Improving the mechanical properties of CNF films by NMMO partial dissolution with hot calender activation

Hannes Orelma (Corresponding Author), Antti Korpela, Vesa Kunnari, Ali Harlin, Anna Suurnäkki

    Research output: Contribution to journalArticleScientificpeer-review

    11 Citations (Scopus)

    Abstract

    Reinforcing of cellulose nanofibril (CNF) films by partial dissolution with N-methylmorpholine-N-oxide (NMMO) was investigated. The method investigated is composed of impregnation of CNF film with liquid solution of NMMO followed by dry heat activation. The heat activation of the impregnated film was carried out using a heated calendering nip, which enabled simultaneous heating and compression. The partial dissolution of cellulose by NMMO caused a significant increase in the transparency of CNF film due to the decrease of film porosity and increased surface smoothness. The dry strength of the reinforced film was increased from 122 up to 195 MPa. Furthermore, the wet strength of the reinforced film was up to 70% greater than the dry strength of pure CNF film. The changes in the fibrillar structure were investigated with topographical imaging (SEM and AFM) and spectroscopically using NMR and FTIR. No significant changes in the fibril structure or cellulose morphology were observed. Moreover, the treated film resisted significant water pressure, highlighting CNF film's permanent water resistance. The partial dissolution process with NMMO was also capable of reinforcing a CNF composite film with macro scale structural elements (lyocell short-cut fibres). The strategy investigated is a robust and fast method to improve the mechanical properties of fibrillary cellulose films, allowing them utilization in applications where improved water resistance and fully cellulosic character are required properties.
    Original languageEnglish
    Pages (from-to)1691-1704
    Number of pages14
    JournalCellulose
    Volume24
    Issue number4
    DOIs
    Publication statusPublished - 1 Apr 2017
    MoE publication typeA1 Journal article-refereed

    Keywords

    • CNF
    • film
    • hot calendering
    • NMMO
    • partial dissolution

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