F. Ronkay

10041328900

Publications - 8

Impact of recycling on polymer binder integrity in metal injection molding

F. Ronkay Zoltán Weltsch György Ledniczky Pál Hansághy

Publication Name: Scientific Reports

Publication Date: 2025-12-01

Volume: 15

Issue: 1

Page Range: Unknown

Description:

Metal Injection Molding (MIM) is a manufacturing process that integrates polymer binders with metal powders to produce high-precision components, offering both material efficiency and design flexibility. This study explores the recyclability of polymer-based feedstocks used in Metal Injection Molding, specifically evaluating how repeated recycling affects the structural integrity and thermal stability of polymer binders. Given the high cost of raw materials in MIM, optimizing recyclability is essential for reducing production costs and minimizing material waste, contributing to more sustainable manufacturing practices. To assess the feasibility of repeated material reuse, the study systematically subjected molded specimens to grinding and reinjection molding over eight consecutive cycles. The effects of reprocessing were analyzed using melt flow index (MFI) measurements, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) to track changes in polymer viscosity, thermal behavior, and degradation. The results indicate that wax precipitation during processing alters polymer viscosity and thermal stability, leading to gradual material property changes over successive recycling cycles. However, polymer degradation-induced viscosity reduction counterbalances these effects up to the fourth cycle, ensuring processability within standard injection molding conditions. The findings underscore the significance of analytical techniques in evaluating polymer binder integrity during multi-cycle reuse. Melt flow index (MFI) initially increased, peaking at the fourth recycling cycle, and then declined, while linear shrinkage rose by approximately 3% within the first three cycles before stabilizing. SEM–EDS analyses indicated around a 20% wax loss after multiple recycling cycles, significantly influencing binder rheology. Polymer binders can thus be successfully recycled up to four times while maintaining acceptable thermal and rheological properties, supporting resource-efficient and sustainable manufacturing strategies in MIM production.

Open Access: Yes

DOI: 10.1038/s41598-025-05577-x

Thermal, thermomechanical and structural properties of recycled polyethylene terephthalate (rPET)/waste marble dust composites

F. Ronkay László Lendvai Tej Singh

Publication Name: Heliyon

Publication Date: 2024-02-15

Volume: 10

Issue: 3

Page Range: Unknown

Description:

The main objective of this work is to review the capability of using waste marble dust (MD) particles as reinforcing materials in recycled polymeric composites to achieve environmentally friendly materials. In the present study, polymer composites were fabricated from recycled polyethylene terephthalate (rPET) and MD and then analyzed for their structural and thermal properties. Preparation of rPET-based composites containing 0–20 wt% MD was carried out through extrusion and injection molding. For their characterization Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) were applied. The DSC analysis revealed a nucleating effect of MD on rPET, which was manifested in a higher crystallization temperature (196.7 °C ⇒ 204.4 °C); however, the marble particles were also found to hamper chain mobility, thereby decreasing the crystallinity ratio (23.7 % ⇒ 19.2 %) of rPET and altering its crystalline structure. According to the TGA measurements, a slight increase occurred in the thermal stability of rPET, its major decomposition temperature increased from 446 °C to 451 °C when 20 wt% MD was incorporated into it. DMA showed an improved stiffness in the entire investigated temperature range for MD-filled composites versus neat rPET. Additionally, several factors were derived from the DMA data, including the effectiveness factor, degree of entanglement, and reinforcing efficiency factor which all suggested a decent interaction between the components indicating a proper reinforcing ability of marble powder. However, above 5 wt% MD content the reinforcing efficiency deteriorated due to the agglomeration of filler particles, which was also supported by scanning electron microscopic images.

Open Access: Yes

DOI: 10.1016/j.heliyon.2024.e25015

Development of Injection Moulded Electromagnetic Pulse Shielded Polymer Cover

F. Ronkay G. Dogossy

Publication Name: Advances in Transdisciplinary Engineering

Publication Date: 2024-01-01

Volume: 59

Issue: Unknown

Page Range: 186-193

Description:

Technology for an electromagnetic pulse shielded injection moulded product was developed, using in-mould metal mesh and a 3D printed spacer made of the same type of acrylonitrile-butadiene-styrene as the injection moulded polymer. The functional and mechanical properties of the manufactured flat and dumbbel specimens were tested. The metal mesh increased the stiffness of the plastic, decreased its Charpy impact strength, and did not significantly affect its tensile strength. Computed tomography scans confirmed that delamination and microcracking occur during the failure due to different elongation of the plastic and metal. The attenuation at 1 GHz was 16-19 dB, depending on the metal mesh used. The shielding properties were affected by the fact that the high pressure at the mould filling during the injection moulding process distorted the geometry of the metal mesh.

Open Access: Yes

DOI: 10.3233/ATDE240544

Experimental Investigation and Applicability of Multi-Stage Simulations in the Case of a Thick-Walled Injection-Moulded Composite

F. Ronkay Tamás Morauszki G. Dogossy

Publication Name: Applied Sciences Switzerland

Publication Date: 2022-09-01

Volume: 12

Issue: 17

Page Range: Unknown

Description:

The structure and mechanical properties of an injection-moulded short glass fibre (GF)-reinforced polymer composite were analysed through simulation methods. Fibre orientation, which evolves during the production of a thick-walled automotive part, was determined with an injection moulding simulation. Next, using the material model for the injected product, the force that resulted from the given deformation was determined with finite element software. To validate the simulation results, the examined products were manufactured with 30% reinforced GF, and then measurements were carried out. The validation of the fibre orientation tensor was achieved with optical microscope images, while the validation of the finite element, which analysed the flexural tests, was carried out through a comparison of flexural rigidity. The aim of the project was to verify the reliability of multi-stage finite element software. According to the results, in the case of a thick-walled GF-reinforced product, it was demonstrated that the integration of a different finite element software could be used reliably.

Open Access: Yes

DOI: 10.3390/app12178415

Development and characterization of composites produced from recycled polyethylene terephthalate and waste marble dust

F. Ronkay László Lendvai Vishal Ahlawat Guangming Wang Sicong Zhang Shaofeng Guo Tej Singh

Publication Name: Polymer Composites

Publication Date: 2022-06-01

Volume: 43

Issue: 6

Page Range: 3951-3959

Description:

The current paper presents the results of a study on the processing and characterization of waste marble powder-reinforced recycled polyethylene terephthalate (rPET) composites. Samples with up to 20 wt% marble dust (MD) content were produced with twin-screw extrusion followed by injection molding. Subsequently, the morphological and mechanical features and the wear resistance of the developed composites were studied. In terms of mechanical properties, the incorporation of MD steadily improved both the tensile and flexural modulus of rPET, while the strength values showed an optimum at 2.5–5.0 wt%, depending on the mode of loading. Above the optimal MD concentration, the strength values deteriorated, however, even at maximum (20 wt%) marble content they were still similar to that of neat rPET, which proves the potential of utilizing waste MD in this specific polymer as filler material. The surface hardness of the fabricated samples also gradually improved with higher marble content, yet it came at the cost of impact toughness. The analysis of wear performance revealed an increasing resistance against wear up to 5.0 wt% filler loading, above which the dust particles got easily peeled off from the matrix, decreasing its efficiency.

Open Access: Yes

DOI: 10.1002/pc.26669

Highly toughened blends of poly(lactic acid) (PLA) and natural rubber (NR) for FDM-based 3D printing applications: The effect of composition and infill pattern

F. Ronkay I. Fekete László Lendvai

Publication Name: Polymer Testing

Publication Date: 2021-07-01

Volume: 99

Issue: Unknown

Page Range: Unknown

Description:

In this study, the suitability of natural rubber (NR) toughened poly(lactic acid) (PLA)-based blends were investigated for additive manufacturing applications. Filaments for fused deposition modeling (FDM) were prepared with an NR concentration of 0 … 20 wt% using a twin-screw extruder. Subsequently, specimens were fabricated with a desktop 3D printer machine working on FDM principles. Besides the composition of PLA/NR blends, the effect of infill orientation was also analyzed by preparing two sets of specimens: i) one set prepared with an alternating raster angle of ±45° (3DGRID) and ii) another one with a linear infill parallel to the length of the specimens (3DPAR). Quasi-static and dynamic mechanical properties, morphology and thermal characteristics of the fabricated specimens were investigated. The tensile tests revealed that the presence of NR effectively enhances the ductility of PLA filaments, however, the achieved improvement was highly dependent on the applied infill pattern. Samples prepared using the 3DPAR infill exhibited an excellent deformability when paired with NR. On the other hand, the ones fabricated with the 3DGRID technique only showed a marginal improvement in elongation. Similarly, the Charpy impact tests indicated an outstanding impact resistance of NR-toughened 3DPAR specimens, while the 3DGRID types showed little to no improvement. Scanning electron microscopic analysis revealed a weaker interlayer adhesion in the specimens containing NR, which greatly contributed to the discrepancies observed between the mechanical properties of the samples prepared with different infill. The differential scanning calorimetry revealed an almost completely amorphous structure of 3D printed PLA due to the quite rapid cooling characteristic of the FDM technique, which was not affected by the embedded NR component.

Open Access: Yes

DOI: 10.1016/j.polymertesting.2021.107205

The effect of mold temperature on chemical foaming of injection molded recycled polyethylene-terephthalate

F. Ronkay Bela Molnar G. Dogossy

Publication Name: Thermochimica Acta

Publication Date: 2017-05-10

Volume: 651

Issue: Unknown

Page Range: 65-72

Description:

Foam injection molded samples were produced from recycled polyethylene-terephthalate using endothermic and exothermic foaming agents at different mold temperatures. The foam structure was analyzed by computer tomography and optical microscopy. The morphological properties of samples were analyzed by differential scanning calorimetry, using the three-phase model. Viscosities of the melts were changed during processing by endothermic and exothermic foaming agents, and as a result different foam structures were formed. Relationships between mold temperature and porosity were found. Morphologies of the samples made with different foaming agents were different, also due to the different cooling rates caused by the endothermic and exothermic foaming reactions.

Open Access: Yes

DOI: 10.1016/j.tca.2017.02.013

Investigation of mixing processes of polymer composites

F. Ronkay E. Sági G. Dogossy

Publication Name: Materials Science Forum

Publication Date: 2013-01-01

Volume: 729

Issue: Unknown

Page Range: 332-337

Description:

Three ultrahigh molecular weight polyethylene (UHMWPE) composites of differing composition, reinforced with multiwalled carbon nanotubes (MWCNT) were prepared. The homogeneous distribution of MWCNT has been attempted by two dry blending methods and one melt-mixing process. The efficiency of the various methods was characterized by their effects on the quasi-static and dynamic physical properties of the composites. In the case of composites manufactured by ball milling the effects of various adhesion promoter additives (compatibilizers) has also been studied by analyzing the tensile, flexural, Charpy impact and wear properties of the composites. © (2013) Trans Tech Publications, Switzerland.

Open Access: Yes

DOI: 10.4028/www.scientific.net/MSF.729.332