Round 1

Reviewer 1 Report

The authors focus on interesting problematics, namely the change in adhesion, finishing and "durability" of wood after heat treatment in two Taiwan's native wood species. Heat treatment as an ecological method has been widely used in recent times, in particular to improve the dimensional stability and durability of wood. In a way, the article is supposed to contribute to raising awareness of the possibilities of wood use in Taiwan, and to reduce its more than 99% export without any final domestic use.

Although these are interesting results, I have a considerable amount of less or more important comments to research.

Interesting could be the results of selecting the appropriate treatment temperature, the rate of temperature growth, duration of peak phase of treatment, and material thickness (see introduction, line 76-82). It was an assessment based on dimensional stability, hardness and static bending strength of woods. Are these data a part of any other article? If not, then why were not used in this one? In any case, I consider the temperature of the treatment to be suitable, for hardwood apparently also the maximum (at a higher temperature there is a large decrease in mechanical characteristics). In any case, it is more appropriate for assessment to apply instead of static MOR rather impact bending strength.

I see a lack of more information on cutting of the test material and especially on the number of samples in individual test series, or how their incorporation into them occurred. Wood is such a variable material that in the case of a low number of samples or incorrect incorporation into the test series, the result can be distorted just by its variability. Moreover, it is about anisotropic and inhomogeneous material as it is known, and thus, for example, fiber deflection may be substantial.

The samples should always be conditioned in given surroundings parameters until EMC stabilization, a period of 1 week may not be always clearly sufficient.

I see a lack of information about wood parameters, i.e. its density, which is a basic physical quantity that as I think would definitely be measured. In addition, the moisture content of the wood should be determined before the individual experiments (reference approx. 12.0%, heat-treated wood approx. ...).

Only two standards are mentioned in the methodology, but these are not even mentioned in the literature. Addition is required, others also.

From my point of view, the measurement of wettability (contact angle) before and after the heat treatment of wood could be included, with regard to this type of research, i.e. the application of wood adhesives and coatings.

Interpretation of the results in the form of tables can take a lot of effort from the perspective of understanding the results. At least the occasional inclusion of the graphic appearance of the most important results would be much more effective and, above all, more illustrative.

For wood, the basic file size of 30 samples (for each series) is considered, which can be applied for small standard samples. If you did not have a sufficient number of samples in the individual test series, then the predictive power of this research is indeed only preliminary. With that, therefore, also relates statistical significance of the results obtained, which is necessary to verify, for example through a quantile of Student distribution and related measurement variability (COV).

From the point of view of statistical evaluation, it would be appropriate to include also statistical analysis ANOVA, i.e. comparison of results for a given quantity before and after heat treatment at the selected level of significance.

I would make corrections or additions, in the context of the above written, even if it is quite clear that, for example, the number of samples will not change. However, it is advisable at least to supplement the statistical significance of individual tests for the selected measurement accuracy at a given level of significance, and to complete the sampling and cutting information as well as all relevant standards (norms). Conclusions should also be supplemented by some concrete values or at least % decrease or increase of the given value (quantity). I consider the discussion with respect to the interpretation of the results as quite correct and logical. However, I would also apply another form of displaying the results in the form of graphs (even as a part of ANOVA).

Author Response

The reply is provided in the Word  file.

Author Response File: Author Response.docx

Reviewer 2 Report

Review of article (manuscript) for the journal FORESTS   

Manuscript Number: forests-537854

Manuscript submitted: 21 June 2019 (12 p.)

Title of the manuscript (Original Article):

Adhesion, finishing and decay resistance performance of heat-treated wood

Authors: Chang, C.W., Kuu, W.L., Lu, K.T.

The manuscript presents experimental knowledge about surface characteristics and rot-resistance of two heat-treated wood species important in Taiwan - Cryptomeria japonica and Acacia confusa. It gives some new views on thermal modification of wood. However, the majority of results is explained only hypothetically without experimental analyses made in the presented article (e.g. hydrophobic extracts and VOC derived from hemicelluloses moved to wood surfaces, which obtained a lower wettability and lower pH values; increasing of cellulose crystallinity; …).

Comments:

·       Abstract: It is too long, but without presentation of wood properties improving after thermal modification in percentage, or on the basis of statistical analyses, e.g. by Duncan test.    

·       Introduction, page 1, line 44: The chemical modification methods (esterification and etherification) are not the traditional treatments of wood unlike of its treatments with CCA, ACQ or other preservatives.

·       Introduction, page 2, lines 77 – 78: From the mentioned technological parameters (T = 130, 160, 190, 220, 250 and 280 °C; t = 1, 2, 3 h; thickness – 30, 50, 70 mm; v = 10, 20, 30 °C/h) were in the experiment applied only selected ones (190 °C; 1 and 2 h; 50 mm; 10 °C/h), and therefore here should be given an information that with the other technological parameters were already performed other experiments with preparing other articles.  

·       Figure 2, dimension of the sample, page 3: In the text (line 118) is 35 mm x 25 mm x 20 mm, but in the figure 30 mm x 25 mm x 20 mm.

·       Point 2.3, page 4, lines 148-150: CIELab colour system – it for yellowness difference uses Db symbol instead of DYI.

·       Point 3.2, page 6, line 207: For NC lacquer the height of striking is 10 cm, but in Table 2 is other value 5 cm.

·       Figures 5 and 6: These figures are not important in the article, as the colour of untreated and heat-treated woods can be seen as well as from Figures 3, 4 and 7, at which their finishing with lacquers have only specific effects on their colour and total appearance.

·       Tables 4 and 5: By the CIELab colour system the value of DE should be higher than the values of DL or DYI (Db).

·       Conclusions, page 9, line 312: “… showed no significant differences …”. However, in the article were not performed statistical analyses of significance, e.g. the Duncan tests.

·       References: For comparison of results in point 3.3, the colour changes and weight losses of woods (e.g. several tropical species) due to decay processes were presented in several works (e.g. Forests 2019, 10(322): 14 pp.  ISSN 1999-4907, DOI: 10.3390/f10040322).    

 

Finally, I can recommend the article for publication in your scientific journal after major revisions.

Author Response

The reply is provided in the Word file.  

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Review of article (manuscript) for the journal FORESTS   

Manuscript Number: forests-537854

Manuscript after revision submitted: 08 July 2019 (12 p.)

Title of the manuscript (Original Article):

Adhesion, finishing and decay resistance performance of heat-treated wood

 

Authors:

Chang, C.W., Kuu, W.L., Lu, K.T.

___________________________________________________________

The revised manuscript is convenient for publication in the scientific journal Forests.

08 July 2019                                                                               Reviewer