Short-Branched Fluorinated Polyurethane Coating Exhibiting Good Comprehensive Performance and Potential UV Degradation in Leather Waterproofing Modification
Round 1
Reviewer 1 Report
The presented manuscript is focused on new short-branched fluorinated polyurethane coatings. The paper needs a minor revision.
Please support the conclusion with the results.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper presents an experimental assessment of a novel strategy for the preparation of the fluorinated polyurethanes containing short branched fluorocarbon chains, and applied in leather waterproofing.
The experimental data and the described methodologies are congruent with final targeted results however some issues should be revised by the author and some English correction should be made before this paper can be suggested for publication.
Line 90 pag. 2. Did the author measure the OH- index of the new synthesised Rf-OH to fix the correct molar ratio between the isocyanate and polyol in order to achieve the final PU?
The author should specify the final employed molar ration between TDI and Rf-OH?
Fig. 1a reports the chemical reaction scheme, the synthesis steps are not fully and congruently described within the manuscript (page 3). Please provide in the related section of the manuscript, detailed description of the reported scheme within the figure with particular attention to specify the different final products. Please provide more information of the reaction products between TDI and BDO reported in the scheme as OCN-----NCO
Line 208-209 pag 5. Please rephrase this sentence as the second part seems redundant with the first one.
Line 210, pag 5. The authors is invited to explain why the XPS experimental data of fluorine content result higher than theoretical one. Please provide analysis and augmentation to explain this result. Did the author look at the other ET:FA ratio samples?
Line 227-234. The reported results in figure 2IV are analysed in the text at line 227-234, however in my opinion, the differences of the reported images are difficult to appreciate and thus the author is invited to review the whole figure making each mapped images clearer.
Pag.7 Par. 3.3. Surface wettability. The authors report measurements of Water droplet Contact Angle (WCA) as a fundamental parameter to evaluate surface waterproofing performance and Water absorption parameter to characterize hydrophobic performance. The reported results for WCA are mainly explained relating the measured hydrophobicity to the saturation of the fluorine concentration onto the external surface of the coating as function of ET:FA ratio increasing. The water absorption curves reported in figure 3b are confusingly explained and in my opinion, not fully congruently and poorly augmented from line 257 to line 270 at page 7. In details some insights. The author refers that “Due to the existence of fluoride chain segments, the water absorption for FPU sample was smaller than the pure PU” as the “water absorption rates of FPU coatings incorporating FA gradually decreased with the increase of FA addition proportion” moreover, in particular for the ET:FA=0:1 ratio “This is also due to the low surface energy of fluorine containing chain segments migration and enrichment onto the surface”. In my opinion, the water absorption results should be more analysed and correlated to the structural morphology of the attained coatings by varying the ET:FA ration, mainly because at FA content higher that 0.5 the hydofobicity of the sample are negligibly changing as reported by fig. 3a and also for the plateau surface energy level reached as reported in fig. 2iii. The water absorption would be differentiated among the different ET:FA ratios but this is not evident if the first measuring point is after 24h ( did the author measure at soaking time less than 24h? as in my opinion the influence of flourine concentration should affect the hydrophobicity as reported which in turn whold affect the early stage of diwater diffusion mechanism); moreover, to fully analysed the achieved results reported in fig. 3b for soaking time higher than 24h, the author should provide insight of the internal PU microstructure due to the ET:FA changes otherwise the slightly variation of the hydrophobicity (as reported in fig. 3a) does not congruently support the conclusion of a completely different soaking time effect on the analysed samples.
The author should provide more insight and explanation of the water absorption results if related with the obtained results of the hydrophobicity.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The paper was correctly revised according to the indicated comments. In this form I would suggest the manuscript for publication.
