Variability and quality control for production of corrugated HDPE pipe manufactured with recycled content
Crista K. McNish, Joe Babcanec, Rachel M. Thurston, Zacharias Obermeyer
Papers # 2018 Las-Vegas
This paper presents findings from extensive testing performed on various recycled HDPE resins at different stages of processing to evaluate: (1) the variability expected from a source resin (e.g. post-consumer materials from bulk recycling, post-industrial waste stream), (2) variability when blending different types of HDPE (e.g. high molecular weight resin, wide spec resin), (3) variability through processing (e.g. pelletizing), and (4) variability within the final pipe product. By quantifying the variability of each phase in the handling and manufacturing process, manufacturers can implement best practices and inspectors/specifiers can set minimum test frequencies to ensure consistent, quality pipe is produced to meet performance requirements specified in ASTM and AASHTO recycled HDPE pipe product standards.
The worldwide usage of high density polyethylene (HDPE) is estimated at 47,980 thousand metric tons this year with usage expected to continue to rise over the next several years (1). North America continues to have a significant share of HDPE volume with usage coming in various product forms, most commonly as consumer packaging and containers with relatively short-term use. With the number of short-term use products being disposed of by both consumers and industry, there is significant potential to recycle the HDPE material and repurpose the material for use as other products. One such use is production of gravity-flow drainage pipe. When repurposed for use as drainage pipe, the HDPE material that may otherwise have been disposed of in a landfill after short-term use, is used for applications that are generally designed with an installed service life of 50 and more years (2).
A primary focus of ensuring high performance of recycled-content HDPE drainage pipe is development of test methods and minimum test requirements that accurately quantify the quality of the resin being used for pipe production. This initiative has been underway in both ASTM and AASHTO associations through many years of research leading up to today, where performance-based product standards are being evaluated and implemented that allow the use of recycled-content pipe products. The next logical step in the implementation of product specifications is the development of quality control measures that ensure an inherently variable stream of HDPE source materials and blends are tested at a frequency that adequately characterizes the performance of the material as a finished pipe product.
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