Characterization of Cellulose Microfibrils Obtained from Hemp

Microfibrillated cellulose was extracted from hemp fibres using steam explosion pretreatment and high-intensity ultrasonic treatment (HIUS). The acquired results after steam explosion treatment and water and alkali treatments are discussed and interpreted by Fourier transform infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) was used to examine the microstructure of hemp fibres before and after each treatment. A fibre size analyser was used to analyse the dimensions of the untreated and treated cellulose fibrils. SEM observations show that the sizes of the different treated fibrils have a diameter range of several micrometres, but after HIUS treatment fibres are separate from microfibrils, nanofibres, and their agglomerates. 1. Introduction Hemp fibres have high strength, low density, and high sustainability; therefore they are used as reinforcement in composite materials. This usefulness of cellulose fibrils is because small fibrils have better mechanical properties than the individual macrofibres. Within their structure, small fibrils include more cellulose crystals, having a higher elastic modulus than fibres, which contribute to their increased strengths [1]. Microfibrillated cellulose (MFC) is cellulose fibril aggregates obtained through disintegration of the cell wall in cellulose fibres [2]. The diameter of MFC fibrils is usually at the range of 10–100？nm and can be up to several micrometres in length, depending on the preparation methods and material source [3]. This paper compares the preparation of cellulose micro- and nanofibers obtained from hemp bast fibres and shives using steam explosion and high-intensity ultrasonication treatments. The steam explosion (SE) autohydrolysis is currently comprehensively studied as a promising green pretreatment technology [4, 5] to obtain microfibrils of cellulose and also to remove noncelluloses constitutes—lignin, hemicelluloses, pectins, and waxes. The high-intensity ultrasonication technique is an environmentally benign method and a simplified process that conducts fibre isolation and chemical modification simultaneously and helps significantly reduce the production cost of cellulose nanofibre and its composites [3]. HIUS creates cavitation and high vibrational energy in the suspension, resulting in the separation of hemp cellulose micro- and nanofibre bundles and agglomerates [6]. In the present work SE and HIUS will be combined to obtain MFC fibrils. 2. Materials and Methods Dew-retted hemp fibres of local variety “Purini” and shives of local variety “Bialobrzeskie” grown on the