Self-reinforced composites obtained by the partial oxypropylation of cellulose fibers. 2. Effect of catalyst on the mechanical and dynamic mechanical properties

Abstract

This work describes the partial oxypropylation of filter paper cellulose fibers, employing two different basic catalyst, viz., potassium hydroxide and 1,4-diazabicyclo [2.2.2] octane, to activate the hydroxyl groups of the polysaccharide and thus provide the anionic initiation sites for the ''graftingfrom'' polymerization of propylene oxide. The success of this chemical modification was assessed by FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis and contact angle measurements. The study of the role of the catalyst employed on the extent of the modification and on the mechanical properties of the ensuing composites, after hot pressing, showed that both the Brønsted and the Lewis base gave satisfactory results, without any marked difference.

Review: current international research into cellulose nanofibres and nanocomposites

“…The concept of all-cellulose composites has been explored for a wide range of cellulose materials including wood pulp fibres [250,251], filter and Kraft paper [252][253][254][255], MCC [256][257][258][259][260], sisal [261,262], ramie [263], regenerated cellulose (Lyocell) and cellulose fibres spun from an anisotropic phosphoric acid solution (Bocell) [264], and BC [265]. These studies showed great promise.…”

Partial periodate oxidation and thermal cross-linking for the processing of thermoset all-cellulose composites

“…In the first processing strategy there is a partial or total dissolution of cellulose followed solvent removal, cellulose regeneration of the dissolved part and drying [8,10e13]. The second route relies on cellulose derivatization: a thermoplastic cellulose matrix is simply formed by benzylation [14,15], oxypropylation [16,17] or esterification [18,19]. The etherified or esterified amorphous cellulose derivatives are then hot-pressed with unmodified cellulose to form the ACCs.…”

All‐Cellulose Composites

“…Benzylated fibers show the formation of a thermoplastic region surrounding the fiber core [141][142][143][144]. This effectively grafts a thermoplastic polymer matrix onto the outer surfaces of the fibers, with the amount measured by the weight gain [146][147][148]. Fiber volume fractions of up to 40% have been achieved using this method.…”

“…The composites are then finally formed by hot pressing [141][142][143][144]. de Menezes [148] et al report that the amorphous regions of the cellulosic materials are more prone to modification than crystalline regions, while the degree of modification is dependent on the amount of PO used [147]. Lu et al reported that the rate of benzylation is not strongly dependent on the wood source, but rather on the amounts of NaOH and benzyl chloride (C 6 H 5 CH 2 Cl), processing temperatures, and reaction times [141][142][143]145].…”

“…Fiber volume fractions of up to 40% have been achieved using this method. As for benzylated cellulose, oxypropylated cellulose can be hot pressed to form a composite film, with fiber fractions ranging from 10 to 40 vol% [141][142][143][144][146][147][148]. Increasing the degree of benzylation of cellulosic material leads to a decrease in crystallization due to disruption of the hydrogen bonds within the cellulose molecules, also reducing the final mechanical properties.…”