Experimental Study on Flexural Properties of Polyurethane–Cement Composites under Temperature Load

Round 1

Reviewer 1 Report

1.       Polyurethane cement composite is a new organic inorganic composite material with high 9 strength, corrosion resistance, a- Which is correct-Organic or inorganic?

2.       Abstract is very generic. It should be very specific to the manuscript including experimental results in a nut shell.

3.       Chemical composition of the silicate cement can be given.

4.       Description about the materials-WANNATE® PM-200 Isocyanate; (b) ES305 polyether polyol; (c) 200 Kosmos-29 Stannous Octoate; (d) HQEE chain extender are given. The specific utility or function for what it is used has to be given along with the specifications of the raw materials.

5.       The bending performance of polyurethane cement composites was studied by di- 448 rect bending test of small beams as the primary test method, and the specimen size 449 (length × width × height): was 250 mm × 30 mm × 35 mm- Is there any codal specification for the specimens. If so it has to be mentioned. On what basis this size was adopted?

6.       The behaviour of the sample as given in Figure-17 is explained but the reason behind the increase and decrease in the strength with reference to temperature to be explained with appropriate references.- Reason for decrease in strength with increase in temperature and vice versa.

7.       Compressive strength could also add value to the paper.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We sincerely appreciate the valuable comments you have made, which made us recognize our shortcomings and have the opportunity to improve our manuscript, the following content is our responses to your comments one by one.

 

Question 1: Polyurethane cement composite is a new organic inorganic composite material with high strength, corrosion resistance, a- Which is correct-Organic or inorganic?

Answer: Polyurethane cement composite is prepared by mixing organic material (polyurethane mastic) and inorganic material (cement). It has the properties of both organic and inorganic materials. The polyurethane as the matrix has toughness and corrosion resistance, and the cement as filler has good compressive properties. By mixing polyurethane and silicate cement, the composite performance can be complementary. Polyurethane cement is different from mortar or concrete, so it can be called organic-inorganic composite material. We have revised the wording of the manuscript to make it more reader-friendly and to avoid misunderstandings. We have revised " organic inorganic " to " organic-inorganic " throughout the manuscript.

 

Question 2: Abstract is very generic. It should be very specific to the manuscript including experimental results in a nut shell.

Answer: Thank you for this valuable feedback. Your comment is very helpful for us to improve the quality of the manuscript. We have taken your suggestion and revised the abstract carefully. We highly summarize the main experimental results, as " The test results showed that the tensile strength of polyurethane cement decreased first, then increased and finally decreased with the increase of temperature, while the bending stiffness modulus decreased with the increase of temperature "(line 15~line 19). In addition, we have revised the section on the content of the disruption model so that the reader has a clearer understanding of the content and results of our study from the abstract, as " the damage mode of the samples under different temperature loads was analyzed and the "L" type damage strain curve was obtained"(line 19~line 21).

 

Question 3: Chemical composition of the silicate cement can be given.

Answer: We thank the reviewer for making this suggestion. We have taken your suggestion and added relevant information on the chemical composition of silicate cement. We have added the information in Table 1.

Table 1. 42.5 Physical and mechanical properties of ordinary Silicate cement.

Serial number	Project	Index
1	Flexural strength /MPa	3 days	4.6
		28 days	10.5
2	Compressive strength /MPa	3 days	24.6
		28 days	55.6
3	Fineness /%	1.8
4	Loss on ignition /%	≤5.0
5	Clinker and gypsum mass ratio /%	≥80 and＜95
6	Specific surface area /(m2/kg)	≥300
7	Chemical composition/%	C3S	51
		C2S	25
		C3A	9
		C4AF	9
		Other	6

 

Question 4: Description about the materials-WANNATE^® PM-200 Isocyanate; (b) ES305 polyether polyol; (c) 200 Kosmos-29 Stannous Octoate; (d) HQEE chain extender are given. The specific utility or function for what it is used has to be given along with the specifications of the raw materials.

Answer: We sincerely appreciate the valuable comments. The main function of WANNATE^® PM-200 isocyanate, ES305 polyether polyol, Kosmos-29 Stannous Octoate, and HQEE chain extender is to synthesize polyurethane colloids, and how they are used is described in sections 2.1 and 3.1 of the manuscript. For a more detailed presentation, based on the reviewers' comments, we have also added in the revised manuscript a description of other uses of these four ingredients in different fields (line 168~line 171, line 180~line 183, line 192~line 194, line 207~line 209). The modifications are as follows：

1. WANNATE^®PM-200 isocyanate is one of the important raw materials for preparing polyurethane colloids. The isocyanate contains a large number of isocyanate groups, which constitute the soft chain segment in the molecular structure of polyurethane and determine the tensile strength of polyurethane.
2. ES305 polyether polyol is also an important raw material for synthesizing polyurethane colloid. Polyether polyols contain a large amount of hydroxyl (-OH), which is reducible. After polymerization, they form the hard chain segment in the molecular structure of polyurethane, which determines the relative molecular weight of polyurethane.
3. Kosmos-29 Stannous Octoate plays a catalytic role in the process of preparing polyurethane, promoting the polymerization reaction to proceed in the expected direction and speed, and can also enhance the viscosity of polyurethane.
4. HQEE chain extender can further extend the polyurethane molecular chain, generate linear molecules with larger molecular weight, and improve the flexibility of polyurethane colloid.

 

Question 5: The bending performance of polyurethane cement composites was studied by di- 448 rect bending test of small beams as the primary test method, and the specimen size 449 (length × width × height): was 250 mm × 30 mm × 35 mm- Is there any codal specification for the specimens. If so it has to be mentioned. On what basis this size was adopted?

Answer: Thanks for your suggestion. We have a theoretical basis for making (length × width × height) 250 mm × 30 mm × 35 mm specimens. Polyurethane cement is a high-tenacity composite material with higher tensile strength than ordinary concrete, and its physical properties are closer to those of asphalt mixtures. In order to ensure that the experimental results are closer to the actual situation, we designed the dimensions according to the technical requirements of the asphalt mixture bending test. We also added literature to the revised manuscript as the basis for adopting this dimension (line 482).

The specific literature cited is as follows：

48. JTG-E20-2011 Test Specification for Asphalt and Asphalt Mixture of Highway Engineering; Research Institute of Highway Science, M. of T., Ed.; People’s Communications Press: Beijing, China, 2011;

 

Question 6: The behaviour of the sample as given in Figure-17 is explained but the reason behind the increase and decrease in the strength with reference to temperature to be explained with appropriate references.- Reason for decrease in strength with increase in temperature and vice versa.

Answer: We think this is a good suggestion. We have considered your suggestion and added to the revised manuscript an explanation of the trend of the flexural strength of polyurethane cement with temperature from the perspective of the microscopic molecular structure. The molecular properties of polyurethane directly determine the flexural strength of polyurethane cement, while the temperature properties are mainly reflected in the glass transition temperature T_g of polyurethane, which is the reason why the inflection point would appear in Figure 17 of the original manuscript. Therefore, we added Table 9 to the revised manuscript to show the T_g of different types of polyurethane cement more visually. we also carefully reviewed a large amount of literature and cited the research-worthy parts of it to make our content more scientific and reliable. The modifications are as follows：

The figue is in the attached word file.

Figure 20. Flexural tensile strength of polyurethane cement at different temperature levels.

Polyurethane cement, as an organic-inorganic composite, has the properties of both organic polyurethane colloid and inorganic cement particles. The cement is mainly a crystalline structure formed by the coalescence of particles such as C2S and C3S, with a reticulated internal distribution, which mainly provides compressive strength. Polyurethane colloid is made of polyether polyol soft chain segments and isocyanate hard chain segments polymerized into a polymeric substance with long molecular chains and interwoven distribution of soft and hard chain segments, which has good tensile properties and directly determines the flexural strength of polyurethane cement. The principle of bending strength of polyurethane cement is explained from the microscopic molecular point of view. The soft chain segment of polyurethane colloid presents a rubbery state, which provides low temperature performance; the hard chain segment presents a glassy or semi-crystalline state, which provides high temperature performance [52]. Reflecting the temperature performance of polyurethane is mainly expressed in the glass transition temperature T_g, the magnitude of T_g depends on the binding force between macromolecules and the length of molecular chains, so the slender and soft chain segments have a more obvious effect on the T_g of polyurethane cement [53]. Table 8 lists the T_g of several common types of polyurethane colloids [54]. From the table, it can be seen that the T_g of MDI-PPG polyurethane colloid is -32°C. The glass transition of polyurethane will occur when the temperature increases to -32°C, which is consistent with the results shown in Figure 20, where the first inflection point occurs near -30°C. When the temperature is lower than -30°C, the polyurethane tends to a flexible rubbery state with an increase in bending strength, corresponding to the change in the interval from -50°C to -30°C in Figure 20. When the temperature is higher than -30°C, the molecules inside the polyurethane continuously absorb heat from the outside as the temperature rises, and the hydrogen bonding between molecules gradually strengthens, leading to another increase in bending strength [55]. This change is consistent with the results shown in the -30°C to 0°C interval in Figure 20. However, the change in bending strength with increasing temperature is not continuous. Due to the poor heat resistance of polyurethane, when the temperature is too high, the spacing between the soft and hard chain segments becomes smaller and smaller, limiting the intermolecular movement, and the polyurethane tends to soften, leading to a continuous decrease in bending strength. This is consistent with the results shown in the last interval in Figure 20.

Table 9. T_g of common polyurethane colloids.

Type	Tg/℃
MDI-BDO	-46℃
MDI-PPG	-32℃
TDI-BDO	-71℃
TDI-PPG	-48℃

 

References cited are as follows:

52. Li, C.; Wang, B.; Wen, X.; Shao, C.; Wang, D. Effect of Hard Segment Content on the Mechanical Properties of Polyurethane-Urea Elastomers. China Plast. Ind.2022, 50, 110–115.
53. Liu, B. Factors Influencing the Glass Transition Temperature of Polyurethane Elastomers. Polyurethane Ind.2003, 18, 5–9.
54. Yaohui Bian, Libang Feng, Zhengyang Yu, Xueting Shi, Y.W. Repair Behavior of Nanosized SiO2-Modified Thermally Reversible Self-Healing Polyurethane. Mater. Sci. Eng.2019, 35, 44–50, doi:10.16865/j.cnki.1 000-7555.2019.0129.
55. Zhao, P.; Wen, Q.; Wang, Y.; Zhu, J.; Hua, X. Infrared Spectroscopic Analysis of Hydrogen Bond in Gradient Cured Polyurethane Urea. Spectr. Anal.2008, 28, 551–554.

 

Question 7: Compressive strength could also add value to the paper.

Answer: We think this is a very good suggestion. In fact, we have already studied the compressive strength of polyurethane-cement composites and published a paper entitled "Study on fatigue test and life prediction of polyurethane-cement composite (PUC) under high or low temperature conditions". In that paper, we made a batch of compressive specimens of polyurethane cement with different ratios and carried out compressive tests to obtain the compressive strength and compressive modulus of elasticity of polyurethane cement. The focus of the study in this manuscript is to investigate the flexural strength of polyurethane cement under different temperature loads. We believe that the compressive strength of polyurethane cement composites is derived from the cement and the flexural strength is derived from the polyurethane colloid. In fact cement, as an inorganic material, the effect of temperature change on its mechanical strength is not obvious. On the contrary, polyurethane is a polymer material, and its strength mainly comes from internal intermolecular interactions, and the intermolecular forces are very sensitive to temperature changes. Combined with the experiments and analyses we have carried out, it is known that the change in temperature loading mainly affects the flexural strength of polyurethane cement. The compressive strength of polyurethane cement is not the focus of our research in this paper. We have also incorporated the reviewer's comments and added a section on the compressive strength of polyurethane cement at this 1:1 ratio (line 457~line 478). In this section, we describe the process of conducting compressive tests and obtaining stress-strain curves for the compressive strength of polyurethane cement at this ratio. The modifications in the manuscript are as follows：

The polyurethane cement specimen is prepared by mixing the polyurethane raw materials and Portland cement in a 1:1 mass ratio. In order to determine the compressive strength of the polyurethane cement mixture at this ratio, the compressive test was conducted before the bending test under temperature load. The compression test results are shown in Section 5.1.

5.1. Compression test

In order to determine the compressive strength of the polyurethane cement composite at this ratio, a compressive test was conducted before the bending test. The compressive strength test was performed using cubic specimens with a side length of 70 mm, and the specimen preparation process is shown in Figure 13.

The figue is in the attached word file.

Figure 13. Polyurethane cement compressive test pieces at 1:1 ratio (mm).

A total of three specimens were prepared for this test. After waiting for all the polyurethane cement compressive specimens to set, they were placed under the MTS universal testing machine for the compressive test, as shown in Figure 14. After the test, the compressive strength of this proportion of polyurethane cement was obtained, and the maximum compressive strength was 66.6 MPa, and the stress-strain curve was plotted as shown in Figure 15.

The figue is in the attached word file.

Figure 14. Polyurethane cement specimen pressure loading test.

The figue is in the attached word file.

Figure 15. Stress-strain curve of polyurethane and cement at a 1:1 ratio.

 

 

We tried our best to improve the manuscript and based on the reviewers' suggestions, we have marked the changes in yellow. In addition, in the revised manuscript, we made some minor adjustments, such as the figure number and the chapter order, and marked them in green; these changes do not affect the framework of the paper. We sincerely thank you for your enthusiastic work and hope that these changes will be recognized. Thank you again for your comments and suggestions.

 

 

Yours sincerely,

Hongshuai Gao

[email protected]

Author Response File: Author Response.docx

Reviewer 2 Report

What is the mix proportion of cement pastes or mortars for serial 1-12? Express it in kg/m3

Why was the compressive strength of composites not determined

Can we get the water absorption and porosity of composites

Here various temperature levels are used. Can you tabulate the experimental scheme in the table? In this way, readers would be able to comprehend the testing scheme. Please also mention no. of samples and sample size in the table.

Can you relate the strain-hardening behavior of composites with the stress-strain results at various temperatures? Also, present the plausible mechanism for this phenomenon

In general, I feel the figures belonging to experimental results are scarce in the paper. It can be compensated by drawing more figures from Table. 6

The author has emphasized the importance of polyurethane cement's chemical structure and mode of action. Hence, several figures have been added. I suggest the author club these numerous figures in few figures, and emphasis should be placed on the experimental results obtained. This way, the study would be less hypothetical and more realistic.

There are very few references in the results and discussion section. Hence, more references should be added.

Author Response

Dear Reviewer,

We sincerely appreciate the valuable comments you have made, which made us recognize our shortcomings and have the opportunity to improve our manuscript, the following content is our responses to your comments one by one.

 

Question 1: What is the mix proportion of cement pastes or mortars for serial 1-12? Express it in kg/m³

Answer: We sincerely appreciate the valuable comments. We prepared polyurethane cement composites by mixing polyurethane raw materials and silicate cement powder in a ratio of 1:1 by mass. The polyurethane raw materials used were made by the polymerization reaction of isocyanate, polyester polyol, catalyst, and chain extender in the mass ratio of 1:1:0.02:0.05. A total of 11 groups of polyurethane cement specimens were made, with the number of specimens in each group being no less than three. Based on the comments of the reviewers, the specific ratios of raw materials such as silicate cement were compiled and summarized in Table 6 using kg/m³ and added to the revised manuscript (line 397~line 399).

Table 6. The mix ratio of each raw material for this test(kg/m³)

Serial number		Raw materials	Mix ratio
1	PM-200 isocyanate		387
2	ES305 polyether polyol		387
3	Kosmos-29 catalyst		7.7
4	HQEE chain extender		19.3
5	Silicate cement		801

 

Question 2: Why was the compressive strength of composites not determined

Answer: We think this is a very good suggestion. In fact, we have already studied the compressive strength of polyurethane-cement composites and published a paper entitled "Study on fatigue test and life prediction of polyurethane-cement composite (PUC) under high or low temperature conditions". In that paper, we made a batch of compressive specimens of polyurethane cement with different ratios and carried out compressive tests to obtain the compressive strength and compressive modulus of elasticity of polyurethane cement. The focus of the study in this manuscript is to investigate the flexural strength of polyurethane cement under different temperature loads. We believe that the compressive strength of polyurethane cement composites is derived from the cement and the flexural strength is derived from the polyurethane colloid. In fact cement, as an inorganic material, the effect of temperature change on its mechanical strength is not obvious. On the contrary, polyurethane is a polymer material, and its strength mainly comes from internal intermolecular interactions, and the intermolecular forces are very sensitive to temperature changes. Combined with the experiments and analyses we have carried out, it is known that the change in temperature loading mainly affects the flexural strength of polyurethane cement. The compressive strength of polyurethane cement is not the focus of our research in this paper. We have also incorporated the reviewer's comments and added a section on the compressive strength of polyurethane cement at this 1:1 ratio (line 457~line 478). In this section, we describe the process of conducting compressive tests and obtaining stress-strain curves for the compressive strength of polyurethane cement at this ratio. The modifications in the manuscript are as follows：

The polyurethane cement specimen is prepared by mixing the polyurethane raw materials and Portland cement in a 1:1 mass ratio. In order to determine the compressive strength of the polyurethane cement mixture at this ratio, the compressive test was conducted before the bending test under temperature load. The compression test results are shown in Section 5.1.

5.1. Compression test

In order to determine the compressive strength of the polyurethane cement composite at this ratio, a compressive test was conducted before the bending test. The compressive strength test was performed using cubic specimens with a side length of 70 mm, and the specimen preparation process is shown in Figure 13.

The figure is in the attached word file.

Figure 13. Polyurethane cement compressive test pieces at 1:1 ratio (mm).

A total of three specimens were prepared for this test. After waiting for all the polyurethane cement compressive specimens to set, they were placed under the MTS universal testing machine for the compressive test, as shown in Figure 14. After the test, the compressive strength of this proportion of polyurethane cement was obtained, and the maximum compressive strength was 66.6 MPa, and the stress-strain curve was plotted as shown in Figure 15.

The figure is in the attached word file.

Figure 14. Polyurethane cement specimen pressure loading test.

The figure is in the attached word file.

Figure 15. Stress-strain curve of polyurethane and cement at a 1:1 ratio.

 

Question 3: Can we get the water absorption and porosity of composites

Answer: Thank you for your advice. Yes, we can get the water absorption and porosity of polyurethane cement composites, which is also the focus of our next research. Polyurethane is a polymer compound formed by the polymerization of isocyanate and polyether polyol. As described in lines 274~277 of this draft, isocyanate groups are highly active and will react with water molecules to produce a large amount of carbon dioxide gas. These carbon dioxide gases will remain in the polyurethane colloid, which is difficult to be discharged, forming tiny pores and affecting the mechanical properties of polyurethane cement composites. This paper mainly studies the flexural strength of polyurethane cement under temperature load. In order to avoid the influence of porosity on the strength of composite materials, we have carried out drying and dehydration treatment (line 416~line 420). The polyurethane cement composite obtained in this paper is a composite without internal bubbles, and the polyurethane cement formed is a dense homogeneous material. In fact, we are studying the water absorption of the polyurethane cement composite, and have carried out some experimental studies, such as porosity measurement by drainage method and optical measurement by SEM microscope. Because of time, these experimental results cannot be obtained temporarily. Of course, we also adopted your suggestion and added the information on the water content and porosity of the test sample (line 444~line 446). The revised contents are as follows:

The polyurethane cement sample prepared by drying the silicate cement has a smooth and flat surface and no bubbles or holes inside. It is a compact and uniform material, and its macroscopic water content and porosity are basically 0%.

Question 4: Here various temperature levels are used. Can you tabulate the experimental scheme in the table? In this way, readers would be able to comprehend the testing scheme. Please also mention no. of samples and sample size in the table.

Answer: We think this is an excellent suggestion. Following the reviewer's comments, we produced Table 7, which contains the number of samples at different temperatures and the dimensions of the samples. This can show our test protocol more clearly and facilitate the reader's understanding. We have added this table to the revised manuscript.

Table 7. Bending test protocol for polyurethane cement specimens at different temperatures

Group	T/℃	Length × Width × Height(mm)
PUC 0	-50℃	250×30×35
PUC 1	-40℃
PUC 2	-30℃
PUC 3	-20℃
PUC 4	-10℃
PUC 5	0℃
PUC 6	10℃
PUC 7	20℃
PUC 8	30℃
PUC 9	40℃
PUC 10	50℃

 

Question 5: Can you relate the strain-hardening behavior of composites with the stress-strain results at various temperatures? Also, present the plausible mechanism for this phenomenon

Answer: Thanks for your positive comments and valuable suggestions to improve the quality of our manuscript. We can give a corresponding interpretation of the stress-strain results of the composite at different temperatures. Polyurethane cement is an organic-inorganic composite material that combines the compressive properties of inorganic cement particles with the tensile properties of organic polyurethane colloids. This relationship is similar to the relationship between concrete and steel reinforcement in reinforced concrete structures. Polyurethane colloids are temperature-sensitive materials, and temperature changes affect the composition of the hydrogen bonds within the molecules, which in turn affects the mechanical properties of the polymer, a property that directly determines the bending strength and bending strain of polyurethane cement as a function of temperature. We have reinterpreted this phenomenon from a microscopic molecular perspective and added modifications to the revised manuscript (line 713~line 723). The revised contents are as follows：

The figure is in the attached word file.

Figure 21. Failure strain of polyurethane cement at different temperature levels.

Polyurethane is a polymer with a large number of polar bonds in the system, which can be divided into hard chain segments, hydrogen bonds between soft chain segments, and intra-molecular hydrogen bonds. When the temperature rises, the thermal movement of molecular chains intensifies, and the hydrogen bonds between soft and hard chain segments absorb a lot of energy and break gradually, forming internal molecular hydrogen bonds continuously [57,58]. At this time, the spacing between the polyurethane molecular chains keeps decreasing, and the polyurethane colloid tends to curl, which is macroscopically realized as the effective crosslink density of polyurethane cement composites decreases, the strain keeps increasing, and the elastic modulus gradually decreases. This is consistent with the trend of the increasing strain of damage with increasing temperature and decreasing modulus of elasticity expressed in Figure 21 and Figure 22.

References cited are as follows:

57. Zhu, H.; Yan, Z.; Xv, Q.; Hu, C. Effect of Activation Temperature on the Structure and Properties of One Component Waterborne Polyurethane Membranes. Acta Polym. Sin.2007, 892–896.
58. Chen, D.; Li, Y. Dynamic Mechanical Analysis of Hydrogen Bonding in Thermoplastic Polyurethane Elastomer. Chem. J. Chinese Univ.2001, 844–846.

 

 

Question 6: In general, I feel the figures belonging to experimental results are scarce in the paper. It can be compensated by drawing more figures from Table. 6

Answer: Thanks for your constructive suggestion, which is highly appreciated. Table 6 of the original manuscript contains information on the stress, strain, stiffness modulus, maximum load, and mid-span deflection at failure for the polyurethane cement composite at different temperatures. In order to reflect the test results, we have plotted the bending strength graph, bending strain variation graph, modulus of failure stiffness graph, load-displacement curve graph, and damage mode graph of the polyurethane cement specimens in the manuscript, and we have also added the stress-strain curve graph for the compressive test of the polyurethane cement composites. In the revised version, we increased the number of figures from 23 to 26. The information in these figures provides a detailed description of the experimental content of this study.

 

Question 7: The author has emphasized the importance of polyurethane cement's chemical structure and mode of action. Hence, several figures have been added. I suggest the author club these numerous figures in few figures, and emphasis should be placed on the experimental results obtained. This way, the study would be less hypothetical and more realistic.

Answer: Thank you for your valuable suggestions. Our paper attempts an innovative research approach to investigate polyurethane cement composites from different scales by combining microscopic models and macroscopic experiments, and can explain in more detail the reasons for the change in flexural strength of polyurethane cement under temperature loading. We analyzed and modeled the microphase separation structure, fractional wave state density, and energy band structure of polyurethane from a microscopic molecular perspective to explain the internal reaction mechanism of polyurethane cement, and conducted mechanical experiments to analyze the flexural strength, flexural strain, stiffness modulus, and damage mode of polyurethane cement composites under temperature loading. The chemical structure and mode of action of polyurethane cement is an important basis for the microscopic molecular perspective, and we have added these images to the original manuscript to make it easier for the reader to understand.

 

Question 8: There are very few references in the results and discussion section. Hence, more references should be added.

Answer: We sincerely appreciate the valuable comments. We have checked the literature carefully and added more references in the results and discussion section of our revised manuscript.

The cited literature is as follows:

1. Wang, J.; Zhang, C.; Deng, Y.; Zhang, P. A Review of Research on the Effect of Temperature on the Properties of Polyurethane Foams. Polymers (Basel). 2022, 14, 4586, doi:10.3390/polym14214586.
2. Cipriani, E.; Zanetti, M.; Brunella, V.; Costa, L.; Bracco, P. Thermoplastic Polyurethanes with Polycarbonate Soft Phase: Effect of Thermal Treatment on Phase Morphology. Polym. Degrad. Stab. 2012, 97, 1794–1800, doi:10.1016/j.polymdegradstab.2012.06.004.
3. Li, C.; Wang, B.; Wen, X.; Shao, C.; Wang, D. Effect of Hard Segment Content on the Mechanical Properties of Polyurethane-Urea Elastomers. China Plast. Ind. 2022, 50, 110–115.
4. Liu, B. Factors Influencing the Glass Transition Temperature of Polyurethane Elastomers. Polyurethane Ind. 2003, 18, 5–9.
5. Yaohui Bian, Libang Feng, Zhengyang Yu, Xueting Shi, Y.W. Repair Behavior of Nanosized SiO₂-Modified Thermally Reversible Self-Healing Polyurethane. Polym. Mater. Sci. Eng. 2019, 35, 44–50, doi:10.16865/j.cnki.1 000-7555.2019.0129.
6. Zhao, P.; Wen, Q.; Wang, Y.; Zhu, J.; Hua, X. Infrared Spectroscopic Analysis of Hydrogen Bond in Gradient Cured Polyurethane Urea. Spectrosc. Spectr. Anal. 2008, 28, 551–554.
7. Lei, J.; Feng, F.; Xu, S.; Wen, W.; He, X. Study on Mechanical Properties of Modified Polyurethane Concrete at Different Temperatures. Appl. Sci. 2022, 12, doi:10.3390/app12063184.
8. Zhu, H.; Yan, Z.; Xv, Q.; Hu, C. Effect of Activation Temperature on the Structure and Properties of One Component Waterborne Polyurethane Membranes. Acta Polym. Sin. 2007, 892–896.
9. Chen, D.; Li, Y. Dynamic Mechanical Analysis of Hydrogen Bonding in Thermoplastic Polyurethane Elastomer. Chem. J. Chinese Univ. 2001, 844–846.
10. Zhao, P.; Hu, F.; Huang, X. Effect of Gradient Temperature Field on the Degree of Polyurethane Microphase Separation. Eng. Plast. Appl. 2011, 39, 32–35.

 

We tried our best to improve the manuscript and based on the reviewers' suggestions, we have marked the changes in yellow. In addition, in the revised manuscript, we made some minor adjustments, such as the figure number and the chapter order, and marked them in green; these changes do not affect the framework of the paper. We sincerely thank you for your enthusiastic work and hope that these changes will be recognized. Thank you again for your comments and suggestions.

 

 

Yours sincerely,

Hongshuai Gao

[email protected]

 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

good response by the authors
just 
The values given in table-6 should be rounded off to nearest whole number for example...387 to 3.90, 7.7 to 7.5, 19.3 to 19 or 20, and 801 to 800.

give atleast 5 keywords and arrange them in alphabetical order 

Author Response

Dear Reviewer,

Thanks for your professional review work on our article. As you are concerned, there are several problems that need to be addressed. According to your nice suggestions, we have made corrections to our manuscript, the detailed corrections are listed below.

Question 1: The values given in table-6 should be rounded off to nearest whole number for example...387 to 390, 7.7 to 7.5, 19.3 to 19 or 20, and 801 to 800.

Answer: We have adopted your comments and rounded the values in Table 6 to the nearest whole number. The revised Table 6 is as follows:

Table 6. The mix ratio of each raw material for this test(kg/m³)

Serial number		Raw materials	Mix ratio
1	PM-200 isocyanate		390
2	ES305 polyether polyol		390
3	Kosmos-29 catalyst		7.5
4	HQEE chain extender		20
5	Silicate cement		800

 

Question 2: Give at least 5 keywords and arrange them in alphabetical order 

Answer: We supplemented the keywords from four to six and arrange them according in alphabetical order. These keywords were extracted from the manuscript and serve to summarize the central content of the paper. The modifications are as follows:

Keywords: damage mode; flexural properties; molecular structure; polyurethane cement; reaction mechanisms; temperature loading

Thank you again for all your hard work to help improve our manuscript!

 

Thank you and best regards.

Yours sincerely,

Hongshuai Gao

[email protected]

Author Response File: Author Response.docx