustainability in the use of building materials, and tackling environmental issues is becoming a more prevalent trend across major developed countries like Germany and the UK.Growing economies such as China and India will also see the HDPE market flourish, as these countries gear up for an increasing number of construction projects.

Countries in the Middle East and Africa are upcoming markets, with the demand in the production of packaging products and an increase in research and development (R&D) activities playing a major role in the continued growth of HDPE products worldwide. Despite there being a positive outlook for the HDPE market over the coming years, a growing concern is volatility in the price of raw materials.

The overall scarcity of petroleum-based byproducts has seen ethylene – a material used in the manufacturing of HDPE – go through significant price fluctuations. Innovation in the plastics field, due to new technological advancements, also pose a significant challenge for HDPE going forward.

Source: Platts

How is High-Density Polyethylene Made?

HDPE is a thermoplastic material that is composed of hydrogen and carbon atoms. These atoms are joined together to form high molecular weight products. The methane gas produced during the process is put under specific controlled conditions, which involves applying intense heat to the petroleum (This is some Walter White stuff we’ve got going on here!)

This process is known as cracking, which aids in creating ethylene gas. During the production of this gas, its molecules attach to form a polymer which produces polyethylene. This is accomplished by using metallocene and Ziegler-Natta catalysts, or with the use of activated chromium oxide, which is also known as the Philips catalyst.At this stage, the polyethylene comes off with a cloudy appearance.

However, after it is put through a series of molds, it forms into granules. Once the molding process is complete, you are left with a strong polymer material that has a variety of uses and applications in your home or business premises. This plastic lacks branches in its configuration, which enables the polymer chains to pack closely together.

In turn, their close proximity to each other results in a dense, extremely crystalline material that has high strength and moderate stiffness. HDPE has a melting point of between 120 – 180°C (248-356°F), which allows it to withstand repeated exposure of 120°C (248°F) so that it can be sterilized.

HDPE PROPERTIES

Key Advantages of HDPE

Lightweight, Flexible & Extremely Strong

The tensile strength of HDPE is what enables a milk bottle, weighing only a few ounces, to carry gallons of milk. Its flexibility is especially useful for bending pipes, and absorbing surge pressures or vibrations caused by movements and stresses in soil.

Corrosion & Chemical Resistant

Car makers produce fuel tanks made of HDPE, as the material does not require any special coatings and is compatible with all kinds of biofuels. Its chemical resistance to a wide range of reagents makes HDPE the perfect material for use in tailings pipelines, and treatment applications in mining operations.  

Impact Resistant

When dropped, HDPE bounces automatically making it resistant to impact. The classic example is dropping a toy truck, for example, down a flight of stairs.  

Durable & Weather Resistant

This plastic can last for several generations, without wearing out. A home with a plastic-lumber deck or balcony should be around to entertain several generations of inhabitants.

Rot, Mold, Mildew & Insect Resistant

This beneficial property makes HDPE great for the manufacture of underground pipes, and specifically those that deliver water. From a safety perspective, HDPE is the most universally applicable pipeline material on the market.

Highly Malleable

HDPE can be easily reshaped to the required specifications when forced into a mold under high heat and pressure. When the material has cooled down, the mold is opened and the plastic object is generally complete. In fact, the Greek word ‘plasticós’ translates directly as ‘to mold’.

WHAT ARE

Its Consumer Applications

• It is stronger than standard polyethylene, which makes it an effective barrier against moisture;
• It remains solid at room temperature;
• It resists rot, insects and other chemicals;
• It doesn’t create harmful emissions during production or when used by consumers; and
• It doesn’t leak toxins into the water or soil.

So what consumer products use HDPE?

HDPE is commonly used to make:

1. Plastic bags
2. Opaque juice, milk and water containers
3. Bleach, shampoo and detergent bottles
4. Dishes
5. Garbage bags
6. Yogurt and margarine tubs
7. Medicine bottles
8. Cereal-box liners

It is also be used in PEX piping, Tyvek insulation and plastic/wood composites. Other than plastic lumber and recycled plastic furniture, HDPE is used to manufacture garden and lawn products, crates, office products, automobile parts and buckets.  

WHICH INDUSTRIES

Make use of HDPE? (And Why?)

• reduce water loss;
• Increase UV stabilization, thereby cooling the soil and chasing away insects; and
• eliminate photosynthetically active radiation, thereby preventing weed growth.

Additionally, solid-wall HDPE pipes are widely used in agricultural applications such as irrigation, drainage and water supply. These kinds of pipes tend to be selected over others due to them being the least expensive option when comparing materials, installation costs and performance. In fact, the range of advantages that make the use of these products important to farmers include them being:

• lightweight, easy to handle and transport;
• available in a broad range of sizes;
• reliable, due to their corrosion-resistance and ability to withstand sodium (especially salty water);
• leak-free, tough and impact-resistant; and, of course,
• extremely flexible.

When it comes to livestock, HDPE recycled plastic boards make easy to install, durable and weather-proof enclosures, whether for cattle, hogs or horses.

Major benefits here include the material’s durability, the fact that it is easy to clean and also, a bonus, that it is corrosion proof. The boards will not shatter or crack upon impact; rust, rot or corrode from moisture; and a regular hose removes most dirt and debris.

Because quality is key, be sure that your supplier conforms to the Relevant Safety Specifications. This way, you’ll be able to rely on HDPE sheets from a safety perspective – not just in the ways mentioned above for the containment of hazardous chemicals, but also for their higher melting point – resulting in less likelihood of damage or the release of harmful chemicals at high temperatures.

HDPE sheets are lighter than other materials in their class which means less expense in terms of manpower or fuel in their transportation, and so are not to be overlooked by those making the purchasing decisions.

Available for virtually all building project types, from new construction to interior fit-outs and operation & maintenance, LEED provides a framework that project teams can apply to create healthy, highly efficient and cost-saving green buildings. A LEED certification is a globally recognized symbol of sustainability achievement. Because quality is key, be sure that your supplier conforms to the relevant safety specifications.

This way, you’ll be able to rely on HDPE sheets from a safety perspective – not just in the ways mentioned above for the containment of hazardous chemicals, but also for their higher melting point – resulting in less likelihood of damage or the release of harmful chemicals at high temperatures. HDPE sheets are lighter than other materials in their class which means less expense in terms of manpower or fuel in their transportation, and so are not to be overlooked by those making the purchasing decisions.

The advantages of HDPE in vehicles in comparison to metals and other materials are as follows:

• lower mass translates into a lower fuel consumption;
• being simpler and faster to manufacture cuts costs;
• repair of HDPE parts is easier and less expensive, often just requiring manual welding to repair marks and breaks;
• it shows fewer signs of wear and tear;
• pollutant emissions are reduced; and
• it can adopt attractive shapes and an extensive range of colours for all the bells and whistles expected by the drivers (pilots and yachtsmen!) of today.

The packaging industry continues to lead the way, in comparison to other sectors, in its use of HDPE; with the overall volume taken up by the packaging industry expected to reach 31.1% of the global volume produced by the close of 2023. Booming consumer goods sales across the world are causing the packaging industry to double up on its manufacturing processes, as well as on the consumption of raw materials – including that of HDPE.

WHAT ARE THE

Industrial Applications of HDPE?

HDPE Pipe

This is strong, durable, flexible and lightweight. When fused together, the different sections of piping offer a zero-leak rate and are more environmentally sustainable than other types of piping, due to being non-toxic, corrosion and chemical resistant, long lasting and suitable for trenchless installation methods. Indications that you’ve chosen a top-notch supplier include the following:

• the company can produce bulk orders;
• they have a good service record;
• they are hands-on in the development, research and production of HDPE, and possibly also of similar plastics like PVC, PPR, PP and PEX; and
• they allow a measure of flexibility on cost, but refrain from buying cheap.

A telling sign is the number of industries making use of HDPE piping, including:

• Civil engineering (for water mains, service pipes, sewer-reticulation systems and cables in electrical installations);
• Building and construction (in cold-water reticulation systems and house connections, as well as ducting for air-conditioning and refrigeration);
• Agriculture (irrigation in water-supply schemes and suction lines, plus for drainage and irrigation applications);
• Industrial (for domestic sewage systems and sanitary systems, plus the safe conveyance of chemicals or potable water);
• Mining (in both surface and underground operations and slurries); and lastly
• Marine/aquaculture (for supply lines and floats, and to facilitate trenchless technology).

For an in-depth look at HDPE Pipes you can follow this link to – HDPE Pipe A Complete Guide

One of the three major packaging applications of PETE, beside containers (bottles, jars and tubs) and semirigid sheets for thermoforming (trays and blisters), are the thin-oriented films currently being produced (bags and snack food wrappers). PEN, although more costly than PETE, provides better performance at high temperatures – allowing hot refills, rewashing and reuse. PEN also provides protection against the transfer of flavors and odors.  

HDPE Sheets

The beneficial properties of this material, i.e. its lightness, durability, chemical resistance and electrical properties, make it ideal for manufacturing wear strips and chain guides; fume cabinets, ducting and chemical tanks; vacuum forming and profile cutting; and automotive parts like mud flaps and dam linings.

Additionally, HDPE is used in the manufacturing of UV protective sheets and tarpaulins that offer high-quality weather protection. A typical application of HDPE plastic sheets is that of outdoor furniture, encompassing picnic tables and benches, chaise lounges, ottomans, planters, end tables, bars and bar stools.

For an in-depth look at HDPE Sheets follow this link to: HDPE Sheet – A Complete Guide

These items, when constructed from HDPE plastic sheets, provide numerous benefits to owners over traditional wood or metal items, which are listed below:

• multiple color options;
• design flexibility;
• low maintenance;
• no need to paint them;
• no cracking or breaking is expected; and
• overall longevity of the product.

HDPE Bottles

Recycled milk bottles, composed of just HDPE or, for added toughness, with a copolymer of 2% butane, result in a high-level form of the material for industrial purposes. Bottle-grade HDPE is optimised for blow molding, and is suitable for extrusion into agricultural pipes or household garbage bins. In each product, the recycled HDPE may be blended with new HDPE or a related branched polyethylene to optimise processing and properties, and to ensure uniformity of product.

Film and sheet forms of HDPE are likely to exhibit a decent growth rate of 4.5% between 2016 and 2024. These items are used, respectively, for notebook covers and harsh chemical environments. The material has the advantage of being chemically inert, easily fabricable and affordable. HDPE films are available in a wide variety of styles, depending on their clarity, breakability, flexibility and rigidity.

For an in-depth look at HDPE Bottles follow this link to “HDPE Bottles a Complete Guide“

A note to buyers:

If the material you are buying is due to be applied in weather extremes, it is worth being extra cautious about quality. While HDPE pipelines, for example, are better able to withstand cold-weather installations than heavier, rigid metallic or concrete pipe segments, it is important to specify the expected conditions to your supplier.

Although HDPE has revolutionized low-pressure pipe system design on a global basis, which is testimony to the material’s unique combination of beneficial properties, buyers will want to ensure that their suppliers routinely conduct incident reports and independent forensic failure analysis. Because HDPE pipe-system failure can result in service interruption, safety concerns and loss of brand credibility, it is in your interests that failure analysis reporting is standard practice in your supplier’s operations.

As with any other large-volume business transaction that is time-sensitive and depends heavily on quality and consistency, buying HDPE materials will be more efficient and profitable when trusting relationships have been put in place with your trading partners. Start small when working with a supplier for the first time; don’t over-commit to a long-term deal until you’re confident your supplier can deliver the consistency of volume and quality of material that you require.

HDPE

Quality Control

Product inspection, on the other hand, generally occurs outside of a lab, but rather at the factory where the product is made. It focuses on things like appearance, construction and the basic function of the product. Ideally, your supplier should be able to handle both, and should be audited on a regular basis by accrediting bodies like the Hong Kong Accreditation Service (HOKLAS), ACLASS/ANAB or CNAS.

Next up!

There should be a highly visual production-planning board in place showing, for example, a plan for the week ahead, the company’s supply capability, and how they go about managing big orders.

Do you see simple work instructions up on a wall, or in easy reach, for those manning the assembly line? The instructions should clearly outline the processes for workers at each particular station so there’s never a moment’s doubt during the production.

And, all materials entering the factory should be properly recorded in a systematic inventory, and all machinery adequately maintained. Information related to both should be available for inspection, on request, with maintenance information – including who performed the last inspection and when – clearly labelled on each machine. Then, do you know what to do when a QC inspection fails?

Guidelines with how to proceed include:

• immediately providing detailed instructions to your supplier on what they need to do to rectify the situation;
• insisting on photographs of the new goods while in production and requesting samples once reworked;
• requesting a corrective action report (CAR) that details what the issues were and how they are being corrected in both the short- and long-term; and
• performing a final inspection when the new goods are 20% to 30% complete, which will allow buyers to identify quality issues before the entire order is complete.

Your manufacturer and/or supplier should comply with all the required international certifications and social compliance regulations, specifically those endorsed by the International Standards Organization (ISO) and the Global Social Compliance Programme (GSCP). If you find out they do not, you should take them up on it and move across to a different party until such time as they are up to scratch with their paperwork

HDPE

Recycling

HDPE has a resin identification code (RIC) of “2”. This means it is picked up by most curbside recycling programmes, thereby contributing to the reduction of resource consumption and pollution. Whenever you recycle HDPE plastic, you are helping to create new, reusable eco-friendly products and are preventing millions of pounds of waste from reaching the landfills. More than 80% of all households in the US, for example, have access to a plastic recycling programme that works with HDPE. Recycled HDPE plastic has, in fact, revealed itself to be almost as versatile as its original counterpart due to being utilized in almost as many applications as when in its virgin form. Some of the most common uses of recycled HDPE include:

• Playground equipment;
• Plastic lumber;
• Storage containers;
• Outdoor patio furniture;
• Automobile parts; and
• Compost bins, plastic trash cans and recycling bins.

As a material, HDPE is highly preferred in these and other applications over its heavier counterparts. This enables society and companies employing it to achieve their sustainability goals, which include reducing the amount of material used in packaging products.

Additionally, HDPE’s strong and lightweight nature translates into less impact on the environment. For instance, a recent study of six different types of packaging found that plastic delivers more food with significantly less waste, energy use and global-warming potential than alternatives.

HDPE is lightweight, durable, non-toxic, BPA-free and dishwasher safe; five significant advantages. One of the main reasons why it is so popular is that it is incredibly strong, can be recycled in many different ways and has numerous purposes.

The next time you are looking for safe plastic, make sure you seek out HDPE.