Correlations Between Crystallinity, Rheological Behavior, and Short-Term Biodegradation for LDPE/Cellulose Composites with Potential as Packaging Films
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe title must be changed to reflect the content of the study clearly. Also, these types of films might act as potential packaging films, no such application has been specifically evaluated in this manuscript. I suggest as title: “Correlation between crystallinity and rheological behavior with short term biodegradation for LDPE/Cellulose Composites as potential Packaging Films”
The names of the authors need to be revised for a clear delimitation of surname and name, each is written differently (with small letters or dots…), as well as the affiliation, as both belong to University of Babilon (?).
English language and grammar must be corrected all over the manuscript, as many phrases have no meaning or do not contain the correct verbs.
e.g.: "after adding different natural fillers, which is sustainable, compatible, and biodegradable natural polymers”, "“X-ray diffraction and degradation tests at short period carried out in soil with a pH of 6.5 and 50% humidity at 27°C.”, "shear thinning behavior dominant during viscosity curves.”, “The curve fitting was proved that the suitable model for all flows of the composites melts was power law .”, “The molecular weight and cohesive structure proportion to the viscosity at lower shear rate”, “The lower of viscosity” etc
As melting temperature of LDPE is usually around 110 °C, please explain the use of 190 °C for mixing LDPE with biomass or 170, 190,and 210 °C for capillary rheometer tests, such high temperatures might affect the biomass during processing.
Please explain the part referring to XR-ray diffraction in “X-ray diffraction and degradation tests at short period carried out in soil with a pH of 6.5 and 50% humidity at 27°C.”
The innovation of this study must be clearly stated at the end of Introduction.
Please explain how a twin-screw extruder was used for “The films were prepared hot pressing” and not a normal press.
If “The cellulose additives (CNC, sawdust, powder cellulose) were mixed with (30ml) distilled water and dispersed”, then wet cellulose has been directly mixed with LDPE, it clearly affects the processing, known that the moisture affects mixing hydrophobic with hydrophilic phases.
If only very thin composite films of about 25 micrometers were obtained, please explain how the capillary rheometer was fed with the samples.
It is clear that a piece of film of (1 × 1 cm²) with 25 micrometer thickness does not load 2 grams, could you please explain your affirmation?
As LDPE is nonpolar, please explain “cellulose…….interaction with LDPE”, as well as “hydrogen bonding between cellulose hydroxyl groups (-OH) and LDPE chains”.
Please plot Figure 1 in logarithmic scale on both axes.
All SI units should be properly written with capital letters following all values in the text (pa.s, c). What is (p,a)?
No numbers without unit should appear (85100,7540, and 7070 at 210 °C for CNC, sawdust,…), “10 shear rate”.
Please clearly explain why “Higher viscosity induces fewer biofilm attachment sites which reduced microbial colonization”, while viscosity value is assessed in melt state, and antimicrobial activity is evaluated for solid or liquid materials.
Please offer a clear scientific meaning of the affirmations in the manuscript, not only increasing or decreasing, e.g. clarify why “LDPE/CNC melts indicates higher viscosity at low shear rate for all ratios compared with the other melts.”
Please move XRD results discussions before rheology as crystallinity explains the rheological behavior.
The authors should state which “Rheology App. Program” were they using for calculations.
Replace Herschel Buckley with the correct Herschel–Bulkley model.
References are required in section 3.1.2. Rheological Model for all models, equations and affirmations regarding low and high n and k related to interactions and “microbial attack”.
Please clarify exactly which composition of LDPE/CNC was evaluated for XRD.
Magnification bars in Figure 6, as well as the method description and instrument (microscope type) used for morphological evaluation are required.
What is LDPS in conclusions?
Comments on the Quality of English LanguageEnglish language and grammar must be corrected all over the manuscript, as many phrases have no meaning or do not contain the correct verbs.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsDear Authors,
Thank you for your effort in correlating the rheological properties of LDPE/cellulose composites with their biodegradability behavior.
A) Formatting, Punctuation, Parallel Structure, and Spelling
Line 5: Capitalization of the second author's name.
Line 17: Correct notation should be 190°C.
Temperature Notation: Always use “°C” for temperature values. The degree symbol frequently appears misplaced in the middle of the line (e.g., Line 19).
Line 25: The sample notation alternates between LDPE/filler and LDPE\filler—please ensure consistency throughout the manuscript.
Line 28: The sample notation alternates between LDPE/filler and filler/LDPE—please adopt a uniform notation across the manuscript.
Lines 35, 36, 39: Remove unnecessary spaces within words.
Line 94: The term fillers should be consistently labeled—currently, it appears as cellulose, cellulose powder, and powder, which may be confusing for readers.
Line 100ff: Ensure that there is always a space after a dot.
Line 107: Clarify whether particle size is in the range of 10 to 20 nm, as the notation 10_20 is not clear. Additionally, the meaning of ",300_900 nm, length" should be specified more clearly.
Line 136: Remove the unnecessary closing parenthesis “)”.
Line 141: Ensure that the degree symbol (°C) is properly formatted as a superscript.
General Punctuation: Insert spaces after commas consistently throughout the document.
Line 164: The notation pa.s should follow correct SI unit conventions. If referring to Pascal-seconds, use Pa·s without spaces between "P" and "a". Maintain proper capitalization and formatting of units throughout the manuscript.
Line 164: The degree symbol (°C) is incorrectly formatted—please correct it.
Line 189: The section heading contains a colon—please clarify if this is intentional or an error.
Line 200ff: The term viscosity consistency k appears both in lowercase and capitalized—please standardize its formatting.
Line 200ff: The flow index n appears both with and without parentheses—please ensure uniform notation throughout.
Line 280ff: The first paragraph of the conclusion is formatted differently from the rest of the text—please ensure consistency.
B) Content-Related Remarks
Line 46: A material can be either bio-based, biodegradable, or both. The third option should also be explicitly mentioned for clarity.
Line 67ff: The authors discuss the influence of crystallization behavior; however, this topic is not revisited later in the manuscript. Additionally, crystallization behavior is generally undesirable for packaging materials. Consider whether this section is necessary.
Line 73: The statement “…low interfacial adhesion…” requires a citation to support this claim.
Line 113: The term “…hot pressing…” should be omitted, as it does not contribute additional information.
Line 118ff: This paragraph describes the pretreatment of the material before processing. To maintain a logical flow, it should be moved before the processing section (Line 113).
Line 118ff: Only sawdust was dried before processing. Why were the other fillers not subjected to the same drying process? How was it determined that drying for 2 hours at 60°C was sufficient? What is the rationale behind drying the material first and then reintroducing water? Please clarify.
Materials, Equipment, and Software: Always specify "TYPE (Manufacturer, Country of Origin)" for all materials, equipment, and software used to ensure full transparency and reproducibility.
Line 136 (Rheological Measurements): How many times were the rheological tests repeated? Were reproducibility measurements performed? Provide statistical validation to confirm the reproducibility of the results.
Line 138 (Crystallinity Index, CrI): Why was CrI selected as a parameter? Since it represents the ratio of two crystalline peaks, what specific information does it convey? Typically, this type of calculation provides insights into crystalline orientation, but in the manuscript, it is incorrectly interpreted as a measure of crystallinity degree. Either revise the interpretation or reevaluate the calculations. The cited reference focuses exclusively on cellulose analysis. Since the composite primarily consists of LDPE, please reference a study that evaluates LDPE or PE/cellulose composites.
Line 140 (XRD Measurements): How many times were the XRD experiments repeated? Were reproducibility measurements conducted? Provide statistical validation to confirm the reproducibility of the results.
Equation 1: The results presented in Table 3 are not derived from Equation 1. Additionally, based on Figure 4, CrI would always be negative, which suggests an error in the equation. Please verify and correct the formula.
Line 146ff (Testing Location and Soil Conditions): Specify the exact testing environment: Were the degradation tests conducted outdoors or in a controlled laboratory setting? Provide detailed information on the soil type: Was it humus-rich or sand-rich? Report the initial soil moisture content and explain whether it was monitored and adjusted throughout the experiment. Were the biodegradation tests conducted in accordance with a standardized protocol? If so, please specify the standard used. If no standardized method was followed, justify the deviation—there are numerous existing standards for such analyses.
Line 169: The statement “…higher viscosity…” must be supported by a citation.
Figure 1: Ensure that unit notation is correct— Pascal (Pa) should be capitalized, while seconds (s) should remain lowercase. All graphs should be plotted in a double-logarithmic scale to enhance the visibility of differences.
Figure Positioning:
- Figures 1 and 2 should not be placed consecutively—rearrange for better readability.
- The same applies to Figure 3 and Table 2—adjust the layout to improve document structure.
Table 2: The flow index (n) decreases in the first step from 170°C to 190°C for all formulations and then increases from 190°C to 210°C. Could this phenomenon be attributed to sample preparation, considering that the specimens for these tests were manufactured at 190°C? Please verify.
Line 209ff: This section requires appropriate citations to support the statements.
Line 231: The citation is incorrect, as the referenced publication only reports on CNC measurements and does not include PE. Please correct this.
Line 232: Use only LDPE as the abbreviation. Abbreviations should be introduced at their first occurrence, and LDPE has been mentioned earlier in the text.
Line 235: This statement is incorrect—see the previous explanation regarding Equation 1. Please revise.
Line 238: This statement also requires verification. Please ensure accuracy.
Line 240: It is more plausible that the nucleating effect of the filler increases crystallinity, which in turn enhances morphological order. The structure of the filler itself does not directly contribute to this effect. Please revise the explanation accordingly.
Line 247: Which samples were subjected to aging? At what temperature were these samples processed? Given that the rheological investigations were conducted at three different test temperatures, are all of them necessary for the analysis? Please justify.
Line 253ff & Figure 5: How is LDPE degradation observed after 30 days? The observed mass loss is lower than the filler content, suggesting that only the filler degraded. This assumption is further supported by the images in Figure 6. Consequently, the claim that LDPE itself becomes more biodegradable is not substantiated. How was this degradation process investigated and quantified? Please provide supporting data.
Line 300ff: Critical information is missing in almost all sections. Please provide comprehensive details to ensure clarity and reproducibility of the findings.
Author Response
Please see the attachement
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript studied “the Biodegradation of LDPE/Cellulose Composite Packaging Films in a Short Period through Rheological Behavior”, so many format errors, please double check your manuscript before submitting.
- Line 19; 210 oC It seems that it is not from word symbol
- CNC/LDPE should be LDPE\CNC
- Line 93: 2.5,5 -> Please leave a space between 2.5 and 5.
- Line 97: 170,190,210 C,
- ρ = 250 kg/m3 -> 3 should be superscript.
- 10_20 nm wide,300_900nm > 10-20 nm wide, 300-900 nm, Table 1,
- LDPE-g-MA you can write it as LDPEgMA
- Cellulosewt -> Cellulose wt
- Table 1.L1,L2, and L3 mean LDPE _> Table 1, L1, L2, and L3
- (H-4325U.S.A) -> (H-47325, U. S. A)
- Please a space between value and unit. Like 60°C -> 60 °C
- Line 158: LDPE .The -> LDPE. The
- s^-1 -> 1/s is much easier.
- Line 162: 5, 10, and 2.5%, -> wt%.
- Please use log scale both on x and y axis on Figure 1. Then viscosity curves would be a straight line. And the slope of the line is the power law n.
- Flowindex (n) Consistencyindex (k ), please leave a space
- Line 195: viscosity (P,a.s) -> (Pa*S); shear stress (p,a) -> (Pa)
- Line 277: composit es
Author Response
Please see the attachement
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors replied to the comments but did not modify the revised manuscript as mentioned in their responses. Therefore, the following changes are still necessary:
Although required before, the authors should explain how “X-ray diffraction…was conducted in soil“, as expressed in “X-ray diffraction analysis and short-term degradation tests were conducted in soil”. Revision is necessary for this phrase.
Correct re-numbering is necessary for the Figures (e.g. Figure 4. should be Figure 1 and so on).
The authors did not revise the manuscript, but they were replying DONE to my comments, thus:
- Comment: Replace Herschel Buckley with the correct Herschel–Bulkley
Response: done. Line 218
- Comment: No numbers without unit should appear (85100,7540, and 7070 at 210 °C for CNC, sawdust,…), “10 shear rate”. Response: done.
Again: all numbers require units in discussions and text. What is “85100,7540, and 7070’? Units for 10 is also necessary in “10 shear rate”.
- Use of “stronger hydrogen bonding between cellulose hydroxyl groups (-OH) and LDPE chains” is incorrect. As the authors explained in their responses to my comments, the sentence requires adequate revision.
- Logarithmic axes with base 10 require axis numbered with power 10 (e.g. 100, 101…), not found in the revised Figure 1, therefore correction is still needed.
- Comment: References are required in section 3.1.2. Rheological Model for all models, equations and affirmations regarding low and high n and k related to interactions and “microbial attack”.
Response: Rheological and mechanical properties of cellulose/LDPE composites using sustainable and fully renewable compatibilisers, November 2019, Journal of Applied Polymer Science 137(22):48744
No reference(s) has/have been introduced in the revised text as requested in my comment for the models mentioned by the authors in their specific study (Power law, correct Herschel Buckley, Caisson, 220 and Bingham), equations and affirmations regarding low and high n and k. The reference [16] mentioned above is not relevant. Therefore, other references are still necessary.
The authors' response “Crystalline Nanocellulose (CNC) has a highly ordered, rod-like structure with a high aspect ratio, which increases its surface area and enhances interactions with the polymer matrix. These rigid CNC particles create a physical barrier that restricts the movement of polymer chains, particularly under low shear conditions, increasing melt viscosity.” should be introduced after “The LDPE\CNC melts indicate higher viscosity at the low shear rate for all ratios 215 compared with the other melts.”
Comments on the Quality of English LanguageThere are still phrases with no correct meaning, revision is still necessary.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThere is nothing more...well done.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThank you for your revisions, however, still have one problem of viscosity curves.
No need of log(viscosity) and log(shear rate) on Viscosity curves (Figure 1), just use original captions (Apparent viscosity (Pa*S) and Shear rate(1/s)). And your scale still looks linear. Plot software, like excel, origin, and Sigmaplot has this function. Reader can understand that. Like the following figure.
Comments for author File: Comments.pdf
Author Response
Please see the attachment
Author Response File: Author Response.pdf
