Torrefaction of Coffee Husk Flour for the Development of Injection-Molded Green Composite Pieces of Polylactide with High Sustainability
, Octavio Fenollar 2, Yesid J. Rueda-Ordóñez 1 and Sergio Torres-Giner 3,*Round 1
Reviewer 1 Report
The manuscript entitled „Torrefaction of Coffee Husk Flour for the Development of Injection-Molded Green Composite Pieces of Polylactide with High Sustainability needs minor revision. The literature review should be extended about information related to the chemical composition of coffee husk flour and torrefied coffee husk flour. Especially the content of cellulose, lignin, and hemicellulose should be given.
Author Response
The chemical composition of coffee husk, including the content of cellulose, lignin, and hemicellulose, was added in the Introduction, please see page 2, lines 77-81.
Reviewer 2 Report
The effects of untorrefied and torrefied coffee husk flours on mechanical and thermal properties were investigated. It was found that torrefied coffee husk flour can be used as an effective renewable additive to PLLA. The experiments are well-designed and the manuscript is well-written. The revision based on the following comments are recommended.
(1) The incorporation of additives containing water can cause the molecular weight decrease of PLLA and affects the properties of composites. For your reference please see Polymer 2007, 48, 4213-4225. In the present study, low mechanical properties of untorrefied coffee husk flours can be due to the higher content of water, which should have caused the larger decrease in molecular weight during processing at high temperature and could have decreased the mechanical and thermal properties. This point is recommended to be added to the manuscript.
(2) In addition to the barrier effect of the additive on thermal degradation monitored by TG, the additive can have the chimney effect (please see Polymer 2007, 48, 4213-4225). This effect is recommended to be discussed, if possible.
(3) Please specify the number- or weight-average molecular weight, polydispersity index, and D-lactic acid unit fraction of PLLA used in the present study.
Author Response
(1) We thank the reviewer for this comment. We have added the potential effect of the filler moisture on the hydrolysis of PLA in page 6, lines 235-238, and the reference (see new reference 57)as a possible explanation for the lower mechanical properties of the PLA/CHF composites.
(2) We have also added and commented “chimney” effect in page 10, lines 375-377, during the analysis of the thermal properties. We thank the reviewer again for this comment.
(3) The requested information was added in the experimental part, please see section 2.1 in page 3.
