| August 30, 2023
Today, we'll delve into the world of regrind and its impact on plastic part production. Regrind offers a solution to minimize plastic waste. However, it's crucial to understand the technical considerations and challenges that come with using regrind effectively.
Challenges with Regrind
Using regrind can lead to various issues like contamination, inconsistent pellet configuration, glass fiber breakage, and polymer degradation. These problems can wreak havoc on dimensional control, processing consistency, and the overall quality of the final plastic part.
Contamination is often the result of improper material handling. To avoid this, it's essential to establish specific and detailed material handling procedures. Properly cleaning grinders and hoppers and keeping material containers covered are just a few of the essential steps that need to be taken to maintain the purity of the regrind.
Glass-filled materials commonly exhibit some degree of fiber breakage during processing and regrinding. Using such reground material can lead to reduced mechanical properties, particularly tensile and impact strength. Moreover, maintaining dimensional control becomes more challenging due to changes in shrinkage rates. The extent of these issues depends on the amount of fiber breakage and the quantity of regrind utilized.
One common misconception about regrind is that it might process better than virgin material. While this may be true in certain cases, such as when dealing with hygroscopic resins with hydrolytic degradation or thermally degraded materials, it's important to note that the mechanical properties of the regrind are compromised. As a result, the final parts molded from regrind will have diminished mechanical attributes, which can impact their performance in applications.
Consideration for Regrind Particle Size
Another crucial factor to consider is the particle size of the regrind. The size of the particles, whether big chunks, small chunks, or fines, can significantly affect the performance of the regrind. Inconsistent sizes, especially large variations, may lead to non-uniform melting and variable drying rates for hygroscopic resins. This can cause issues such as variations in shrinkage, part weights, dimensional results, warpage, functional deficiencies, and even non-melt in the parts, particularly for semi-crystalline materials. Additionally, fines can cause unwanted black specs or discoloration streaks in transparent or translucent materials.
Methods of Regrind Use
There are several schools of thought on how to handle regrind in plastic part production:
Regrind undoubtedly has a significant role to play in reducing waste in the plastics industry. However, its successful implementation relies on establishing proper procedures and disciplines on the production floor. Regardless of the chosen method, it is crucial to ensure that parts produced with regrind are fully qualified to minimize any potential performance risks.
We hope you found this Tech Tip informative and useful for your plastic part production processes. Stay tuned for more insights into the world of plastics in our future blog posts!
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Kelly Bailey | Senior Application Development Engineer
Kelly is a Senior Application Development Engineer, with over 25 years of industry experience. He has supported our Corporate Account customers during his 10 years with Nexeo Plastics, providing technical expertise in DFMA, Part Design, Mold Design, Moldflow Simulations, Processing, Secondary Processes, Validation & Testing, Failure Analysis, and Material Selection. He supports customers in all markets, including healthcare, automotive, consumer, industrial, lawn and garden, agriculture, and E&E to name a few. Kelly has a Bachelor of Science in Plastics Engineering Technology from Penn State.
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