Off Grade HDPE Pellets are an excellent homogeneous source of off grade HDPE. For those not familiar with Off Grade HDPE, it is simply a term used to describe HDPE that does not fall within one standard grade or another. Falling under the umbrella of HDPE are many differing grades of HDPE, suitable for different purposes. Injection molding grade HDPE, for example, has a very low viscosity and flows quickly. This makes it ideal for injection molding applications where the HDPE must flow quickly into the die. Then there is pipe grade HDPE. Pipe grade HDPE is stronger and much more dense than injection molding grade HDPE, as it needs to be able to withstand greater physical forces, and it also needs to be fairly resistant to chemicals.
Off Grade HDPE is normally produced when a production plant is switching from making one grade of HDPE to another. If a plant is making injection grade HDPE, and must switch to pipe grade HDPE, there is likely to be at least one batch which does not meet the specifications for any grade. The HDPE produced in these batches is known as Off Grade HDPE.
Off Grade HDPE is still of a high quality, and structurally sound, though it may not suit the rigors of high stress applications. Manufacturers who are producing products that do not need to perform under extreme conditions may find that Off Grade HDPE may be an excellent way of lowering their material costs, whilst still producing a quality product.
Off Grade HDPE pellets are made in exactly the same way as other forms of HDPE Pellet. If the Off Grade HDPE pellets are being made from virgin HDPE (virgin HDPE being the term for freshly manufactured HDPE), then the freshly polymerized HDPE, which is a liquid, is extruded through a die, cut into pellets by a sharp blade, and then cooled.
Reprocessed Off Grade HDPE Pellets
It is also possible to obtain reprocessed off grade HDPE pellets. Reprocessed off grade HDPE pellets are pellets formed from scrap HDPE which is also off grade. At this point, it is worth noting that the term “off grade” does not denote lower quality. When purchasing reprocessed HDPE, care should be taken to ensure that contamination levels fall within an acceptable range for your application. Scrap HDPE is generally exposed to a wide range of contaminants during its life time, including dirt, metals, rocks, labels, and other plastics. During reprocessing every effort is made to ensure that these contaminants are washed away, and then later on filtered out of the HDPE, however no contamination removal process is 100%, which is why reprocessed HDPE is not approved for food contact applications.
Reprocessed HDPE may also be weakened structurally due to undergoing several heat cycles. It is possible to heat and reheat HDPE many times over, however, with each heating it becomes more likely that the molecular structure of the HDPE will begin to break down, as the molecular bonds within the HDPE weaken. This weakening is generally not significant for most applications, however, and reprocessed HDPE is used with confidence by thousands of manufacturers world wide.
Another factor to take into consideration is that reprocessed off grade HDPE pellets are also likely to be colored, due to label dyes and colored HDPE that was included in the scrap HDPE stream during processing. For this reason, reprocessed off grade HDPE is generally better for applications where appearance is not of huge importance. To save costs, some manufacturers use reprocessed off grade HDPE for inner layers of a product, and then put a layer of virgin reprocessed HDPE on the outside. This creates a product that is low cost to produce, but is still visually appealing to the consumer.
Why Off Grade HDPE Pellets?
If you choose reprocessed off grade HDPE, you may have the choice of using off grade HDPE pellets, or using even lower cost shredded HDPE scrap. For most manufacturing applications, off grade HDPE pellets are recommended because by being in pellet form, the HDPE forms a homogeneous HDPE supply to your production line when it is melted down. HDPE pellets are formed from shredded HDPE scrap that is melted down, mixed thoroughly, and then filtered to remove as much contamination as possible. This means that when you melt down HDPE pellets, you are left with liquid HDPE that has a consistent quality throughout the mass.
Shredded HDPE is not filtered in the same way that HDPE pellets are, and when shredded HDPE is melted, the manufacturer is left with a product which contains some high quality areas, and other low quality areas within the liquid mass. This then passes through the production line, creating some products that meet standards, and others which do not. The manufacturer must then spend time identifying and removing the defective products, and is also risking defective products being missed and sent out to consumers, something that can result in costly recalls. Generally speaking, off grade HDPE pellets are the best sources of off grade HDPE when all costs are taken into account.
Off Grade HDPE Pellets prices and suppliers
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