Carbon fibre–reinforced thermoplastics are attractive for lightweight applications due to their high strength and corrosion resistance. Among engineering polymers, polyamide 12 (PA12) is widely used due to its low moisture absorption; however, its relatively high cost and limited availability are drawbacks. Compatibilised blends based on high-density polyethylene (HDPE) and polyamide 6 (PA6) emerge as an alternative. This study comparatively evaluates PA12- and HDPE/PA6(50/50)-based formulations, reinforced and unreinforced with 10 wt.% carbon fibres, focusing on their mechanical, thermal, morphological, and rheological behaviour. The HDPE/PA6/carbon composite showed higher tensile strength (47.3 MPa) and modulus (2010 MPa), whereas PA12 composites exhibited greater ductility (elongation >190%). Carbon fibre incorporation increased stiffness and reduced melt flow in both systems. Thermal analyses indicated distinct crystallisation behaviours, with PA12 showing a more uniform crystalline structure, while HDPE/PA6 blends exhibited multiphase crystallisation due to their immiscible morphology. Overall, compatibilised HDPE/PA6 blends achieved mechanical performance comparable to or exceeding PA12, albeit with reduced ductility.
RajakDKWaghPHLinulE. Manufacturing technologies of carbon/glass fiber-reinforced polymer composites and their properties: a review. Polymers (Basel)2021; 13. DOI: https://doi.org/10.3390/polym13213721.
2.
DongWYuZSunX, et al.Carbon fiber-reinforced polyamide 6 composites: impact of fiber type and concentration on the mechanical properties. Materials (Basel)2025; 18. DOI: https://doi.org/10.3390/ma18071413.
3.
de ToroEVSobrinoJCMartínezAM, et al.Investigation of a short carbon fibre-reinforced polyamide and comparison of two manufacturing processes: fused deposition modelling (FDM) and polymer injection moulding (PIM). Materials (Basel)2020; 13. DOI: https://doi.org/10.3390/ma13030672.
4.
IshidaOOdaSUzawaK. Impregnation process of large-tow carbon-fiber woven fabric/polyamide 6 composites using solvent method. Compos Part A Appl Sci Manuf2024; 180. DOI: https://doi.org/10.1016/j.compositesa.2024.108068.
5.
BaniasadiHÄkräsLPaganelliZ, et al.Can biochar fillers advance the properties of composites? Early-stage characterization and life cycle assessment of novel polyamide/biochar biocomposites. Environ Res2025; 275. DOI: https://doi.org/10.1016/j.envres.2025.121446.
6.
KohutiarMKakošováLKrbataM, et al.Comprehensive review: technological approaches. Properties, and applications of pure and reinforced polyamide 6 (PA6), and polyamide 12 (PA12) composite materials. Polymers2025; 17. DOI: https://doi.org/10.3390/polym17040442.
7.
VijayanDSSivasuriyanADevarajanP, et al.Carbon fibre-reinforced polymer (CFRP) composites in civil engineering application—a comprehensive review. Buildings2023; 13. DOI: https://doi.org/10.3390/buildings13061509.
8.
AmjadiMFatemiA. Tensile behavior of high-density polyethylene including the effects of processing technique, thickness, temperature, and strain rate. Polymers (Basel)2020; 12. DOI: https://doi.org/10.3390/POLYM12091857.
9.
ChenLLinZ. Polyethylene: properties, production and applications. In: 2021 3rd International Academic Exchange Conference on Science and Technology Innovation, IAECST 2021, 2021, pp.1191–1196: Institute of Electrical and Electronics Engineers Inc.
10.
AgrawalPRodriguesAWBAraújoEM, et al.Influence of reactive compatibilizers on the rheometrical and mechanical properties of PA6/LDPE and PA6/HDPE blends. J Mater Sci2010; 45: 496–502.
11.
FengJZhangGMacInnisK, et al.Effect of compatibilizer on morphology and properties of HDPE/nylon 6 blends. J Polym Sci B Polym Phys2019; 57: 281–290.
12.
LiaoGLiZChengY, et al.Properties of oriented carbon fiber/polyamide 12 composite parts fabricated by fused deposition modeling. Mater Des2018; 139: 283–292.
13.
WuS-HWangF-YMaC-CM, et al.Mechanical, thermal and morphological properties of glass fiber and carbon fiber reinforced polyamide-6 and polyamide-6rclay nanocomposites. Mater Lett2001; 49: 327–333.
14.
Gulgunje PVNewcombBAGuptaK, et al.Low-density and high-modulus carbon fibers from polyacrylonitrile with honeycomb structure. Carbon N Y2015; 95: 710–714.
15.
ElkolaliMNogueiraLPRønningPO, et al.Void content determination of carbon fiber reinforced polymers: a comparison between destructive and non-destructive methods. Polymers (Basel)2022; 14. DOI: https://doi.org/10.3390/polym14061212.
16.
García-FonteXAres-PernasACerecedoC, et al.Influence of phase morphology on the rheology and thermal conductivity of HDPE/PA6 immiscible blends with alumina whiskers. Polym Test2018; 71: 56–64.
17.
DengRRenLSuD, et al.Nylon 12 composite powder prepared by thermally induced phase separation for selective laser sintering. J Mater Res2024; 39: 2482–2492.
18.
SanjaniNSAlipourANikfarjamN. Study of morphology and physical-mechanical properties of HDPE/PA6 and HDPE-g-MAH/PA6 nanocomposites with two types of 30B and 15A nanoparticles prepared via melt compounding. Polym Plast Technol Eng2013; 52: 1343–1352.
19.
DouRWangWZhouY, et al.Crystallisation behaviour of HDPE in PA6/EPDM-g-MA/HDPE ternary blend with different phase morphology. Plast, Rubber Compos2016; 45: 207–215.
20.
Ornaghi JrHLLazzariLKKercheEF, et al. Dynamic mechanical behavior of polymer nanocomposites. In: AbdellaouiHRangappaSMSiengchinS (eds) Mechanics of nanomaterials and polymer nanocomposites. Singapore: Springer, 2023. Epub ahead of print 2023. DOI: 10.1007/978-981-99-2352-6_8.
21.
AriABayramAKarahanM, et al.Comparison of the mechanical properties of chopped glass, carbon, and aramid fiber reinforced polypropylene. Polym Polym Compos2022; 30: 1–13.
KuleyinHGümrükRÇalışkanS. Fatigue behavior of polymethyl methacrylate/acrylonitrile butadiene styrene blends including blend composition, stress ratio, frequency, and holding pressure effects. Int J Fatigue2024; 187. DOI: https://doi.org/10.1016/j.ijfatigue.2024.108483.
25.
QiaoJZhangQWuC, et al.Effects of fiber volume fraction and length on the mechanical properties of milled glass fiber/polyurea composites. Polymers (Basel)2022; 14. DOI: https://doi.org/10.3390/polym14153080.
26.
OrnaghiHLNevesRMMonticeliFM, et al.Modeling of dynamic mechanical curves of kenaf/polyester composites using surface response methodology. J Appl Polym Sci2022; 139. DOI: https://doi.org/10.1002/app.52078.
27.
Rengaraj JSMVKKannanS, et al.Effect of fiber orientations on dynamic mechanical and machinability behavior of flax polymer composites. Proc Inst Mech Eng C J Mech Eng Sci2025; 239: 9257–9270.
28.
WagnerMHHirschbergV. Rheology of poly(α-olefin) bottlebrushes: effect of self-dilution by alkane side chains. Macromolecules2024; 57: 2110–2118.
29.
AstarakiSZamaniEMoghadamM, et al.Investigating the effect of temperature, angular frequency, and strain on the rheological properties of shear thickening fluid (STF) with different weight fractions of fumed silica. Colloid Polym Sci2024; 302: 1–11.
30.
MahmoudMHuitorelBFallA. Rheology and agglomeration behavior of semi-crystalline polyamide powders for selective laser sintering: a comparative study of PA11 and PA12 formulations. Powder Technol2024; 433. DOI: https://doi.org/10.1016/j.powtec.2023.119279.
31.
LunaCBBNogueiraJA dos Sda SilvaFS, et al.Exploring the selective distribution of PE-g-AA in the PA6/AES blend: rheological, mechanical, thermal, thermomechanical properties, and morphology. Polym Adv Technol2025; 36. DOI: https://doi.org/10.1002/pat.70275.
32.
KhaliliRJafariSHSaebMR, et al.Toward in situ compatibilization of polyolefin ternary blends through morphological manipulations. Macromol Mater Eng2014; 299: 1197–1212.
33.
JúniorHLODucheminBAzzayeS, et al.Radiopaque polyurethanes containing barium sulfate: a survey on thermal, rheological. Physical, and Structural Properties. Polymers (Basel)2024; 16. DOI: https://doi.org/10.3390/polym16213086.
34.
PêFR. RodriguesTACSda CunhaRB, et al.PLA/CB and HDPE/CB conductive polymer composites: effect of polymer matrix structure on the rheological and electrical percolation threshold. Polym Eng Sci2024; 64: 6014–6030.
35.
RamliHZainalNFAHessM, et al.Basic principle and good practices of rheology for polymers for teachers and beginners. Chemistry Teacher International2022; 4: 307–326.
36.
AgrawalPAraújoAPMLimaJCC, et al. Rheology, mechanical properties and morphology of poly(lactic acid)/ethylene vinyl acetate blends. J Polym Environ2019; 27: 1439–1448.
