Surface Characteristics and Acoustical Properties of Bamboo Particle Board Coated with Polyurethane Varnish

REVIEWER 1

1.     

Lines 108 and 109: The experimental errors of the dimensions of the particles are very surprising. Which kind of experimental device did you use?

Thank you for your comments. This study followed the previous study by Karlinasari et al. (2012, 2021). The coarse particle size followed the sawdust size, while fine particles was smaller. Those particle sizes are mentioned in Maloney’s book (1993) Ch. 6. Therefore, we believe the dimensions mentioned on lines 108 and 109 are reasonable for particle board. The way on how to manufacture the particle sizes has been explained in the text “Two papers by Karlinasari et al. [5, 12] outlined the technique for obtaining fine and coarse particles, as well as the manufacturing of particle board panels. “

We used a disk-flaker for making coarse particles size, and a hammer mill and screened on a 10‐mesh sieve for making fine particles as mentioned in reference.

2.     

Please to use scientific notation. No use cm3

Thank you, we have revised the scientific symbol per your suggestion.

3.     

Sections 2.1 and 2.2. Please to include pictures of the samples preparation and coating application

Thank you.

For Section 2.1: we think it is clear to manufacture the particle board as mentioned in line 115 to 117. That line explains the procedure standard to make particle board as in the references.

For Section 2.2: Thank you, we have inserted the picture (figure 1 line 147)

4.     

Figure 1. Changes Sampel for Sample

Thank you,
we have revised the word of sample.

5.     

Section 2.3. Please to include info of the signal processing. Data regarding sampling frequency, etc. And even some example a signals.

Thank you, we have revised and added some information (including added sub-Figure) to explain the acoustical properties measurement.

6.     

The samples nomenclature is quite difficult to understand. Specially, you have to change this nomenclature for a fast and immediate understanding on the figures with results.

Thank you, we tried to make the nomenclature as simple as we can since we felt that the description to explain the treatments in detail is too long. We do hope the nomenclature with a letter abbreviation is easy to understand. So we continue to use the submitted nomenclature.

For example,

F = fine particles, C= coarse particle, d= board density. While nominals such as 0.4 and 0.6 are to explain the board density.

7.     

Figure 2. Please to include the errors bars

Thank you, we have revised Figure 2 (in revision version become Figure 3)

8.     

Sometimes you use, and sometimes you use . for decimals. Please, unify your style.

Thank you, we have revised all of them.

REVIEWER 2

1.     

Write a short description about PU, and its coating/lacquer in Introduction.

Thank you, we have added the short explanation of PU.

2.     

Please correct it ''diphenylmethane diisocyanate isocya- 111
nate resin (MDI resin)''.

Thank you, we have revised it.

3.     

Please clearly explain the mixing of particle in PU, in experimental section. The way you described is not clear.

Thank you for your comment. We did not mix the particle in PU. We carried out spraying method for coating PU varnish on the particle board. To explain this way, we have added explanations in the text (line 132).

4.     

You used a commercial PU, mention the solvent. 

Based on specification from the PU producer, it uses thinner polyurethane MD. The producer does not mention the solvent, but using a term of thinner as PU coating composition.

5.     

 You didn't mention about curing, please mention the curing time and temperature. How you confirmed the coating was free from solvent after drying/curing?

Thank you, we have mentioned about curing in the text (line 139).

To confirm the coating treatment was free from coating solvent, the samples were conditioned for three days. We explain in line 141-142. The producer recommendation after one day the coating will dry

6.     

Clearly mention about wet and dry coating thickness.

Thank you, it was “dry coating thickness”. We have added the explanation in the text (line 141-142). We measured after 3 days of conditioning, after finishing application..

7.     

Check the PU solid content and mention it.

Thank you, the solid content of PU varnish was 40%. We have added the information in the text (line 122).

8.     

Why the contact angle decreased? please shortly explain. 

Thank you, we have mentioned the explanation such as in line … and … For example:

·      “Aydin [37] and Gindl et al. [38] mentioned that this was related to interfering coating penetration or the anchoring ability of the coating to the wood substrate because of surface inactivation.” (line 227);

·      “In terms of comparison between particle sizes, the result found the coarser of the surface roughness (Figure 5), the lower of the CA (Figure 6), which means better hydrophilicity.” (line 268-269);

·      “The lower CA values refer to the easiness of a liquid to enter and/or spread to the surface material” (line 292)

REVIEWER 3

1.     

line 122, 142 (table 1), 218, 294 and more - please, use the superscripts when say m2 or m3

Thank you for your suggestions. We have revised the scientific symbols.

2.     

line 132 and 133 - please, recalculate the given pressure to MPa

Thank you, we have calculated and revised it in the text (line …).

12 Psi = 0.0827 MPa

20 psi = 0.1378 MPa

3.     

line 142 (table 1): plase use dot instead of comma as decimal; since in every board type you used 3 panels (repetitions), I suggest to say it above the table in text, and remove the "Number" column form table 1

Thank you, we have revised them per your suggestions.

4.     

line 147 - I'm afraid there is an error or missing letter in the information about stylus radius (in my copy is 5 m)

Thank you. Yes, it should be 5 m. We have revised it in the text.

5.     

 line 149 - you said roughness tracking length was 0.25 mm; don't you think that was too short, in reference to your bamboo particles dimensions? I'm afraid you can measure the roughness of particle surface, without measuring the profile between adjacent particles, where the roughness can be totally different

Thank you, we apologize for our mistakes. It should be 15 mm. We have revised the text (line 157). For diamond tip stylus in a radius used was 5 m; and tracing length in surface roughness testing was 15 mm. The same method was used in Karlinasari et al. (2021).

6.     

line 152 - you used water to measure the contact angle; in my opinion it is hard to comment the surface phenomenas between PU varnish (totally different than water nor waterborne varnishes) and bamboo panel referring it to contact angle measured with water; please provide the justification that your comments to results achieved for two totally different liquids (water and PU varnish) on bamboo panel surfaces are reasonable

Thank you. In our study, we observed the water penetration on the surface that was coated by PU varnish. We evaluated the wettability of the sample that have been coated. It was continued by evaluating the physical properties of thickness swelling (TS) and water absorption (WA).

As for the mentioned explanation, we have added statement in the text (line 293-295): “In addition to decorative and excellent surface, the purposes of particleboard coating are to suppress the absorption of water and humidity, in term of dimensional stability, to extent its service life [14, 3]”

7.     

line 155 - there is an information that you measured thickness swelling, but in line 159 you said that you measured both, weight and thickness of the samples, what can indicate that you calculated also water absorption, but there is no results of water absorption; please explain why you measured weight of the samples? What was the dimensions of samples to thickness swelling measurement?

Thank you. We did measure the water absorption of the samples. In the revised manuscript, we have put the result and discussion of water absorption (line 296; Figure 8 and Table 5). Regarding the samples, we used TS and WA samples from sound absorption samples. The testing was conducted after acoustical measurement.

8.     

figure 1 - please use "sample" instead of "sampel"

Thank you, we have revised it.

9.     

line 187 - I think it should be said particle "size" instead of particle "shape", since you did not characterize the shape of the particles

Thank you, we have revised it.

10.  

figure 2 - please use dot instead of comma in decimals

Thank you, we have revised it.

11.  

figure 3 - please provide the scale bars on the pictures

Thank you, we have added it.

12.  

line 271-272 - concerning your comments to thickness swelling results: since the samples were fully immersed in water through 24h, and wide surfaces of the panels have been covered by PU varnish, don't you think the influence of varnish presence was hard to measure, since the water can penetrate the sample also through side surfaces (which were not protected agains water penetration)? In my opinion to evaluate the varnish layer on particleboard protection efficiency against water, a Cobb ring test would be more valuable - can you provide your opinion on this case?

Thank you for your comment. For that reason, we have added the result of water absorption.  The water absorption relies on the ability of the sample to absorb the water. We also have added explanation in the text mentioning that physical properties of TS and WA were carried out referring to the coating purposes to suppress the absorption of water and humidity (line 293-295).

We did not conduct Cobb ring but directed fully immersion in the water. After a specific soaking time, the samples were taken out from water and dried immediately using a clean dry cloth.

13.  

figure 6, 7, 8 and 9 - dot instead of comma

Thank you, we have revised it.

14.  

line 363 - Hz instead of Hz8?

Apologize for our typo. We have deleted “8”.

15.  

figure 9 - is there error bar missing on the last bar (counting from left to right side - C,d0.6,c0.6)?

Thank you, we have revised it.