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National Metal and Materials Technology Center
HDPE pipe products from high-quality reworked materials
An industrial prototype demonstrated in this study was developed using plastic scraps generated from the production of high-density polyethylene (HDPE) pipes. The primary objective was to enhance the quality of the reworked compound (RC) to meet the specifications outlined in the Thai Industrial Standard (no. 982-2556). The development process involved five key steps: (a) Characterization of the reworked compound and the virgin compound to identify any inferior properties. (b) Selection of plastic additives to enhance the deficient properties of the reworked compound, taking into consideration economic factors. (c) Investigation and formulation of the reworked compound and selected additives using Design of Experiment (DOE) principles. (d) Field-testing of the manufacturing of HDPE pipes using the developed high-quality reworked compound (HQ-RC). (e) Establishment of a process for producing a masterbatch containing the selected plastic additives.
An enhancement of the reworked compound’s quality requires the utilization of two distinct groups of additives. The first group is designed to regulate the oxidation induction time (OIT) and includes antioxidants (both primary and secondary) and a light stabilizer. The second group is employed to manage the melt flow rate (MFR) through the use of a dicumyl peroxide (DCP) crosslinker. The resultant high-quality reworked compound (HQ-RC) demonstrates a substantial increase in the OIT value, surpassing 30%, while simultaneously reducing the MFR. Furthermore, the occurrence of die drooling, which typically leads to high-surface roughness and defects on the pipe surface, is significantly diminished when using the developed high-quality reworked compound. The surface quality of pipes produced from this advanced reworked compound closely resembles and is comparable to that of pipes produced from virgin compound.
WIIK PUBLIC Co., Ltd. has successfully manufactured HDPE pipes using the developed high-quality reworked compound (HQ-RC). These pipes, with diameters ranging from 110 mm to 1600 mm, have undergone rigorous testing in accordance with Thai Industrial Standard no. 982-2556. They have not only met the required standards but have also demonstrated properties similar to those of pipes made from virgin compound. Furthermore, the pipes manufactured from the HQ-RC have received recognition for their innovation in Thailand. They were awarded the Thai innovation numbers 02010031, WIIK ECONOMY QUALITY PIPE (W-EQ PIPE) in August 2022 and 01010067, WIIK ECONOMY POTABLE PIPE (W-EP PIPE) in January 2023. These pipes, produced using the HQ-RC, are now commercially available.
Research team
Dr.Wuttipong Rungseesantivanon, Dr.Bongkot Hararak, Dr.Bunpot Mai-ngam, Dr.Charinee Winotapun, Dr.Rittirong Pruthtikul, Kawin Keeratipinit, Sanya Kaewket, Dumrong Thanomjitr, Natcha Prakymoramas and Pakjira Sirirutbunkajal
