Choosing the right plastic for your application can be confusing, particularly if you are new to the industry. In our recent blog post, “When it Comes to Material Selection, Not All Plastics Are Created Equal," we gave a quick overview of the polymers that Impact extrudes, touching on their general characteristics and typical uses.
In this next blog post, we narrow our focus to discuss one of the plastic sheet materials produced by Impact in greater detail – High Density Polyethylene (HDPE). HDPE is one of the most versatile plastics and is the most widely used polymer for consumer products. Below are 7 important facts about HDPE plastic:
- HDPE has a higher density than other grades of PE:
High Density Polyethylene is exactly what it sounds like – it is a grade of polyethylene that carries with it a higher density in comparison to other available grades of PE. Polyethylene is created from the polymerization of ethylene, which produces very long, straight chains of hydrocarbon monomers. By adjusting the polymerization process, these chains can be made to branch, and the degree of branching determines the grade of PE that is produced. With HDPE, there is minimal branching of the polymer chain, which means that the molecules are packed tightly together during crystallization leading to increased density and rigidity.
- HDPE is a semi-crystalline polymer:
An important distinction between different thermoplastic polymers is amorphous vs. semi-crystalline. HDPE is a semi-crystalline polymer which means that the plastic exhibits organized and tightly packed molecular chains. The areas of crystallinity are called spherulites and can vary in shape and size with amorphous areas existing between the crystalline areas. The degree of crystallinity affects many characteristics of the polymer. In the case of HDPE, this results in greater density and greater strength.
- HDPE is lightweight and strong:
As noted above, the high crystallinity of HDPE results in a stronger product with a higher density. Despite the increased density compared to it’s PE counterparts, HDPE still maintains a lower density than many other polymers, with only polypropylene and grades of Low Density PE coming in lower on the charts. However, despite this low density and light weight, HDPE is very strong and has excellent impact strength. Because of the excellent strength to weight ratio, HDPE is a suitable material for inter-material replacement of heavier materials, resulting in less solid waste by weight and a more sustainable solution.
- HDPE is versatile:
HDPE is one of the most versatile plastics and has may different uses spanning across various industries – from food packaging, to medical packaging, to construction. The typical consumer most likely handles an HDPE bottle or container on an almost-daily basis. This material also comes in many forms, such as Tyvek, which, when paired with rigid HDPE, creates a single recycling stream for the package. In addition, Impact Plastics also carries USP Class VI certified HDPE resins for medical device applications.
- HDPE is recyclable:
Speaking of recycling, HDPE is an easily recyclable material, with nearly all curbside programs in the US accepting HDPE. In fact, Moore’s ‘2015-16 Centralized Study on Availability of Recycling’ report found that over 60% or greater of the US population has access to recycling programs that accept HDPE rigid packaging. In addition, Moore’s 2014 Non-bottle Rigid Plastic Recycling study reported HDPE rigid containers to have the second highest recovery rates at 34.1%, second only to polypropylene at 38.3%.
Not only are recovery rates high for this material, but there are many opportunities for diversion into other applications. Recycled HDPE is currently being used in applications such as plastic storage containers, plastic lumber, patio furniture, automobile parts and recycling bins. Considering all of these factors, you can be sure that with HDPE you are making a sustainable material choice.
- HDPE is an effective moisture barrier:
This material is particularly useful for applications where moisture resistance is a critical specification. HDPE has a Moisture Vapor Transmission Rate (MVTR) of 0.5 (g-mil.100 in. 2/24hr.). MVTR is a measure of the passage of gaseous H2O through a barrier – the lower the rate, the longer the package protects its contents from moisture and ensures that moisture of the product remains the same. Polypropylene has the same MVTR as HDPE. As a basis of comparison, Polystyrene has an MVTR of 10.0, PET has an MVTR of 2.0, and PVC an MVTR of 3.0. So for applications requiring a good moisture barrier, HDPE or polypropylene will yield the best results.
- HDPE has good chemical resistance:
In addition to being an effective moisture barrier HDPE is also an excellent resin of choice for applications that require good chemical resistance. This material provides a good resistance to organic solvents, degreasing agents and electrolytic attack. This material also has good Environmental Stress Crack Resistance (ESCR). Brittle stress cracks or fractures, called environmental stress crack, occurs in some plastics when exposed to surface active wetting agents such as alcohols, soaps, surfactants, or others. The ability of a polymer to resist the environmental stress cracking is called ESCR. Depending on the grade of polyethylene used, this can range from several months for a milk or juice bottle to several decades for an automotive tank or pipe.
Download our HDPE data sheets to learn more about HDPE from Impact Plastics!
Interested in learning more about HDPE and the other polymers offered by Impact Plastics? Get in touch with our team!