Polymers 2022 , 14 , 3309
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4. Conclusions Several cationic cellulose derivatives with distinct morphologies, namely, fibers, micro- and nanofibrillated celluloses and soluble celluloses, with degrees of substitution ranging between 0.02 and 1.06, were produced by the incorporation of quaternary ammonium groups into the cellulose structure. A direct reaction with CHPTAC or a two-step reaction with Girard’s reagent T was used for cationization. Cationic micro- and nanofibrillated celluloses were produced by subsequent high-pressure homogenization. The produced samples were evaluated by LDS in terms of their potential to flocculate PCC (in terms of the average size of flocs) and were compared against a commercial CPAM. The fibrillated celluloses with a DS of 0.13 (CH0.13_F, obtained by the CHPTAC pretreatment) and 0.16 (GT0.16_F, obtained by the Girard T pretreatment) demonstrated the highest flocculation potential, being the best and second-best performing samples, respectively. The flocculation of sample CH0.13_F at dosages above 4 mg/g of PCC resulted in floc sizes greater than those obtained with CPAM. The sample GT0.16_F, independently of the dosage used (1 to 10 mg/g of PCC), always led to flocs smaller than with CPAM added at the lowest dosage (1 mg/g of PCC). Both cationic samples were further incorporated into pulp and filler formulations and were analyzed in a dynamic drainage analyzer to quantify their effects on filler retention. Compared to the reference formulation of only pulp and PCC (no retention aid), where a filler retention of ca. 43% was obtained, both celluloses were able to increase the levels of retention to ca. 61–62% (for an incorporation of 0.4 wt %), remaining, however, below the 73% achieved with CPAM (for an incorporation of 0.02 wt %). The cationic celluloses were demonstrated to be a promising new bio-based retention agent, with the potential to replace CPAM as a retention agent in papermaking, although the results of this work indicate the need for further studies in order to achieve performances similar to or better than those of the fossil-based retention agents that are used presently, and with equivalent costs. Author Contributions: Conceptualization, J.F.S.P., L.A., M.G.R. and P.J.T.F.; funding acquisition, P.J.T.F.; investigation, J.F.S.P. and L.A.; project administration, P.J.T.F.; supervision, C.P.N., M.G.R. and P.J.T.F.; writing—original draft, J.F.S.P. and L.A.; writing—review and editing, J.F.S.P., L.A., C.P.N., M.G.R. and P.J.T.F. All authors have read and agreed to the published version of the manuscript. Funding: This work was carried out under the Project Inpactus–innovative products and technologies from eucalyptus, Project N. ◦ 21874 funded by Portugal 2020 through European Regional Development Fund (ERDF) in the frame of COMPETE 2020 n ◦ 246/AXIS II/2017. The authors also want to acknowledge the Strategic Research Centre Project UIDB/00102/2020, funded by the Fundaç ã oparaa Ci ê ncia e Tecnologia (FCT), the Project ToxApp4NanoCELFI (PTDC/SAU-PUB/32587/2017, from the Foundation for Science and Technology, Portugal), and the Network CYTED Nanocelia-Transferencia Tecnol ó gica sobre Aplicaciones de Nanocelulosa en Iberoam é rica. J.F.S.P. also acknowledges the PhD grant BDE 05|POCI-01-0247-FEDER-021874. Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Conflicts of Interest: The authors declare no conflict of interest.
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