High-Gas-Barrier and Biodegradable PPC-P/PBAT Composite Films Coated by Poly(vinyl alcohol)/borax Complexes
, Sheng Huang 2, Shuanjin Wang 2, Dongmei Han 1,2,* and Yuezhong Meng 1,2,3,4,*
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis article describes the preparation of PPC-P/PBAT blends for use as high barrier biodegradable packaging. By varying the PPC-P/PBAT ratio, the mixture with optimal mechanical properties was determined. By incorporating MDI as a chain extender and glycerol as crosslinking agent, the mechanical properties of the polymer blend were significantly improved and the thermal stability was increased. Tensile strength and elongation at break could be increased. The coating with PVA and borax created a composite material with good barrier properties.
The coated composite films examined are interesting in terms of their possible application as a packaging material. Unfortunately, no mechanical properties of the coated composite films are specified. Furthermore, there is no comment on the adhesion stability between the composite film and the coating. Therefore, no statement can currently be made about a possible application of the coated composite films.
The manuscript is well written. Some typos need to be corrected and incorrect terms replaced. The following comments should be considered when revising the manuscript.
1. Introduction
Line 42: Abbreviations such as PO (propylene oxide) must be explained the first time they are used.
Line 66: The borate ion B(OH)4- is negatively charged. This charge must be reported in Fig. 1 (c) for both the borate ion and the PVA/borate complex.
Lines 68, 69: The coating contains borate ions, not borax. Borax is a salt with the composition Na2B4O7∙10H2O.
Line 69: According to Fig. 1 (c), the coating in scheme (d) should be represented as a layer consisting of PVA chains linked via borate. In the illustration shown in (d) there is a borate layer on the PVA layer. What do the research results say about this?
2. Materials and Methods
Lines 87, 107: Replace the dumbbell spline with dumbbell-shaped sample.
Lines 116, 122, 124, 125: Use K/min instead of °C/min for heating and cooling rates.
3. Results
Line 191: Stretch the diagram to better see of the different maxima.
Line 194: The symbol χc in Table 1 is not explained and the values are not discussed anywhere.
Line 195: Footnote 1 is not used in Table 1. Delete them.
Lines 244/248: Replace the degree of fog with the degree of haze and change this also in Table 3.
Line 249: How thick is the coating on the composite film? Enter the missing information here.
Lines 276, 279: The abbreviations OP and OTR should be introduced upon first use.
Line 285: The specification of the units of measurement is misleading. This also applies to the axis labels in Figure 5. What do the two different thickness values mean? There is also no assessment of the water vapor permeability of the films. In addition to the information in the table, a brief statement on water vapor permeability should be added.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
Thanks for studying the PPC-P/PBAT composite films' characteristics, in search for an alternative to synthetic polymers. Manuscript is interesting and well organized. However, I have these comments that should be addressed to increase article's potential readability:
1) Lines 63-65: a further description of the characterization techniques used in the manuscript based on the particular applications targeted is recommended.
2) In lines 34-36: "According to the World Bank, global plastic waste production reached 12 % of total solid waste in 2016." A reference is suggested here, supporting this statement.
3) 2.1 section: Complete PPC-P and PBAT chemical denomination is recommended here. Same for the solvers, chain extenders, and coating materials used.
4) Line 112: "test environment" conditions (at least temperature and humidity) should be specified, provided it is stated that this is done "to eliminate the effects of temperature and humidity".
5) Macroscopic optical images are suggested, to allow the reader the opportunity of checking the film's appearance.
6) Line 128: characterizers of the metallizer (trademark, exposing time, etc.) must be revealed too.
7) If layers are intended for packaging use, not only tension is interesting, but also compression and shear. More strength experiments are suggested.
8) A colorimeter analysis is recommended.
9) Figure 2 inset's labels and scales are too small and are barely seen.
10) 3.1 section: if elastic properties of the films are compared, it may be convenient to state a table with (at least) Young's modulus measured at each sample.
11) 2.4.5 / 3.4 sections: wavelength(s) at which transparency was measured should be declared.
12) If layers are intended for packaging use, solubility measurements are considered necessary.
13) All acronyms (like "OTR" and "OT") should be defined in the text the first time they appear (not only in a Table's note).
14) Thickness measurement procedure is not described, although values are revealed in Table 4. It is recommended to include the way how these values were obtained.
15) Consider revising the title: "highly barrier", against what? (Radiation, mechanical compression force, acids...) It is suggested detailing it more. Same for "Biodegradable" statement.
16) Throughout the manuscript it is declared that films are biodegradable (even defined in the Introduction section), but no measurement is presented to prove the biodegradability of these particular blends.
Best regards.
Comments on the Quality of English Language
Typos found:
* Line 41: an "or" is missing in the substance listing.
* Line 47: sentence "And the tensile strength is greater than 37.6 MPa" should be part of another sentence.
* Lines 16, 80, and 230: extra spaces.
* Line 104: an "and" is missing at the beginning of the part of the sentence.
* Lines 270-272: consider revising English grammar here.
* Line 307: "provides" should be.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
Thanks for having reviewed the submitted comments. All of them have been addressed. However, there are few of them that it is suggested reviewing again:
6) Ion sputtering exposing time is important for reproducing the experiment. It is recommended to include it in 2.4.4 section. Intensity value declaration is also suggested.
7) If only tension is applied, this should be declared. Instead of "Mechanical properties", "Mechanical tension" should be stated throughout the manuscript.
12) Still, it is considered that solubility measurements are necessary to complete this manuscript. Measurement is not difficult at all: just weighing samples of the films before and after immersion in water for hours. In any case, if the composite film is insoluble in water, ethanol and methanol, this must be declared in the text. Nevertheless, potential readers may doubt it if no results proving this are presented.
15) It is strongly recommended to review this comment again. "Highly barrier" is considered confusing, and biodegradability is not proved in the composite.
16) Again, manuscript is not dealing with PPC-P alone, but a composite.
Best regards.
Comments on the Quality of English LanguageSome typos mentioned in the previous revision have not been corrected yet.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
