Mechanic of Advanced and Smart Materials
Quarterly

Characterization of the Shape Memory Effect of Recycled HDPE Filament

Document Type : Original Article

Authors

Sina Farahifar
Mahmood Mehrdad Shokrieh

School of Mechanical Engineering, Iran University of Science and Technology, Tehran,, Iran

https://doi.org/10.66224/masm.5.3.421
Abstract
Developing low-cost recycled filaments with desirable mechanical properties is a major challenge in the additive manufacturing industry. This research investigated the feasibility of producing 3D-printer filament from recycled high-density polyethylene (HDPE) bottle caps and characterized its shape-memory behavior. Unlike previous studies that neglected the residual stress history from production and spooling, this study demonstrated the inherent error in conventional testing methods by measuring the initial curvature angle and its variation after stress relaxation. The fabricated 1.75 mm filament was subjected to shape-memory bending tests, and the results were compared with those of commercial PLA, ABS, and TPU filaments. The recycled filament, with a shape-recovery ratio of about 80%, behaved similarly to PLA and outperformed ABS. Furthermore, the necessity of a stress-relaxation step in testing protocols was confirmed by observing a non-zero initial angle and unwanted shape recovery after stress relaxation in all samples. The fabricated filament also exhibited a lower density than the other materials, providing a key competitive advantage. Additionally, economic analysis revealed a significant cost reduction compared to commercial counterparts. It is concluded that high-value smart materials do not require expensive resources; recycling bottle caps is presented as an environmentally friendly solution with high application potential, affordability, and significant added value.

Keywords

Recycled shape memory filament
Shape memory polymers
Shape memory properties
3D printer
High-density polyethylene (HDPE)
[1] Fang C, Wang W. Shape memory alloys for seismic resilience. 1 ed: Springer Nature Singapore, 2019.
[2] Vernon LB, Vernon HM. Process of manufacturing articles of thermoplastic synthetic resins. 1941- 993.
[3] Das HR, Uthaman A, Lal HM, Babu A, Thomas S. Shape memory polymers as sutures. In: Thomas S, Coates P, Whiteside B, Joseph B, Nair K, editors. Advanced Technologies and Polymer Materials for Surgical Sutures: Woodhead Publishing; 2023. 265-81.
[4] Hu J. Shape memory polymers: fundamentals, advances and applications. Shrewsbury, UK: Smithers Rapra, 2014.
[5] Abavisani I, Rezaifar O, Kheyroddin A. Multifunctional properties of shape memory materials in civil engineering applications: a state-of-the-art review. Journal of Building Engineering. 2021;44:102657.
[6] Peponi L, Navarro-Baena I, Kenny JM. Shape memory polymers: properties, synthesis and applications. In: Aguilar MR, San Román J, editors. Smart polymers and their applications: Woodhead Publishing; 2014. p. 204-36.
[7] Xie T. Tunable polymer multi-shape memory effect. Nature. 2010;464:267-70.
[8] Chen Y, Chen C, Rehman HU, Zheng X, Li H, Liu H, et al. Shape-memory polymeric artificial muscles: mechanisms, applications and challenges. Molecules. 2020;25:4246.
[9] Hu J, Zhu Y, Huang H, Lu J. Recent advances in shape-memory polymers: Structure, mechanism, functionality, modeling and applications. Progress in Polymer Science. 2012;37:1720-63.
[10] Fallah A, Saleem Q, Koc B. Assessment of mechanical properties and shape memory behavior of 4D printed continuous fiber-reinforced PETG composites. Composites Part A: Applied Science and Manufacturing. 2024;181:108165.
[11] Fallah A, Asif S, Gokcer G, Koc B. 4D printing of continuous fiber-reinforced electroactive smart composites by coaxial additive manufacturing. Composite Structures. 2023;316:117034.
[12] Functional polymers. 1 ed. Cham: Springer Cham, 2019.
[13] Wagermaier W, Kratz K, Heuchel M, Lendlein A. Characterization methods for shape-memory polymers. In: Lendlein A, editor. Shape-Memory Polymers. Berlin, Heidelberg: Springer Berlin Heidelberg; 2010. 97-145.
[14] Mehrpouya M, Huang WM. 11 - Origami-inspired 4D printing. In: Bodaghi M, Zolfagharian ABT-SMiAM, editors. Additive Manufacturing Materials and Technologies: Elsevier; 2022. 373-94.
[15] Sava ȘD, Pricop B, Comăneci RI, Cimpoeșu N, Popa M, Lohan NM, et al. Variations in the thermomechanical and structural properties during the cooling of shape-memory R-PETG. Polymers. 2024;16.
[16] Winkler S. Recycling For Dummies: Wiley, 2023.
[17] Nikolaev AA. The Physical Characterization and Terminal Velocities of Aluminium, Iron and Plastic Bottle Caps in a Water Environment. Recycling. 2022;7.
[18] Cersoli T, Cresanto A, Herberger C, MacDonald E, Cortes P. 3D Printed Shape Memory Polymers Produced via Direct Pellet Extrusion. Micromachines (Basel). 2021;12.
[19] Gao H, Li J, Zhang F, Liu Y, Leng J. The research status and challenges of shape memory polymer-based flexible electronics. Materials Horizons. 2019;6:931-44.
[20] Shape memory polymers, blends and composites: Advances and applications. Singapore: Springer Singapore, 2020.
[21] Lendlein A, Langer R. Biodegradable, elastic shape-memory polymers for potential biomedical applications. Science. 2002;296:1673-6.
[22] Behl M, Lendlein A. Shape-memory polymers. Materials Today. 2007;10:20-8.
[23] Ducheyne P. Comprehensive biomaterials. Elsevier Science. 2011.
[24] McGinty S. A decade of modelling drug release from arterial stents. Mathematical Biosciences. 2014;257:80-90.
[25] Lan X, Liu Y, Lv H, Wang X, Leng J, Du S. Fiber reinforced shape-memory polymer composite and its application in a deployable hinge. Smart Materials and Structures. 2009;18:024002.
[26] Mirasadi K, Rahmatabadi D, Ghasemi I, Khodaei M, Baniassadi M, Baghani M. Investigating the effect of ABS on the mechanical Properties, morphology, printability, and 4D printing of PETG‐ABS blends. Macromolecular Materials and Engineering. 2024;309:1-11.
[27] Li G, Wang A. Cold, warm, and hot programming of shape memory polymers. Journal of Polymer Science Part B: Polymer Physics. 2016;54:1319-39.
[28] Soleyman E, Rahmatabadi D, Soltanmohammadi K, Aberoumand M, Ghasemi I, Abrinia K, et al. Shape memory performance of PETG 4D printed parts under compression in cold, warm, and hot programming. Smart Materials and Structures. 2022;31.
[29] Bodaghi M, Serjouei A, Zolfagharian A, Fotouhi M, Rahman H, Durand D. Reversible energy absorbing meta-sandwiches by FDM 4D printing. International Journal of Mechanical Sciences. 2020;173:105451.
[30] Mobarakian M, Safarabadi M, Farahani M. Developing a thermomechanical and thermochemical model for investigating the cooling rate effects on the distortion of unsymmetrical viscoelastic polymeric composite laminates. Polymer Testing. 2020;87.
[31] Mobarakian M, Safarabadi M, Farahani M. Investigating the effects of cooling rate on distortion of asymmetric composite laminates. Composite Structures. 2020;236.
[32] Jafarpour A, Safarabadi Farahani M, Haghighi-Yazdi M. Numerical investigation of oriented CNFs effects on thermo-mechanical properties and curing residual stresses field of polymeric nanocomposites. Mechanics of Materials. 2019;138.
[33] Jafarpour A, Safarabadi M, Haghighi-Yazdi M, Yousefi A. Numerical study of curing thermal residual stresses in GF/CNF/epoxy nanocomposite using a random generator model. Mechanics of Advanced Materials and Structures. 2020;28:2618-28.
[34] Barletta M, Aversa C, Puopolo M, Vesco S. Extrusion blow molding of environmentally friendly bottles in biodegradable polyesters blends. Polymer Testing. 2019;77.
[35] Digikala. www.digikala.com. accessed: 2026.01.01 (in Persian).
Mechanic of Advanced and Smart Materials
Volume 5, Issue 3
Autumn 2025
Pages 421-436

  • Receive Date 05 May 2026
  • Revise Date 01 June 2026
  • Accept Date 02 August 2026

Home

Guide for Authors

Submit Manuscript

Contact Us