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Sustainability / Natural Solutions
Manufacturing companies that produce plastic parts and components often use Post-Consumer Resin (PCR) or Post-Industrial Resin (PIR) to create strong, durable, and lightweight products. However, a few common problems can arise when using these materials: warping, shrinking, and delamination. In this article, let’s take a look at each of these issues and provide some tips and suggestions to avoid them.
Post-Consumer Resin (PCR) – An Overview
The term Post-Consumer Resin is used for the plastic products that are typically used for recycling, i.e., water bottles, tubs, baskets, jugs, toys, etc. These cannot be perfectly segregated, so no PCR stream is homogenous as it has uncontrolled heat history. PCR tends to have non-polymer contaminants. It is often made from mixed waste streams and may not be as consistent in quality or performance as its virgin counterpart.
Post-Industrial Resin – An Overview
The term
‘Post-Industrial Resin’ is specifically used for the material that the consumer does not use. As the consumer does not touch it, it is more homogenous and has a relatively controlled heat history. For example, excessive material being removed in the form of chips in an industry will go under the recycling process.
Problems Associated with PCR and PIR
The usage of Post-Consumer Resin (PCR) and Post-Industrial Resin (PIR) in plastics is becoming increasingly popular. There are many tax incentives in the EU to maximize the level of recycle plastic into the original application. The most critical and technically difficult area is to increase the level of PCR and PIR in LLDPE films without sacrificing the performance of the films.
Some of the issues that can arise when using post-consumer resin (PCR) or post-industrial resin (PIR) in plastic products are: PCR and PIR can contain impurities affecting the finished product, disruptive supply, and heat history. For example, suppose the resin is not adequately cleaned. In that case, it can contain contaminants like dirt, dust, or metals that can cause problems with the finished product resulting in the “
downcycling” of products.
Upcycling is the process of turning post-industrial resin into a higher quality product. This means that the plastic can be recycled and made into a new product that is better than the original material. For example, the post-industrial resin can be upcycled into new plastic products that are stronger and more durable than the original material.
Upcycling is desired by plastic product formulators while using PCR and PIR. Moreover, amid increased demand for the PCR, the supply is disturbed leading to higher prices. Higher prices are undesirable and lead to unprofitability. Also, EU countries impose taxes on producers who do not have 30% PCR in their plastic.
Another challenge associated with the use of PCR and PIR is “gels.” Wood fibers, paper fibers, and water bubbles are considered gels. Heavy cross-linked chunks of polymer form spots on the film which is undesirable in plastic products. Gels also lead to the breakage of the film.
Moreover, the heat history of the plastic product is unknown since PCR/PIR are added to the material. In PCR, different materials are mixed up which contain plastics with different heating temperatures. When two plastics with different melting points are heated together, the forming material contains overheated materials with longer heat history.
Before we move on, let us understand some common terms associated with these resins.
Heat History:
The term
“heat history” refers to the number of times plastic is heated while processing. The more the material is recycled, the more heat histories it will have. For a conventional plastic film, a typical processing procedure would include:
- Creation of fluff resin
- Extrusion of pellets
- Film processing
Gels:
Gels are large polymer molecules in which bonding between molecules has occurred, usually through other means such as oxidation. The formation of the gel reduces the surface finish and overall quality. It also reduces the strength of the final product.
Let us look at a possible solution available in the industry that can help improve the overall quality of the recyclate.
Dover Chemical Corporation offers
Doverphos LGP-12 liquid phosphite, a new type of plastic additive that can improve the recycling of plastics. It can make recycled plastic products more durable with a longer life span.
In addition, LGP-12 can also
help to reduce the environmental impact of plastic production. LGP-12 increases the lifespan of plastic material and allows control of the recycling of plastic products. The use of LGP-12 increases the lifespan and quality which reduce the need to recycle plastic. The carbon footprint is directly related to recycling. As recycling increases, carbon foot will be increased which challenges sustainability and the environment.
Many additives exhibit migration, which is the undesired effect of moving towards the surface of the polymer, creating plate-out and bloom issues. Plate-out is when molecules accumulate on the surface of a material, causing it to become dull and discolored. Bloom is when molecules migrate to a material's surface and then evaporate, leaving behind a powdery residue. The rate of migration is often directly proportional to molecule size. Because Doverphos LGP-12 is polymeric, it is a large molecule, and migration reduces greatly, allowing for higher loading levels for increased performance. To test this, an experiment was performed with three specimens including 100% LLDPE PCR, 250 ppm LGP-12, and 500 ppm LGP-12. The observations recorded are represented by the graph below.
For further reading: Why Doverphos LGP-12 is the natural choice for phosphites?
MFR (190°C @ 216 Kg) under 245°C Melt Temp
The graph shows the effect of using LGP-12 with LLDPE PCR. The pass on the horizontal axis represents each heat history and aims to keep the bar as flat as possible. The grey bar represents the mixture of 500 ppm LGP-12 into LLDPE PCR (weighted 2.16 kg) manufactured at a temperature of 190 degree Celsius. In the above figure, each pass represents another heat history. It was found that the addition of 250 ppm LGP-12 and 500 ppm LGP-12 into the PCR upcycled the process. To deal with the polymer stability, LGP-12 possesses great properties and is formulated to be consumed in the process. Additionally, Doverphos LGP-12 is an effective phosphite stabilizer that can help lower the color of recycled plastics. It is highly efficient in reducing the yellowness of recycled plastics, making them more attractive and marketable.
OTT Data under 245°C Melt Temp
The above graph shows the data from the experiment conducted to compare 100% LLDPE PCR, 250 ppm LGP-12, and 500 ppm LGP-12. These three compositions of the plastic materials are represented with blue, orange, and grey lines in the graph, respectively. The OIT data were collected for the compound pass and the 4th pass to compare the residual LGP-12 in the polymer. The higher the number, the better stabilized the polymer is. It is concluded from the results that the grey bar showed maximum residual of the polymer after the pass 4. Although phosphites are formulated to be consumed in the process, it is concluded that Doverphos LGP-12 has upcycled the process. While there is still LGP-12 left, it can be further processed as PIR, if necessary.
Also check out this webinar: Novel Phosphite Stabilizers for Changing Global Market
The LGP-12 is effective in preventing the production of gels, both in terms of number and size, in industrial testing. Multiple trials virtually removed big gels, allowing the film with 30% PCR to be physically evaluated beside virgin material for comparison. Due to gels, a PCR or PIR-containing film is currently downcycled to a lower grade.
Conclusions
In a time when the world is increasingly looking for ways to reduce downcycling and increase upcycling, Doverphos LGP-12 offers a cost-effective way for plastic film manufacturers to do just that. By reducing the amount of waste produced in their manufacturing process, filmmakers can save money while also doing their part in preserving the environment. Have you tried using Doverphos LGP-12 in your production process? Let us know how it went!
In light of the above-conducted trails, it is concluded that only a small portion of Doverphos LGP-12 can add a huge difference to the PCR and PIR by increasing the stability and performance of the material resulting in desirable yet cost-efficient films. The ordering procedure is made simple for your convenience. Please send us your requirements and our team will reach out to you.
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