Laser Sintering of Nano-Graphite-Reinforced Polyamide Composites for Next-Generation Smart Materials: A Preliminary Investigation of Processability and Electromechanical Properties

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript explores the potential of laser sintering to fabricate nano-graphite-reinforced polyamide composites, focusing on both processability and electro-mechanical behavior. The topic is timely, especially given the growing interest in lightweight multifunctional materials for applications like fleible electronics and sensor-embedded polymers. The authors lay out a preliminary yet meaningful study that captures the early-stage feasibility of this composite system, covering SEM observations, conductivity shifts, and mechanical performance across varying filler contents.
Still, the work feels more exploratory than decisive in several key areas. The use of graphite as a reinforcing phase in polyamide matrices isn’t entirly novel, and this needs to be more openly addressed. What distinguishes this system, particularly the processing conditions or microstructural features, from previously explored graphite- or graphene-enhanced PA composites? The manuscript would benefit from a clearer framing of its novelty—possibly comparing how the proposed formulation and sintering strategy differ in print stability, percolation behavior, or thermal management from established studies.
The material limitations at higher filler contents, particulrly warping and poor interlayer bonding, are mentiond but not deeply examined. Could these deformations be tied to thermal conductivity mismatches or localized overheating during sintering? The discussion currently reads as observational rather than explanatory. Introducing a basic thermal model or referencing similar failure modes in other filled sintered systems would improve the depth. In some related studies, filler–matrix interfacial zones have been shown to dominate local stress transfer and thermal dissipation, which might be relevant here (doi:10.12989/sss.2020.25.2.183). Including even a brief comment on interfacial energy or diffusion barriers could be helpful.
The electrical conductivity data shows meaningful shifts with increasing graphite loading, but these values need context. How do they compare with percolation thresholds typically reported in graphite- or graphene-reinforced polymers? And how do they measure up to common requiremnts for electrostatic discharge or signal transmission applications? The authors could also clarify the structure of the conductive network—was any anisotropy observed, or is the conductivity relatively uniform? Prior research suggsts that beyond a certain threshold, the geometry and continuity of the filler network govern performance more than the filler content alone (doi:10.3390/app9245534).
In terms of mechanical testing, the general trend of reduced ductility at high filler levels is expected, but there’s not enough detail to evaluate repeatability. How many samples were tested for each graphite percentage? Were any standard deviations or error margins calculated? And were all failures tensile fractures within the gauge length, or did some samples fail prematurely due to defects or edge flaws? Clarifying this would not only bolster the credibility of the data but also give a more realistic picture of the process consistency.
When discussing printability, the authors mention warping and dimensional instability at high graphite content, which could stem from enhanced light absorption and thermal gradients. Could this be relatd to the optical and thermal behavior of the graphite itself? A recent study on graphite behavior in complex particulate environmnts demonstrated that the interaction of particle surface energy with applied thermal fields can shift processing thresholds. Similarly, work on Prediction of zinc, cadmium, and arsenic in European soils using multi-end machine learning models showed how subtle material variability can cause processing performance to drift in otherwise well-controlled environments.
The scalability question is left unanswered. Is the proposed formulation viable at an industrial scale using conventional SLS machines, or are the results highly dependent on lab-scale parameter tuning? And are the energy demands or powder recycling rates competitive with other conductive composite routes? This is a key consideration for any real-world deployment. Economic and process-efficiency comparisons from other material systems, such as in Effect of pumice powder and nano-clay on the strength and permeability of fiber-reinforced pervious concrete (doi:10.1016/j.conbuildmat.2021.122652), suggest that cost–performance tradeoffs should at least be acknowledged when presenting new material candidates.
A more detailed environmental or safety discussion would also be valuable. Handling fine graphite powders can pose inhalation risks, and process emissions or recyclability may impact long-term adoption. In materials development where additive manufacturing and sustainability intersect, it’s becoming increasingly expected that health and safety implications are considered. The work on Global and regional patterns of soil metal(loid) mobility and associated risks emphasizes how materials development intersects with broader ecological modeling frameworks—something that might be worth considering even in early-stage technical studies like this one.
From a presentation standpoint, the figures and tables are functional but could use some enhancement. SEM images would be more informative with added scale bars or higher- resolution insets, and legends on the mechanical and conductivity plots should be enlarged for clarity. The experimental section is detailed in some areas but leaves others vague—especially the graphite particle characteristics. Was any surface treatment applied? What was the particle size distribution, and how was mixing achieved to ensure dispersion? These are critical factors when dealing with filler-induced property changes.
Finally, the discussion would benefit from a more even-handed treatment of the results. While the material shows promise at modrate graphite contents, the performance plateau or decline at higher loadings needs to be addressed more thoroughly. Rather than focusing solely on the advantages, the authors could explore how tailoring filler geometry or using hybrid filler systems might overcome the brittleness observed. A related study, Enhanced prediction of occurrence forms of heavy metals in tailings: a systematic comparison of machine learning methods and model integration (doi:10.1007/s12613-025-3136-4), illustrates how complex input–output relationships can lead to nonlinear performance limits—an idea that might help in interpreting the mechanical behavior here.
In summary, the manuscript touches on an important material system and provides a meaningful early-stge look at how nano-graphite affects sintering and electro-mechanical behavior in polyamides. To bring the work up to publication level, the authors should refine the discussion around mechanisms, imprve statistical and comparative framing of their results, and better outline practical consideratons including environmental and scalability factors. Once expanded, this paper could offer a valuable contribution to the growing field of smart material manufacturing using powder-based additive methods.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper presents highly interesting results and is excellently prepared; however, several points require clarification.

The use of the term "smart materials" is not sufficiently justified. A more comprehensive introduction and a detailed discussion explaining this terminology should be included.

The compatibility between nano-graphite and polyamide should be addressed in the main text, as it is essential for understanding the material’s characteristics.

Additionally, it would be valuable to provide a more detailed explanation of the differences observed in the SEM images. The authors state that there is "a uniform and homogeneous incorporation of the nanofillers"; however, this claim is not clearly supported by the provided images. Visual indicators of these differences should be explicitly pointed out and discussed.

Author Response

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Reviewer 3 Report

Comments and Suggestions for Authors

This is an experimental paper on laser sintering of polyamide composites. There are some potentially useful results here, but they need to clarify which results are important.

 

Please define polyamide 12 as nylon-12 early in the manuscript.

 

Please explain the use of the obelus divide symbol in the second column of table 2, last two lines. I have no idea what is meant here as this is not common usage.

 

In figure 3, what are the units for the dimensions?

 

Please provide a better explanation for figure 4 in terms of the components.

In table 4, they cannot measure the temperature to two decimal places, especially based on figure 6. They can get one decimal place at best. What are the error bars on the temperature in table 4?

 

Add error bars to the bar chart on figure 7.

 

Figure 8. Please make the figure bigger and the colors more distinguishable as it is hard to see what they have done.

 

Line 326. The use of the obelus divide symbol makes no sense here. Same for line 331.

 

The error bars in table 5 are not consistent with the number of decimal places. Please make them consistent. I think that there are too many decimal places in most cases given the size of the error bars.

 

Line 388. The temperature is given to too many decimal places. Is a change of ~ 0.3 degrees C of any meaning given the error bars? They need to make a much stronger case that this change is important. It does not seem so to me. They suggest that the changes in temperature in the first bullet are not important. If so, then reduce what is said in this bullet in the conclusions. Please clarify what is important in the paper.

 

Please use paragraphs rather than bullet points in the conclusions and tie the results together so a reader can see what is important for applied science.

Author Response

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Author Response File: Author Response.pdf