Nanofibrillated cellulose (NFC) is drawing tremendous attention for designing new biomaterials due to their unique physico-chemical properties, abundance, and renewability. NFC, having a large number of hydroxyl groups within their structure, can be modified through numerous chemical reactions to impart specific properties for highly sophisticated applications. However, the presence of water molecules in NFC gel has been a constraint obtaining chemical reactivity, which we have determined can be overcome by using an excess of chemicals to neutralize the water of the system. Here, we report a new approach to control the chemical modification of NFC, which will greatly reduce the use of excess chemicals. NFCs of different extents of fibrillation were produced through varying mechanical energy and the acetylation of NFCs were carried out using acetic anhydride and acetic acid. FTIR spectra confirmed the successful acetylation of the NFC. We also followed a new and more accurate method to measure the degree of substitution (DS) of the acetylated NFCs. The DS of NFC reached a maximum value of 0.19 from 0 for 100 mmol excess acetic anhydride, as the fibrillation was increasing until 13 mechanical grinding stages and then dropped to lower value. The DS value never exceeded 0.5 as we targeted the surface hydroxyls only, so that the hydrogen bonds between the bulk hydroxyl groups remain unchanged and so is the fiber strength. However, the effectiveness of our approach is visible from the change of DS value with change of extent of fibrillation, which ultimately can be controlled by varying the mechanical energy during NFC production, thus, providing a new strategy for controlling the chemical consumption during reaction.

Physico-chemical factors relevant to the chemical modification of nanofibrillated cellulose

2019 Spring National Meeting

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