Grantee Research Project Results
2021 Progress Report: Nanoclay Reinforced Recycled HDPE to Replace PVC and PE Water Pipe Materials
EPA Grant Number: SU840159Title: Nanoclay Reinforced Recycled HDPE to Replace PVC and PE Water Pipe Materials
Investigators: Na, Sukjoon , Youn, Sungmin
Institution: Marshall University
EPA Project Officer: Page, Angela
Phase: I
Project Period: December 1, 2020 through November 30, 2021 (Extended to November 30, 2022)
Project Period Covered by this Report: December 1, 2020 through November 30,2021
Project Amount: $24,946
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2020) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Chemical Safety
Objective:
High density polyethylene (HDPE) is one of the most widely used plastics in household products and engineering applications due to its good mechanical properties, chemical and corrosion resistance, low cost, and ease of processing. However, with the increased use of HDPE, the concerns about the accumulated plastic waste have grown due to its permanence in the environment. Although the utilization of recycled HDPE can offer many benefits towards plastic waste management, recycled HDPE materials are prone to possessing inferior properties compared to pristine counterparts. Thus, recycled plastics are not recommended for engineering applications, particularly in critical infrastructures.
To improve the sustainability of HDPE and suggest a solution to those arisen concerns, this EPA P3 Phase I project aims to evaluate the applicability of nanoclay reinforced recycled high density polyethylene (HDPE) as a potential water pipe material that can be applied in aggressive chemical environments. Polymer nanoclay composites have continuously received great attention as an alternative to a new class of pipe materials due to their potentially enhanced material properties. Several remarkable improvements in properties of nanoclay composites have been reported. For example, incorporating a small amount of nanoclay into thermoplastic polymers significantly increases tensile strength and modulus. In addition, impermeable and dispersed nanoclay in a polymer matrix increases the length of the diffusing gas path, leading to an increase in barrier properties.
Based on those reported improvements, we assume that nanoclay may also enhance the resistance to chemical degradation and failure under severe chemical conditions. Our current hypotheses for the project are that (1) incorporating nanoclay into recycled HDPE will enhance the chemical resistance of composites, and thus allow the use of recycled HDPE for water pipe systems; (2) chemical resistance of degradation behavior will vary with the compositions of nanoclay and recycled HDPE contents; (3) ultimately, nanoclay reinforced recycled HDPE will be a new group of sustainable materials that utilized recycled plastics and environmental-friendly nanoclay.
Progress Summary:
The team’s work during the first six months of the project period focused on blending materials and extruding filaments for the use of a commercially available 3D printer. Two types of pristine HDPE resins with high Melt Flow Rate (MFR) of 8.50 g/10 min and low MFR of 0.300 g/10 min, respectively, were kindly donated by Braskem America while the recycled HDPE pellet collected from the number “2” stamped products such as milk jugs and water bottles was provided by Envision Plastics. The organo-modified montmorillonite containing dimethyl dialkyl (C14-C18) amine as a surface modifier was supplied by Sigma-Aldrich in the form of powder. The pristine, recycled HDPE pellets and nanoclay used in this study are shown in Figure 1.
Figure 1: (a) Pristine HDPE pellets, (b) recycled HDPE pellets, and (c) nanoclay powder
The pristine and recycled HDPE filaments for the use of a 3D printer were produced utilizing a 3Devo Composer 350 single-screw extruder equipped with four independently controlled heating zones. The lab-scale extruder and filaments with various pristine, recycled, and nanoclay compositions are shown in Figure 2.
Figure 2: (a) Lab-scale polymer extruder, and (b) extruded test filaments
For the fabrication of good quality filaments, the team has conducted parametric studies to find the optimal range of extrusion temperature and rate. The fabricated filaments in Figure 2 were extruded at temperatures between 190 and 210 at a different rate of extruding speed.
Morphological characterization
For evaluation of the surface morphology and quality of extruded filaments, scanning electron microscopy (SEM) was conducted. A constant shape and diameter of filaments is the prerequisite for the fabrication of test specimens using a commercially available 3D printer that uses a filament with a diameter of 1.75 mm. Our preliminary tests showed that the extruded filaments were oval (Fig. 3a and c), and the dimensions were inconsistent. Several factors such as extrusion temperature and speed may affect the quality of HDPE filaments. Our team is currently conducting a parametric study to achieve uniform filaments. Figure 3d displays the distribution of nanoclay particles in a polymer matrix.
Figure 3: SEM images of the cross-sectional area of the filaments
Educational aspects and teaching the P3 approach.
Providing a research experience and building student knowledge in the P3 approach was one of the main goals of our P3 project. The PI and Co-PI surveyed student researchers who participated in the P3 research activities for the past six months to evaluate the educational impact of the current project. They are the students who are the first in line for exposure to the educational benefits of the P3 project. Four out of five student researchers (four undergraduate students and one graduate student) answered the survey. Table 1 showed survey questions and responses (on a 1-5 scale from strongly disagree to strongly agree).
Generally, the current project has very positive educational impacts of the P3 approach on the student researchers. The PI and Co-PI plan on making a lecture about the P3 approach based on the current P3 project results and delivering in the PI and Co-PI’s engineering courses to expand the educational impacts of the P3 project to more students at Marshall University.
Future Activities:
Our team encountered challenges in the process of manufacturing HDPE filaments and printing test specimens using a 3D printer. Determining the proper parameters such as temperatures, extrusion rate, and printer bed materials is essential for the quality of test materials and specimens. We expect that our ongoing parametric studies will allow us to optimize those parameters for the fabrication of materials and focus on the remaining research tasks for the next six months.
Journal Articles:
No journal articles submitted with this report: View all 3 publications for this projectSupplemental Keywords:
water pipe, HDPE, recycled plastics, nanoclay, polymer nanoclay composites, fracture toughness, chemical resistance, sustainable material, degradationRelevant Websites:
EPA P3: Nanoclay reinforced recycled HDPE to replace PVC and PE water pipe materials. (YouTube Video) Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.