Preparation and Characterization of Insulating Panels from Recycled Polylaminate (Tetra Pak) Materials
Round 1
Reviewer 1 Report
The experiment is done and explain properly, the method and results are clear and well explained. I miss a comparation in terms of statistics and/or percentages with the other materials.
The results don't state or present the numerical evidence funded. You need to re-write the conclusions in terms of comparative and percentages, this material type x is equivalent to a x centimeters of polystyrene, in terms of fire rating, you need to states this material will be number of minutes that is fire proof (usually like EF30 or RF30) fire proof or fire resistant and the minutes, in terms of water, does it loose the property with humidity?
As I already stated the experiment is well done, the conclusions need to be re-write. You did a really good job
Author Response
Answers to Reviewer 1
Dear colleague,
first of all we thank you for the time you spent reviewing our work. We also thank you for the nice words spent in your comment.
We have tried to satisfy all your suggestions and we hope that in this form the work can be considered for its publication.
Below are the responses to your comments and in the text all changes are highlighted in yellow.
Greetings
The authors
Your Comments. The experiment is done and explain properly, the method and results are clear and well explained. I miss a comparation in terms of statistics and/or percentages with the other materials. The results don't state or present the numerical evidence funded. You need to re-write the conclusions in terms of comparative and percentages, this material type x is equivalent to a x centimeters of polystyrene, in terms of fire rating, you need to states this material will be number of minutes that is fire proof (usually like EF30 or RF30) fire proof or fire resistant and the minutes, in terms of water, does it loose the property with humidity?. As I already stated the experiment is well done, the conclusions need to be re-write. You did a really good job.
Answer 1)
In paragraph 3.3.1 has been supplemented with the following sentences: “Taking into consideration the ratio R, given by the temperature difference between the two chambers with respect to the thickness of the panel (R=DTchamber2-Tchamber1/panel thickness), it is possible to have a comparison parameter between the materials considered, all conditions being equal. The higher this parameter, the higher the insulating action of the panel. Taking as a reference 30 min of heating, in which the maximum temperature in chamber 2 is reached, the corresponding values of this ratio for the three materials analyzed are 17.3, 24.95 and 52.6 [°C/cm] respectively for the chipboard, polystyrene and polylaminate. The results obtained show, respect the same thickness, an R value of the polylaminate panel of about double that of polyethylene and about three times that of chipboard.”
Answer 2)
In paragraph 3.32 the following discussion has been integrated: “As can be seen from Figure 10a, after 300 seconds of flame exposure only the part subject to direct contact with the flame burned while the other remains in a normal state (Figure 10b). The material also proved to be very resistant to vertical flame propagation, in fact the trunk inside the brick container has not undergone any changes, indeed the panel inside was not even very hot to the touch.
The polylaminate panel therefore shows a high resistance to flame (RF) and after 300 sec of exposure it is only superficially altered.
This result is certainly satisfactory when compared with polystyrene or chipboard for which, as is known, they have a flame resistance (RF) of a few seconds [60,61].
In conclusion, it can be safely stated that the material has excellent flame resistance due to the aluminum sheets which during the exposure phase act as barriers preventing propagation by creating a sort of protective layer that slows the propagation of the flame. Furthermore, the flame resistance is also favored by the high compaction of the material which, unlike for example other materials such as chipboard, being instead very porous, favor the spread of flames”.
Answer 3)
In paragraph 3.3.3 we reported the water resistance of this panel prototype. Our aim was to verify the alterations that the sample undergoes in the presence of water rather than quantifying the amount of adsorbed water. In fact, at the end of the immersion time, the specimen was removed from the water and left to dry and subsequently the alterations suffered during the wet / dry cycle were verified.
In the paragraph there is the following comment: “As can be seen from the observation notes shown in Table 3, the polylaminate panel remains unchanged by immersing it in water for a time of one hour. This means that the infiltration of water, despite the presence cardboard layers, is not very fast. After one hour of immersion, the specimens begin to show small swellings at the corners that become increasingly greater as the hours of immersion increase, although despite this, they retain their shape after 12 hours (Fig. 11).”
However, we believe it is fair to explain all this better in the manuscript, so in paragraph 3.3.3 the following discussion has been inserted:
“The water resistance was conducted by immersing the samples completely in water at room temperatures for programmed time intervals. After each time interval, three specimens were removed from the water and left to dry for 72 hours at room temperature. Subsequently the samples were observed to verify the alterations suffered during the wet-dry cycle.”
Answer 4)
The conclusions have been revised and extensively integrated.
Reviewer 2 Report
The research is interesting as well as is interesting to know if you have already thought in which way the dimension of insulating panel can be increased... in which way tetra packs can be jointed each other for increasing the length and the high of panels that can be used (e.g.) as insulation for buildings, considering that thickness can be varied as you have explained in the paper. How can be solved the problem related to the water resistance of tetra pack edges? It, probably, will influence the connection of the tetrapack to each other... Can you add some considerations in this sense?
Author Response
Answers to reviewer 2
Dear colleague,
first of all we thank you for the time you spent reviewing our work. We have tried to satisfy all your suggestions and we hope that in this form the work can be considered for its publication.
Below are the responses to your comments and in the text all changes are highlighted in yellow.
Greetings
The authors
Your comments. The research is interesting as well as is interesting to know if you have already thought in which way the dimension of insulating panel can be increased... in which way tetra packs can be jointed each other for increasing the length and the high of panels that can be used (e.g.) as insulation for buildings, considering that thickness can be varied as you have explained in the paper. How can be solved the problem related to the water resistance of tetra pack edges? It, probably, will influence the connection of the tetrapack to each other... Can you add some considerations in this sense?
Answer) The following discussion was incorporated into the conclusions: “Since the polylaminate sheets obtained from recycled packing, generally could have a maximum size of 20x30 cm, the production of a panel of larger dimensions, that is with dimensions typical of an insulating panel used for construction, presupposes two important aspects to take into consideration: the overlapping of the sheets and the areas of surface discontinuity between the sheets.
The first aspect, that is the overlapping of the sheets, should be carried out simply by overlapping the different sheets one on top of the other in a staggered way. All this would not lead to particular variations, although industrial presses of adequate size would be needed and which in our case it was not possible to have them available in the laboratory.
The other aspect is the areas of discontinuity between the juxtaposition of one sheet and another, which would be generated on the front and rear surfaces and which could represent areas of weakness respect to any infiltration of water. All this could be easily overcome by using any waterproofing material that would prevent any infiltration of water in the areas of discontinuity, that is, both on the surfaces and on the edges. A waterproofer, for example, could be a common resin. Another option could be the application of a superficial thin aluminum or PVC film over the entire panel which would also increase the appearance of the panel from an aesthetic point of view. However, it is necessary to emphasize that the waterproofing of the panel is not always essential, bearing in mind that from the results obtained, the panels show an acceptable resistance to water infiltration. Furthermore, for an assumed use as insulating panels, their most probable location should be in the cavities between walls, where there is hardly any contact with water. “
Reviewer 3 Report
The study presents very interesting results on using Tetra Pak waste material to build insulating panels. This seems like a novel and useful research. The experimental work and discussion on what is obtained is finely and clearly explained. However, there are many serious remarks on this work, as follows.
- The combinations of the number of layers, temperature and drying time are varied satisfactorily, but not all of them are presented in Table 1.
- There are more then 50 references in the list, but none is mentioned in the experimental nor discussion parts. All of the references are grouped in the Introduction section.
- How were the production of the specimens selected? Based on previous research or a literature data?
- The obtained results are not compared to other previous studies on any kind panel, and there are a lot of research on this subject. The novelty of this study over the previous ones should be emphasized in the Abstract and Introduction sections.
- The test aimed to check the thermal conductivity does not seem to be efficiently conducted, bearing in mind it is done in a wooden box.
- More experimental work is needed so this study can be more scientifically oriented. At this moment it is more like a technical paper. What was the thickens of the initial boards, and what after the thermal treatments? What were water absorption results? How high was the bending strength? What was the microstructure like? Which was the chemical reaction between the layers that bonded them? What about acoustical insulation of these boards? Of course, there is also a great question on how the boards will behave when scaled up to a larger specimen.
- To sum up, the work needs more scientific data and a better discussion.
Author Response
Answers to reviewer 3
Dear colleague,
first of all we thank you for the time you spent reviewing our work.
We have tried to satisfy all your suggestions and we hope that in this form the work can be considered for its publication.
Below are the responses to your comments and in the text all changes are highlighted in yellow.
Greetings
The authors
Your comment 1.The combinations of the number of layers, temperature and drying time are varied satisfactorily, but not all of them are presented in Table 1.
Answer 1) In table 1 we have reported how each single parameter (such as time, temperature, pressure, number of sheets) has been made to vary and not the different combinations between them. However for better clarity we have inserted the following comment in paragraph 2.2: "The following Table 1 shows the different values of each parameters (such as time, temperature, pressure, number of sheets) that were used to find the best experimental conditions for the preparation of the specimens.
Your comment 2. There are more then 50 references in the list, but none is mentioned in the experimental nor discussion parts. All of the references are grouped in the Introduction section.
Answer 2). This new part has been integrated in the introduction and other references have been added: “One of the most active sectors in researching new materials is certainly that of construction. In particular, in the construction sector of great importance is the construction of panels that are used in different ways such as for interspaces, in thermal and acoustic insulation, etc.
Many natural materials have been extensively investigated for the production of insulating panels such as: pine bark, bamboo fibers, hemp etc. The data reported in the literature confirm the possibility of using natural materials, with satisfactory thermal insulation characteristics and above all the advantage of obtaining products mainly of natural origin [44-47].
The literature also reports numerous studies on the use of waste materials for the preparation of panels with the advantage of contributing to environmental sustainability. [48-51].”
In paragraph 3.3.2 the following discussion has been integrated: “As can be seen from Figure 10a, after 300 seconds of flame exposure only the part subject to direct contact with the flame burned while the other remains in a normal state (Figure 10b). The material also proved to be very resistant to vertical flame propagation, in fact the trunk inside the brick container has not undergone any changes, indeed the panel inside was not even very hot to the touch.
The polylaminate panel therefore shows a high resistance to flame (RF) and after 300 sec of exposure it is only superficially altered. This result is certainly satisfactory when compared with polystyrene or chipboard for which, as is known, they have a flame resistance (RF) of a few seconds [60,61].
In conclusion, it can be safely stated that the material has excellent flame resistance due to the aluminum sheets which during the exposure phase act as barriers preventing propagation by creating a sort of protective layer that slows the propagation of the flame. Furthermore, the flame resistance is also favored by the high compaction of the material which, unlike for example other materials such as chipboard, being instead very porous, favor the spread of flames”.
Your comment 3. How were the production of the specimens selected? Based on previous research or a literature data?
Answer3) There is very little research on recycled Tetra pack in the literature. Therefore, we did not refer to other works. Our research initially made use of our preliminary investigations which were only partially reported in the manuscript, because not all of them were significant. Paragraph 3.1 shows the most significant preliminary texts.
Your comment 4.The obtained results are not compared to other previous studies on any kind panel, and there are a lot of research on this subject. The novelty of this study over the previous ones should be emphasized in the Abstract and Introduction sections.
Answer 4).
In Abstract was added following sentence: “The advantage of the thermal method is that it does not use chemical or other binders and also uses only and exclusively sheets of recycled polylaminate”.
In the introduction this part has been added and new references inserted: “One of the most active sectors in researching new materials is certainly that of construction. In particular, in the construction sector of great importance is the construction of panels that are used in different ways such as for interspaces, in thermal and acoustic insulation, etc. Many natural materials have been extensively investigated for the production of insulating panels such as: pine bark, bamboo fibers, hemp etc. The data reported in the literature confirm the possibility of using natural materials, with satisfactory thermal insulation characteristics and above all the advantage of obtaining products mainly of natural origin [44-47]. The literature also reports numerous studies on the use of waste materials for the preparation of panels with the advantage of contributing to environmental sustainability. [48-51]”;
“The method is mainly proposed to use only recycled material and without the addition of chemical or other binders.”
In paragraph 3.3.2 this part has been added:
“The material also proved to be very resistant to vertical flame propagation, in fact the trunk inside the brick container has not undergone any changes, indeed the panel inside was not even very hot to the touch.
The polylaminate panel therefore shows a high resistance to flame (RF) and after 300 sec of exposure it is only superficially altered.
This result is certainly satisfactory when compared with polystyrene or chipboard which, as is known, they have a flame resistance (RF) of a few seconds [60,61].
In conclusion, it can be safely stated that the material has excellent flame resistance due to the aluminum sheets which during the exposure phase act as barriers preventing propagation by creating a sort of protective layer that slows the propagation of the flame. Furthermore, the flame resistance is also favored by the high compaction of the material which, unlike for example other materials such as chipboard, being instead very porous, favor the spread of flames.”
Your comment 5. The test aimed to check the thermal conductivity does not seem to be efficiently conducted, bearing in mind it is done in a wooden box.
Answer 5). In reality, the two chambers are made of wood externally but internally they are covered with thermo-reflective panels that guarantee efficient thermal insulation. For a better description in the text, the following sentence has been inserted in paragraph 3.3.1: “To better isolate the internal environment from the external one, the two chambers were internally lined with heat-reflecting panels”.
Your comment 6. More experimental work is needed so this study can be more scientifically oriented. At this moment it is more like a technical paper. What was the thickens of the initial boards, and what after the thermal treatments?
Answer 6). In paragraph 3.1 the following sentence is already reported: "A decrease in thickness, after heat treatment, of about 13.5%, due to good compaction and also a decrease in weight of about 54.76% due to the loss of moisture present in the sheets before treatment, was highlighted". It is true that this comment is included only in the discussion of the preliminary studies although this trend has always been found in the specimens that presented an optimal degree of compaction”. However, for a better understanding, the following sentence has also been inserted in paragraph 3.2:"All the specimens that showed a good compaction (green dot), have undergone a decrease, compared to the specimen before the heat treatment, of the thickness of about 13/14%, and a weight loss of about 55/60%.
Your comment 7. What were water absorption results?
Answer 7). In paragraph 3.3.3 we reported the water resistance of this panel prototype. Our aim was to verify the alterations that the sample undergoes in the presence of water rather than quantifying the amount of adsorbed water. In fact, at the end of the immersion time, the specimen was removed from the water and left to dry and subsequently the alterations suffered during the wet / dry cycle were verified.
However, we believe it is fair to explain all this better in the manuscript, so in paragraph 3.3.3 the following discussion has been inserted: “The water resistance was conducted by immersing the samples completely in water at room temperatures for programmed time intervals. After each time interval, three specimens were removed from the water and left to dry for 72 hours at room temperature. Subsequently the samples were observed to verify the alterations suffered during the wet-dry cycle.”
Your comment 8. How high was the bending strength? What was the microstructure like?
Answer 8). Rightly in future studies, it will be necessary to investigate further characteristics. Unfortunately, at the moment we do not have the possibility to carry out these further characterizations in our laboratory. Since our main purpose was to test a method for the preparation of an insulating panel from recycled material, we therefore mainly tested the thermal conductivity as well as the effectiveness of the thermal method. However, we hope in the future to deepen further characteristics of the material, as you rightly suggested.
Your comment 9. Which was the chemical reaction between the layers that bonded them? What about acoustical insulation of these boards?
Answer 9). In the assembly of the recycled polylaminate sheets, no chemical reagents were used but only heat and pressure were used. The sheets bonded, not the action of chemical reactions, but only following the softening and cooling of the external Polyethylene films present on the polylaminate sheets, as partially explained in paragraph 3.1. Following your just observation we found it appropriate to explain further in the manuscript and inserting the following sentence in the conclusions: “The thermal method experimented in this research proved to be feasible for the preparation of insulating panels, from polylaminate sheets obtained from recycled packing. The method does not involve the use of chemical additives but takes advantage of the presence of polyethylene films present on the surface of the recycled polylaminate sheets. The latter during the treatment phases, following the high temperatures, soften and subsequently cool, allowing the adhesion of the sheets which is also favored by the combination with pressure.”
Your comment 10. Of course, there is also a great question on how the boards will behave when scaled up to a larger specimen.
Answer 10). The following discussion was incorporated into the conclusions. “Since the polylaminate sheets obtained from recycled packing, generally could have a maximum size of 20x30 cm, the production of a panel of larger dimensions, that is with dimensions typical of an insulating panel used for construction, presupposes two important aspects to take into consideration: the overlapping of the sheets and the areas of surface discontinuity between the sheets. The first aspect, that is the overlapping of the sheets, should be carried out simply by overlapping the different sheets one on top of the other in a staggered way. All this would not lead to particular variations, although industrial presses of adequate size would be needed and which in our case it was not possible to have them available in the laboratory.The other aspect is the areas of discontinuity between the juxtaposition of one sheet and another, which would be generated on the front and rear surfaces and which could represent areas of weakness respect to any infiltration of water. All this could be easily overcome by using any waterproofing material that would prevent any infiltration of water in the areas of discontinuity, that is, both on the surfaces and on the edges. A waterproofer, for example, could be a common resin. Another option could be the application of a superficial thin aluminum or PVC film over the entire panel which would also increase the appearance of the panel from an aesthetic point of view. However, it is necessary to emphasize that the waterproofing of the panel is not always essential, bearing in mind that from the results obtained, the panels show an acceptable resistance to water infiltration. Furthermore, for an assumed use as insulating panels, their most probable location should be in the cavities between walls, where there is hardly any contact with water.”
Round 2
Reviewer 3 Report
The authors made a great effort to improve the text and clarity. Now the manuscript is ready to be published.
