Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution
, Lina Ji 1,*,†, Delin Sun 2,*, Zhangheng Wang 2, Hui Ge 1, Man Xu 1 and Minggong Yu 2
Round 1
Reviewer 1 Report
To my regret, the article in this version leaves a satisfactory impression.
A few remarks.
1. There is no acceptable description of how the samples were made, the properties of which are shown in Figures 2-4. It would be nice if there was information about how they differ, while it is clear that some were impregnated with a softening solution, while others were not. But it would be clear if the regiment would be duplicated both in the experimental part and in the captions to the figures.
2. The wood impregnation is not clear, it is better than the compositions currently used or described in other works. Lack of literature discussion.
3. There are inaccuracies and misprints in the text of the article, 3.1.1. Subsubsection is such a name? And the captions on the drawings must be written in English.
Author Response
Point 1: There is no acceptable description of how the samples were made, the properties of which are shown in Figures 2-4. It would be nice if there was information about how they differ, while it is clear that some were impregnated with a softening solution, while others were not. But it would be clear if the regiment would be duplicated both in the experimental part and in the captions to the figures.
Response 1:
According to the Reviewer’s comments, we have added a description of the samples that have not been impregnated with softening solution in “materials and methods”. The specific content: “In order to deeply study the effect of softening solution vacuum impregnation on the bending of teakwood, the softening and bending properties of impregnated and unimpregnated wood will be compared and analyzed in the experiment. Softening bending of unimpregnated wood means that the specimens are not impregnated with softening solution vacuum impregnation, but only by steaming, including two process parameters: softening temperature and time.”
Point 2: The wood impregnation is not clear, it is better than the compositions currently used or described in other works. Lack of literature discussion.
Response 2:
According to the Reviewer’s comments, we added relevant references in the Introduction. The content is: “Wang et al. [8] used ammonia solution to analyze the softening process of teakwood, the bending coefficient is 1/21, and its bending performance is obviously better than hydrothermal treatment. Shen et al. [9] studied the softening process of ammonia solution and steam synergistic treatment of teakwood by response surface methodology and analyzed the effects of alkali concentration, treatment temperature, and treatment time on the softening properties of wood, and the results showed that vacuum impregnation of ammonia solution was conducive to the softening bending of teakwood, and the bending coefficient could reach 1/12.2, and mechanical properties such as maximum loading, bending strength and elasticity modulus of specimens were improved to a certain extent after drying and shaping. Yao et al. [10] used the synergistic treatment method of triethanolamine and superheated steam for the softening of teakwood, the bending properties of the teakwood were further improved, and the macroscopic and micromechanical properties of the specimens were analyzed, but the softening process, softening mechanism and other aspects are not further studied, especially the change relationship of the bending mechanics didn’t have relevant research.”
Point 3: There are inaccuracies and misprints in the text of the article, 3.1.1. Subsubsection is such a name? And the captions on the drawings must be written in English.
Response 3:
I am really sorry for the mistakes due to our negligence. We have corrected them in the manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The article describes a method of softening teakwood by vacuum impregnation with triethanolamine using saturated steam as a medium. Chemical analysis including FTIR, NMR, XPS and SEM was used to characterize the teak softening mechanism. The subject of the research is interesting; however, the manuscript has some shortcomings that require correction or clarification.
1. The Abstract should include detailed information on the method of wood treatment.
2. The Introduction omitted information about the article describing the study of softening and bending teakwood impregnated with triethanolamine and superheated steam as a medium (Linghua Yao, Delin Sun, Zhangheng Wang & Minggong Yu (2023) Triethanolamine impregnation/steam synergistic softening of teakwood to improve bending properties and its mechanism, Wood Material Science & Engineering, 18:2, 618-629, DOI: 10.1080/17480272.2022.2057815). Authors should clearly indicate what is new in this work and what distinguishes it from the published and referenced article above.
3. Lines 39-42 and 45-51: these sentences are incomprehensible and needs to be reworded.
4. Lines 73-75: the information contained in this sentence describes the methods used in the study and should not be included in the Introduction section.
5. Line 93-94: why exactly such mass ratios of reactants were used in the research?
6. The section 2.1.2. (Softening and bending process) should be written in the past tense.
7. In the methodology, it should be added that the influence of several factors (temperature, time and different softening solution concentrations) on bending properties of teakwood was tested.
8. Line 179: subsection name is missing.
9. Figures 2 and 3: the legend and other elements shown in the charts should be explained in English.
10. Conclusion should be edited and contain only conclusions, not a description of the tests that were performed during the research.
Author Response
Point 1: The Abstract should include detailed information on the method of wood treatment.
Response 1:
According to the suggestions of the reviewers, we have added more detailed information on wood treatment methods in the abstract. The specific content: “To study the softening bending properties and mechanism of teakwood, and it was extractively pretreated by using superheated steam, the triethanolamine compound was used as a softening solution, which was infiltrated into the wood by vacuum impregnation and synergistically softened through saturated steam to improve the bending properties of teakwood.”
Point 2: The Introduction omitted information about the article describing the study of softening and bending teakwood impregnated with triethanolamine and superheated steam as a medium (Linghua Yao, Delin Sun, Zhangheng Wang & Minggong Yu (2023) Triethanolamine impregnation/steam synergistic softening of teakwood to improve bending properties and its mechanism, Wood Material Science & Engineering, 18:2, 618-629, DOI: 10.1080/17480272.2022.2057815). Authors should clearly indicate what is new in this work and what distinguishes it from the published and referenced article above.
Response 2:
(1) According to the suggestions of the reviewers, we have added the references, and discussed them in the introduction. The specific content: “Yao et al. used the synergistic treatment method of triethanolamine and superheated steam for the softening of teakwood, the bending properties of the teakwood were further improved, and the macroscopic and micromechanical properties of the specimens were analyzed, but the softening process, softening mechanism and other aspects are not further studied, especially the change relationship of the bending mechanics didn’t have relevant research.”
(2) The experimental methods are different, this article is synergistic softening by saturated steam, and the published article is synergistic softening by superheated steam; the contents of the research are different, the main contents of this article: process optimization, softening mechanism and the construction of bifold model of bending mechanics, while the main contents of the published article: the one-factor analysis of the softening solution, macroscopic and microscopic mechanical properties, and the softening mechanism, and so on.
Point 3: Lines 39-42 and 45-51: these sentences are incomprehensible and needs to be reworded.
Response 3:
(1) According to the suggestions of the reviewers, we have revised the expressions in line 39-42. The specific content:“Recently, scholars have used chemical-physical synergistic softening methods to improve the softening properties and bending quality of wood, to solve the problems of insufficient softening and softening collapse that exist in a single softening process.”
(2) Lines 45-51: Since the reference only studied the softening properties and mechanisms of poplar wood, and did not studied the bending properties, so this sentence was deleted.
Point 4: Lines 73-75: the information contained in this sentence describes the methods used in the study and should not be included in the Introduction section.
Response 4:
According to the suggestions of the reviewers, we have deleted lines 73-75.
Point 5: Line 93-94: why exactly such mass ratios of reactants were used in the research?
Response 5:
In the experiment, triethanolamine was the main softening solution, NaCl was the penetrating agent and SDBS was surfactant. In the preliminary experiments, it was found that different concentrations of softening solution had different effects on the bending properties of teakwood, NaCl and SDBS were added in a certain ratio was conducive for the softening solution to penetrate into the interior of the wood under the conditions of vacuum impregnation and thus enhance the softening effect. In the main text, the expression was modified: “The mass ratio of distilled water to TEA was 100:5, 100:10, 100:15, 100:20, NaCl: SDBS: TEA= 1:1:7.”
Point 6: The section 2.1.2. (Softening and bending process) should be written in the past tense.
Response 6:
We have revised the sentence tenses point by point. The specific content: “The teakwood specimen softening and bending process mainly consisted of four steps: pretreatment, vacuum impregnation with softening solution, softening and bending, drying and shaping. Firstly, pretreatment, the teakwood specimens were put into superheated steam equipment at 120 °C for 60 min for extractive pretreatment of the specimens. Next was the softening solution vacuum impregnation, the specimen would be put into the impregnation test tank, extract the vacuum, when the vacuum degree reached -0.08 MPa, for 60 min, followed by the inhalation of the softening solution, and then the 0.5 ~ 1 MPa pressure, pressure impregnation for 120 min, then unpressurized. Repeated it 3 to 5 times, so that the softening solution was fully penetrated the teakwood. The second was softening and bending, the impregnated teakwood specimens were put into the softening tank, at 100 ~ 140 °C saturated steam for heating and softening for 90 ~ 210 min. They would be placed in the bending machine for bending under pressure at a constant speed after the specimens were softened. In the process, temperature, time, and concentration of softening solution were selected as the main influencing factors for experiments. Finally, drying and shaping, successful bending specimen were fixed by using an F-type fixture, and then were put into the superheated steam equipment to dry and shape at 130 °C for 120 min, with heating rate at 60 °C/h.”
Based on the above process, high-temperature steam pretreatment enabled the pit membrane of the teakwood to be partially penetrated and the inclusions in the conduit to be partially expelled, to improve its permeability [16]. The teakwood was impregnated by using the method of “negative pressure - positive pressure” to deeply penetrate the softening solution into teakwood. Then, under saturated steam conditions, the reaction between the softening solution and the chemical constituents of the teakwood, not only penetrated the non-crystalline zone but also maked the crystalline zone of cellulose wetting and swelling, thus improving the softening effect and plastic deformation capacity [17]. The teakwood bending components were deformation fixed by superheated steam to reduce their deformation recovery capacity and improved dimensional stability in the process of drying and shaping. The softening principle and bending process were shown in Figure 1.
Point 7: In the methodology, it should be added that the influence of several factors (temperature, time and different softening solution concentrations) on bending properties of teakwood was tested.
Response 7:
(1) According to the reviewer’s suggestion, we added the description of the experimental method in 2.2.2. The specific content:“In the process, temperature, time, and concentration of softening solution were selected as the main influencing factors for softening bending experiments.”
(2) In 3.1.2, the three-factor, three-level process optimization with Response Surface was used, as shown in Table 1.
Point 8: Line 179: subsection name is missing.
Response 8:
We’ve added the subsection name: Single-factor testing results.
Point 9: Figures 2 and 3: the legend and other elements shown in the charts should be explained in English.
Response 9:
We’ve corrected Figures 1 and 2.
Point 10: Conclusion should be edited and contain only conclusions, not a description of the tests that were performed during the research.
Response 10:
According to the reviewer’s suggestion, we have revised the conclusion. The specific content: “In summary, this study showed that the teakwood softening process can obtain the best bending properties after Response Surface Optimization. When saturated steam was used to synergistically treat the impregnated material with triethanolamine compounding solution, the functional groups in the softening solution chemically bonded with the chemical constituents in teakwood, forming C-NH2 and C-N bonds, and the reactive substances were expressed, which improved the softening properties of teakwood. Compared with the traditional hydrothermal softening method, the specimens prepared by vacuum impregnation with triethanolamine compound had excellent bending properties. What’s more, based on the mechanical changes of the softening and bending process of teakwood, a bifold constitutive model with a high degree of fitting was constructed, which proved the applicability of the model. Therefore, the preparation of teakwood bending components by using triethanolamine compounding solution provides an economical and environmentally friendly method for the softening and modification of hardwood materials, and has a good application prospect in the field of bending wood product processing.”
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
I have no further comments, except for minor correction as below.
Lines 54-60: This sentence is incomprehensible and should be reworded.
