Optimising Crystallisation during Rapid Prototyping of Fe₃O₄-PA6 Polymer Nanocomposite Component

Round 1

Reviewer 1 Report

The manuscript entitled "Optimising Crystallisation during Rapid Prototyping of Fe₃O₄-PA6 Polymer Nanocomposite Component" is in the scope of this Journal. However, this manuscript should be resubmitted for review subject to revisions and corrections based on the following comments and suggestions:

 

1. This study deals with the variation in the degree of crystallinity and crystallite size induced by nanoparticles since they can affect the melting temperature as well as the mechanical strength after testing for applications like stimuli-based self-healing.

It is also indicated in the introduction part that in many instances, the required concentration of the nanoparticles and their size can unfavourably change the degree of crystallinity of the PMC resulting into the hard and stiff polymer that cannot be formed into a flexible component. However the authors maintain the concentration of iron oxide nanoparticles constant at 1 wt% in their study by varying catalyst and activator during the in-situ polymerization. My question is if the authors could make a comment about the crystallisation process during anionic polymerisation if the study was performed in the absence of iron oxide nanoparticles or in the case that the presence of iron oxide nanoparticles was higher.

 

2. The authors wrote: “As for the glass transition peak, its associated temperature is increased gradually with the increase in the proportion of EtMgBr between 10% and 50%. Though there is a high possibility that the peak observed at around 50-60 °C can be ascribed to the melting out of the unreacted monomer. Especially, the distinguishingly huge peak at 57.36 °C for 10% sample suggests that most monomers were unreacted in this case, and the melting peak for this sample is barely visible in Figure 3 (a) (b) and (c).”

This statement is not clearly understandable, I do not understand which melting peak is barely visible in Figure 3 (a) (b) and (c).

Moreover, is it possible to perform a DSC for the monomer to confirm that the peak observed at 50-60 ^oC really belongs to the unreacted monomer?

 

3. Regarding Figure 3, most of the thermograms exhibit an asymmetric melting endotherm or even a quite well defined double melting (figure 3b 10% and 30% NACL), could you explain the presence of these double peaks?

 

4. Please check figure 4(a) and 4 (b). They seem to be the same and there is no correlation between the figures and the text.

 

5. Normalization of the FTIR spectra using an internal peak should be achieved, as some conclusions written by the authors may not be so. As for the case of the spectrum corresponding to 100% NACL in figure 5 (a).

 

6. The authors also suggest “Disappearance of peak at 3084 cm^-1 is seen to be related to less stretching of bond in absence of long polymer chains.” I disagree with the authors. The peak at 3084 cm^-1 is perfectly seen in all spectra regarding figure 5 (b) and even 5 (c).

 

7. So the following assessment should be reconsidered “The NACL provides more chain initiation sites leading to rapid chain formation but of short length. The sample with 100% NACL proportion, also had noteworthy concentration of NACL remaining as unreacted, because of unbalanced mixtures resulting from rapid polymerisation of the top surface monomer+EtMgBr solutions.”

 

8. The ATR spectrum of a commercial PA6 should be presented for comparison.

 

9. Regarding the figures corresponding to XRD measurements:

• “In 100% EtMgBr sample, other peaks are appearing showing additional phases with lower Bragg angles. The minor peaks observed at 17° 2θ, 22° 2θ and 28° 2θ can be identified as the γ -phase of the of PA6 with the corresponding miller indices of (020), (001) and (200)/(201) (29)” This is not discernible in figure 6(a)
• “As seen in Figure 6(c), the PA6 characteristic XRD reflection peaks at two Bragg angles display the multiphase formation for samples having 10% and 30% EtMgBr & NACL proportion.” This is not seen for sample 30% EtMgBr & NACL proportion

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,  

the manuscript presents interesting results about Fe₃O₄-PA6 polymer nanocomposites preparation procedure, characterization and properties.

Despite this, an improvement of the manuscript must be done.

There is a lack of information in some sections of the manuscript. Here are the suggestions and the questions: 

1. Please, write the equation for the performed anionic polymerization of ε-caprolactam monomer.
2. Add the information of the polymerization duration to the experimental section.
3. How the degree of polymerization was determined? What conversion of monomer to polymer is obtained?
4. Have you determined the quantity of the remained monomer in composite samples?
5. Please, add the information about the atmosphere during thermogravimetric measurements. Were the measurements carried out in nitrogen or air atmosphere?

 

Best regards

Author Response

Reply file Attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have addressed the majority of my concerns satisfactorily,  the paper can be now accepted for publication