Effect of Polynorbornene on Physico-Mechanical, Dynamic, and Dielectric Properties of Vulcanizates Based on Isoprene, α-Methylstyrene-Butadiene, and Nitrile-Butadiene Rubbers for Rail Fasteners Pads

Round 1

Reviewer 1 Report

Dear Authors,

I feel that the manuscript has been well presented. However, to improve upon the same I have suggested some minor modifications with some relevant questions. This is only to make the manuscript appear more complete.

Comments of the reviewer for the journal “Journal of Composite Science”

Title – Effect of Polynorbornene on, Dynamic 2 and Dielectric Properties of Vulcanizates Based on Isoprene, 3 α-Methylstyrene-Butadiene and Nitrile-Butadiene Rubbers for 4 Rail Fasteners Pads

Page	Section
01	Title	Instead of “Physical-Mechanical” I would rather ask to rewrite as “Physico-Mechanical” and this may be universally applied to every part of the text.
01	Abstract	The abstract section is reasonably well written.
01	Keywords	Appropriate, however, as stated earlier, it is better to write “physico-mechanical” instead of “physical-mechanical”
	Section 1. Introduction
02	line 52	State everything related to the specification of Norsorex in the same tense. If the product still exists then it is better to state the molecular weight and the glass transition temperature in the present tense. Also, state the type of molecular weight, i.e., the number average or the weight average. .
	Section 2. Experimental
03	line 103	The chemical name of TMQ should be mentioned.
03	line 119	The chemical name of the plasticiser, preferably in the IUPAC nomenclature is required to be mentioned, as you have mentioned the names of other chemicals, e.g., CBS.
03	line 133	It appears that you have forgotten to mention the sequential incorporation of other compounding ingredients such as the fillers, the anioxidants, the curatives. Please rewrite the whole section dealing with the preparation of the samples.
	line 134	The experimental stating the materials used describes the use of many other compounding ingredient. Maybe it is a mistake and so should be rewritten accordingly.
04	line 158	In this equation, you missed to place Vs, the molar volume of the solvent. Please rewrite the Flory-Rehner equation in the correct form by introducing Vs
04	line 156	Please also check the modified Flory Rehner equation where you have the Gerard Kraus equation because of the incorporation of the filler in high amount.  This is used for the calculation of the modified volume fraction of the rubber in the swollen mass of the rubber with the incorporated swelling solvent at equilibrium swelling condition. Otherwise the results may be erroneous.
04	line 181	The method of group contribution is appreciated. However, the use of a large amount of the plasticizer as is evident from Table 1 can affect the effectiveness of calculating the crosslink density using the Flory Rehner equation. The Flory Rehner equation is meant for much simpler crosslinked rubber systems.
	Section 3	It should be the “Results and Discussion” section instead of the wrongly written “Experimental” section. The previous section 2 is the “Experimental” part of the manuscript.
06	line 257	The curves in Figure 1.  show marching type of cure. On what basis you calculated the optimum cure time.
08	line 307	Both the TG analyses curves show some residual content, for RC it is 3.3 % and for PNB it is 5.7 % Can you account for the residues?
13	4. Conclusions	Well written.
13	References	The references seem to be relevant.

 

So far as the wuality of English language is concerned, I should say that it is good. Of course there is ground to further improve upon the existing one but this is not a must 

Author Response

The response is in the file attached.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

The paper presented herein is reflecting a deep understanding of physical and chemical properties displayed by polymers dedicated to target applications. Rubber is one of the most common plastic materials and its involvement in transport field is undoubtedly irreplaceable.

I would like to suggest some minor modifications to your manuscript, namely:

1.     In the abstract section please explain significance of the term “phr”.

2.     Table 3: Bottom explanation of the significance of the values: υ_r, M_c……

3.     Row 276 Please rephrase: “Table 3 data confirm the above assumption…”

4.     Row 299. Please rephrase: “Figure 3 displays that TGA…”

5.     Row 317. Please rephrase: “Data in table 4 shows that vulcanized…”

6.     Row 322. Please rephrase the paragraph, “due to” is repeating.

7.     Row 377. Delete the parenthesis at the end of the row.

8.     Paragraph 3.5. Please explain the significance of the provided data to the dielectric properties of the rubbers.

9.     Figures 6-8. Explain the notation of the parameters placed on vertical axis (maybe in the caption…).

Wishing you all the best,

Good English quality. I have suggested some minor modifications.

Author Response

The response is in the file attached.

Reviewer 2

1. In the abstract section please explain significance of the term “phr”.

 

Response:

The explanation was added.The abstract explains the meaning of the term “phr”. «It was found that vulcanized rubber, containing 24.0 phr (parts per hundred parts of rubber) PNB as part of the RC is characterized …»

2. Table 3: Bottom explanation of the significance of the values: υ_r, M_c……

 

Response:

The designations of the following symbols are given (ν_r, M_c, ν_c) in the notation of Table 3.

 

3. Row 276 Please rephrase: “Table 3 data confirm the above assumption…”

 

Response:

The changes have been made.

4. Row 299. Please rephrase: “Figure 3 displays that TGA…”

 

Response:

The changes have been made.

 

5. Row 317. Please rephrase: “Data in table 4 shows that vulcanized…”

 

Response:

The changes have been made.

 

6. Row 322. Please rephrase the paragraph, “due to” is repeating.

 

Response:

The changes have been made.

 

7. Row 377. Delete the parenthesis at the end of the row.

 

Response:

The changes have been made.

 

8. Paragraph 3.5. Please explain the significance of the provided data to the dielectric properties of the rubbers.

 

Response:

The changes have been made.

It should be noted that rail fastener spacers are used to prevent electrical current (electrical insulation) from traveling to adjacent rails. The electrical insulation between the rail fasteners and the absorption of vibration inevitably lead to heating of the material.

PNB has good physical characteristics, such as high thermal stability, low moisture absorption and low dielectric constant, which makes it attractive for the considered operating conditions.

The results of studies of the dielectric properties of vulcanizates indicate that with an increase in the concentration of PNB in the rubber mixture, the specific bulk electrical resistance increases and the tangent of the dielectric loss angle decreases, which characterizes the energy loss on the insulation. Since the heating of the material (rail pad), in particular, is associated with energy losses in the insulation, the described dielectric properties indicate that rail fastening pads will experience less heat during operation.

 

9. Figures 6-8. Explain the notation of the parameters placed on vertical axis (maybe in the caption…).

 

Response:

The changes have been made.

The text of the article provides explanations for the designations of parameters placed along the vertical axis in Figures 6-8. The sentence "In the course of studying the dielectric properties, the dependences of the capacitance (Fig. 6), specific volumetric electrical resistance (Fig. 7) and the dielectric loss tangent (Fig. 8) on temperature were obtained." replaced by "In the course of studying the dielectric properties, the dependences of the capacitance (C), specific bulk electrical resistance (ρ_V) and the dielectric loss tangent (tand) on temperature were obtained. Figures 6-8 show the temperature dependence curves of these indicators.”

 

Good English quality. I have suggested some minor modifications.

 

Response:

The English was checked and changes were made.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper investigates the impact of PNB on the physical-mechanical, dynamic, dielectric properties, and thermal behavior of vulcanizates, which combine isoprene, α-methylstyrene-butadiene, and nitrile-butadiene rubbers. The study reveals that vulcanized rubber incorporating 24.0 phr PNB as part of the RC demonstrates stable physical-mechanical properties, improved vibration-absorbing characteristics, and enhanced dielectric parameters. These findings suggest its potential as a suitable base for rail fasteners in railroad tracks. The overall quality of the study is commendable, but certain concepts require further elucidation. Addressing the following points would make the manuscript acceptable for publication:

 

a. Clarify the effect of adding PNB to Norman 747 LV RC in rubber compound compositions and provide an explanation of the underlying mechanism.

 

b. Provide a comparison between vulcanizates containing PNB and RC with those lacking PNB concerning physical-mechanical properties, dynamic and dielectric properties, as well as thermal behavior.

 

c. Elaborate on the implications for mechanical loss factor (tanδ) and storage modulus when increasing the content of RC, which includes PNB, in rubber compounds.

 

d. Specify the concentration at which vulcanized rubber with 24 phr PNB exhibits stable physical-mechanical properties, improved vibration-absorbing capabilities, and increased dielectric parameters.

 

e. While the authors mentioned the application of this new compound for rail fasteners, it is important to address other critical criteria such as tensile strength, fatigue, and aging. How do the authors consider and assess these issues in this study?

Author Response

Reviewer 3

 

1. Clarify the effect of adding PNB to Norman 747 LV RC in rubber compound compositions and provide an explanation of the underlying mechanism.

Response:

The introduction of powdered PNB into the rubber mixture is accompanied by its poor technological combination with the elastomeric matrix. This leads to a deterioration in the technological properties of the rubber compound during its manufacture and a decrease in the physico-mechanical properties of vulcanizates due to the appearance of PNB inclusions in the vulcanized rubber that are not combined with the rubber matrix. The effect of adding PNB to the Norman 747 LV plasticizer is manifested in the transfer of powdered PNB to an elastic state by obtaining a rubber-like composition.

 

1. Provide a comparison between vulcanizates containing PNB and RC with those lacking PNB concerning physical-mechanical properties, dynamic and dielectric properties, as well as thermal behavior.

 

The sentence "From the data in Table 4, It follows that vulcanizates containing RC had lower mod-ulus stress at 100%, tensile strength, hardness and tear resistance compared to the vulcanizate of the PB-1 sample." changed to "From the data in Table 4, It follows that vulcanizates containing RC had lower modulus stress at 100%, tensile strength, hardness and tear resistance compared to the vulcanizate of the PB-1 sample (for the vulcanizate PB-5, compared with the first PB-1, there is a decrease in the modulus stress at 100% elongation by 46.7%, tensile strength by 13.6%, hardness by 17.6% and tear resistance by 20, 4%).".

The sentence "In this case, there is an increase in the elongation at break, the RSC, and the abrasion of the vulcanizates." replaced by "In this case, there is an increase in the elongation at break, the RSC, and the abrasion of the vulcanizates (the PB-5 vulcanizate is characterized by an increase in the elongation at break by 79.2%, the RSC by 6.3 %, and the abrasion by 24.4% compared to the vulcanizate that does not contain the RC composition)."

It should be noted that the vulcanizate PB-5 compared to PB-1 is characterized by a decrease in the dielectric loss tangent at the minimum temperature (–70 °C) by 316.4%, and at the maximum temperature (100 °C) by 149.8%.

 

1. Elaborate on the implications for mechanical loss factor (tanδ) and storage modulus when increasing the content of RC, which includes PNB, in rubber compounds.

Response:

A further increase in the composition of the RС in the composition of the rubber compound, and, consequently, the PNB, probably leads to an increase in the peak maximum related to the PNB phase and the value of tanδ_max, as well as a decrease in the storage modulus E′, which improves the vibration damping properties of vulcanizates. However, an increase in the content of the RC composition in the rubber compound, apparently, will be accompanied by a decrease in the strength characteristics of vulcanizates due to an increase in the proportion of the Norman 747 LV plasticizer, which is part of the RC composition.

 

1. Specify the concentration at which vulcanized rubber with 24 phr PNB exhibits stable physical-mechanical properties, improved vibration-absorbing capabilities, and increased dielectric parameters.

Response:

The annotation and conclusions indicate the concentration of PNB contained in the composition of the rubber compound in the amount of 24.0 phr, at which the vulcanizates are characterized by stable physico-mechanical properties, improved vibration-absorbing properties and increased dielectric parameters. Section 2.2 also lists PNB concentrations in wt. %, corresponding in amounts of 6.0, 12.0, 18.0, 24.0 phr.

 

1. While the authors mentioned the application of this new compound for rail fasteners, it is important to address other critical criteria such as tensile strength, fatigue, and aging. How do the authors consider and assess these issues in this study?

 

Response:

We have the data we added to Supplementary materials.

“We have studied the performance properties of rubber, which are based on the study of their resistance to aggressive media. changes in the elastic-strength properties of vulcanizates after thermal aging in air and exposure to standard oil liquid SZhR-1 at a temperature of 100 ° C for 24 hours, as well as rubber mass after daily exposure to industrial oil I-20A, standard oil liquid SZhR-3 and water at room temperature.

The essence of the test method for the resistance of vulcanizates to thermal aging in air is that undeformed rubber samples are exposed to air at an elevated temperature (100 ° C) in a thermostat for 24 hours and the ability of rubbers to resist their effects is determined by changing the following indicators: conditional strength at tensile strength, relative elongation at break and hardness according to Shore A. The nominal tensile strength and relative elongation at break of vulcanizates before and after aging in air were determined on five samples in the form of double-sided blades with a thickness of (2.0 ± 0.2) mm. The test result was taken as the arithmetic mean of these indicators of five tested samples for each version of the vulcanizate before and after aging in air. The change in nominal tensile strength Δf_p (%) and relative elongation at break Δε_p (%) was calculated using formulas 1 and 2, respectively:

                                                                                       (1)

where  is the value of the conditional tensile strength before aging;   is the value of the conditional tensile strength after aging in air.

                                                                                      (2)

where  is the elongation at break before aging;  is the value of conditional tensile strength after aging in air.

The hardness before and after thermal aging in air was measured at three points in different places of the same sample in the form of a washer with parallel planes with a diameter of 50 mm and a thickness of 8 mm for each version of the vulcanizate. The change in hardness ∆H (unit Shore A) was calculated by formula 3:

                                                                                                          (3)

where H is the value of hardness before aging;  is the hardness value after aging in air.

The essence of the test method for the resistance of vulcanizates to the effects of a liquid aggressive environment is that rubber samples in an unstressed state are exposed to a liquid aggressive environment (standard oil liquid SZhR-1 with an aniline point of (124±1) °C, kinematic viscosity at 98.9 °C (20 ± 1) mm²/s) at a temperature of 100 °C in a thermostat for 24 hours and determine their resistance to the specified impact by changing the physical and mechanical properties: conditional tensile strength, relative elongation at break and Shore A hardness. The change in conditional tensile strength Δf_p (%), elongation at break Δε_p (%), and Shore A hardness (Shore A unit) of vulcanizates after their thermal exposure to SZhR-1 was calculated similarly using formulas 1-3, respectively.

The essence of the test method for the resistance of vulcanizates to the effects of liquid aggressive media is that rubber samples in an unstressed state are exposed to liquid aggressive media (industrial I-20A oils with a density at 20 °C of 0.89 g/cm³, kinematic viscosity at 40 °C 29-35 mm²/s; standard oil liquid SZhR-3 with an aniline point (70±1) °С, kinematic viscosity at 37.8 °С (33±1) mm²/s and water) at a temperature of 23 °С for 24 h and determine their resistance to the specified impact on the change in mass. The mass of vulcanizate samples before and after exposure to these aggressive media was determined on three rectangular samples with dimensions of 25×20 mm and a thickness of (2.0±0.2) mm. The test result was taken as the arithmetic mean of three tested samples for each variant of the vulcanizate before and after exposure to the indicated liquid aggressive media. Weight change ∆m (%) of vulcanizates was calculated by formula 4:

                                                                                       (4)

where  is the mass of the vulcanizate sample before exposure to aggressive media;  is the mass of the vulcanizate sample after soaking in aggressive environments.

The results of studies of the performance properties of vulcanizates are shown in the table.

 

Table. Performance properties of vulcanizates

Characteristics	Rubber compound options
	PB-1	PB-2	PB-3	PB-4	PB-5
Change in properties of vulcanizates after thermal aging in air at 100 °C for 24 hours
Δfp, %	-10.6±0.4	-10.3±0.4	-11.7±0.5	-12.5±0.5	-11.2±0.4
Δεp, %	-16.7±0.6	-18.4±0.7	-19.2±0.6	-15.4±0.6	-13.4±0.5
ΔH, a.u. Shore A	+3±1	+2±1	+2±1	+2±1	+2±1
Changes in properties of vulcanizates after exposure to SZhR-1 at 100 °C for 24 hours
Δfp, %	-23.2±0.9	-24.8±0.9	-21.6±0.8	-19.8±0.7	-18.6±0.7
Δεp, %	-15.5±0.6	-15.1±0.6	-13.4±0.5	-12.7±0.5	-11.3±0.4
ΔH, a.u. Shore A	-12±1	-10±1	-8±1	-7±1	-5±1
Change in the mass of vulcanizates after exposure to aggressive media at 23 °C for 24 hours
Δm (oil I-20A), %	5.54±0.08	5.03±0.07	4.60±0.07	4.12±0.06	3.79±0.05
Δm (SZhR-3), %	8.89±0.12	8.08±0.11	7.63±0.11	7.10±0.11	6.41±0.09
Δm (water), %	0.42±0.01	0.39±0.01	0.37±0.01	0.36±0.01	0.32±0.01

 

It follows from the table data that an increase in the content of RC, and, consequently, PNB, in the rubber mixture leads to a decrease in changes in the elastic-strength properties of vulcanizates after daily aging in air and exposure to SZhR-1 and their mass after exposure to industrial oil I-20A, SZhR-3 and water. The PB-5 vulcanizate is characterized by the least changes in these properties, which indicates its stability and its potential use as rail fasteners.”

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear Authors,

After going for the second review, I am happy to see that you have implemented most of the changes asked for.

You will find my comments in an attached word document.

Thanks for implementing the changes, and I wish you a nice day, 

Comments for author File: Comments.docx

Reviewer 2 Report

Dear Authors,

 

I am very pleased by the modifications you have performed.

Thank you!

Reviewer 3 Report

the revised version responses all my main concerns, it can be considered for acceptance.

fine