Effect of Recycled High-Density Polyethylene on the Impact Strength of Polybutylene Terephthalate/Polyamide 6

Abstract

Recycling high-density polyethylene (HDPE) is crucial to addressing plastic waste challenges. This study investigates the mechanical properties of blends composed of HDPE, polybutylene terephthalate (PBT), and polyamide 6 (PA6). Blends with varying HDPE content (0, 70, 80, 90, and 100%) were analyzed using injection molding to determine their impact toughness and structural characteristics. PBT and PA6 (blended in a 50:50 ratio) were combined with HDPE to create composites with enhanced properties. Testing included unnotched impact strength analysis and scanning electron microscopy (SEM). HDPE, a flexible thermoplastic, was paired with PBT and PA6, known for their strength and heat resistance, to produce a blend with superior mechanical performance. Results reveal that incorporating HDPE enhances the impact toughness of the composites compared to the pure PBT/PA6 blend, offering promising potential for many diverse applications in materials engineering in the automotive industry, household products, and protective casings of electronic products.

Keywords

HDPE / PBT/PA6 blends / Impact strength / Microstructure

Acknowledgments

We acknowledge HCMC University of Technology and Education, Dong Nhan Phat Co., Ltd., and Material Testing Laboratory (HCMUTE). They allowed us to join their team and access the laboratory and research machines. With their appreciated support, it is possible to conduct this research.

Author Contributions

Conceptualization, P.T.H.N.; Methodology, T.H.N.; Software, B.H.D.; Validation, D.Q.T.; Formal Analysis, T.H.N., B.H.D. and D.Q.T.; Investigation, D.T.V.A.; Resources, N.C.T. and P.Q.A.; Data Curation, N.V.T.; Writing—Original Draft Preparation, T.H.N., B.H.D. and D.Q.T.; Writing—Review & Editing, P.T.H.N.; Visualization, P.T.H.N.; Supervision, P.T.H.N.; Project Administration, P.T.H.N. During the preparation of this work, the authors used Grammarly to improve readability and language. After using this tool/service, the authors reviewed and edited the content as needed and took full responsibility for the publication's content.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data used to support the findings of this study are available from the corresponding author upon request.

Funding

This work belongs to the project in 2025 funded by Ho Chi Minh City University of Technology and Education, Vietnam.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

[1] Zimmermann L, Dierkes G, Ternes TA, Völker C, Wagner M. Benchmarking the in vitro toxicity and chemical composition of plastic consumer products. Environ. Sci. Technol. 2019, 53, 11467-11477.

[2] Vogt B, Stokes KK, Kumar SK. Why is Recycling of Postconsumer Plastics so Challenging? ACS Appl. Polym. Mater. 2021, 3, 4325-4346.

[3] Islam MZ. Prevention policies for the marine ecological environment in the South China Sea as a consequence of excessive plastic compound use in Vietnam. Integr. Environ. Assess. Manag. 2024, 20, 2088-2106. doi:10.1002/ieam.4971.

[4] d’Ambrières W. Plastics recycling worldwide: Current overview and desirable changes. Field Actions Sci. Rep. 2019, 19, 12-21.

[5] Chen S, Hu Y. Advancements and future directions in waste plastics recycling: From mechanical methods to innovative chemical processes. Chem. Eng. J. 2024, 493, 152727.

[6] HamaSalih HA, Abdalrahman RM, Rostam S. Optimizing the blending ratio and processing parameters for ternary blends of recycled polypropylene with recycled high and virgin linear low-density polyethylene. Results Eng. 2023, 18, 101171.

[7] Dittrich G, Straka Ľ, Botko F, Duplák J, Bircak J, Aldaihan F. Influence of recycled PA6 and PBT plastic material on the bonding strength. MM Sci. J. 2019, 10, 3005-3010.

[8] Tesfaw S, Fatoba O, Mulatie T. Evaluation of tensile and flexural strength properties of virgin and recycled high-density polyethylene (HDPE) for pipe fitting application. Mater. Today Proc. 2022, 62, 3103-3113.

[9] Akdoğan E. The effects of high-density polyethylene addition to low-density polyethylene polymer on mechanical, impact and physical properties. Eur. J. Tech. 2020, 10, 25-37. doi:10.36222/ejt.646693.

[10] Yang H, Yilmaz G, Jiang J, Langstraat T, Chu R, van Es M, et al. Thermal, rheological, and mechanical characterization of compression and injection molded ultra-high molecular weight polyethylene, high-density polyethylene, and their blends. J. Appl. Polym. Sci. 2023, 140, e53484.

[11] Yin B, Li LP, Zhou Y, Gong L, Yang MB, Xie BH. Largely improved impact toughness of PA6/EPDM-g-MA/HDPE ternary blends: The role of core-shell particles formed in melt processing on preventing micro-crack propagation. Polymer 2013, 54, 1938-1947.

[12] Vidakis N, Petousis M, Maniadi A. Sustainable Additive Manufacturing: Mechanical response of high-density polyethylene over multiple recycling processes. Recycling 2021, 6, 4. doi:10.3390/recycling6010004.

[13] Wang GX, Li S, Feng Y, Hu YX, Zhao GY, Jiang W. Effectively toughening polypropylene with in situ formation of core-shell starch-based particles. Carbohydr. Polym. 2020, 249, 116795.

[14] Guo JJ, Wu Y, Lu XY, Nie M. Toughening mechanism of α/β core-shell structure for high toughness polypropylene random copolymer. Polymer 2024, 298, 126931.

[15] Zhu L, Wang HM, Liu MH, Jin Z, Zhao K. Effect of core-shell morphology on the mechanical properties and crystallization behavior of HDPE/HDPE-g-MA/PA 6 ternary blends. Polymers 2018, 10, 1040.

[16] Qiu BW, Chen F, Shangguan YG, Zhang L, Lin Y, Zheng Q. Simultaneously enhancing strength and toughness for impact polypropylene copolymers by regulating the dispersed phase with high-density polyethylene. RSC Adv. 2014, 4, 58999-59008.

[17] Wang BL, Wu D, Zhu L, Jin Z, Zhao K. High-density polyethylene-based ternary blends toughened by PA6/PBT core-shell particles. Plast. Tech. Eng. 2017, 56, 1908-1915. doi:10.1080/03602559.2017.1295314.

[18] Lin JH, Pan YJ, Liu CF, Huang CL, Hsieh CT, Chen C, et al. Preparation and compatibility evaluation of polypropylene/high-density polyethylene polyblends. Materials 2015, 8, 8850-8859. doi:10.3390/ma8125496.

[19] Pham N, Nguyen VT. Morphological and mechanical properties of Poly (Butylene Terephthalate)/High-Density Polyethylene blends. Adv. Mater. Sci. Eng. 2020, 2020, 8890551.

[20] Sapsrithong P, Sritapunya T, Tuampoemsab S, Rattanapan A, Nithitanakul M. Morphology and mechanical properties of Polyamide 6 and Polybutylene Terephthalate blends compatibilized with Epoxidized Natural Rubber. IOP Conf. Ser. Mater. Sci. Eng. 2020, 811, 012019.

[21] Tantry S, Anantharaman D, Thimmappa BHS, Kamalakaran R. Studying banded spherulites in HDPE by electron microscopy. Polym. Test. 2020, 89, 106631.