Enhanced interfacial interaction between modified cellulose nanocrystals and epoxidized natural rubber via ultraviolet irradiation

Abstract

This study aims at evaluating the reinforcement of cellulose nanocrystals (CNCs) in epoxidized natural rubber (ENR). Both CNCs and maleic anhydride-modified CNCs (M-CNCs) were prepared from Napier grass stems and characterized by various techniques (e.g., TEM, FTIR, TGA, etc.). They were incorporated into ENR latex at various loadings prior to casting, and then curing by ultraviolet (UV) irradiation. Mechanical properties of the ENR vulcanizates were finally investigated. Results revealed that the prepared CNCs had an average diameter and length of 5 nm and 428 nm, respectively. After modification, M-CNCs contained double bonds in maleate units, which could react with ENR to form covalent bonds under UV irradiation through a proposed mechanism. Regardless of the filler type, mechanical properties including hardness, modulus, and tensile strength, increased considerably with increasing filler loading. At the same filler loading, M-CNCs exhibited greater reinforcement than CNCs due to the enhanced rubber–filler interaction.

Fabrication of untreated and silane-treated carboxylated cellulose nanocrystals and their reinforcement in natural rubber biocomposites

“…However, the CrI value after the treatment slightly declined from 73.3 to 70.3%. Similar findings have previously been uncovered 33 , 42 , 43 .…”

“…XRD patterns of the samples, shown in Fig. 3 b, reveal the characteristic peaks at 2θ of 15.5°, 16.3°, 22.2°, and 34.6° corresponding to the cellulose I crystallographic planes ( ), (110), (200) and (004), respectively 32 , 33 . Owing to the progressive elimination of amorphous hemicellulose and lignin after each preparation step, the crystallinity index ( CrI ) values tended to increase, i.e., they were 57.5%, 62.0%, 62.3%, and 73.3% for Napier grass stem, alkali-treated specimen, bleached specimen, and XCNC, respectively.…”

Sustainable natural rubber composites: masterbatch development of epoxidized natural rubber grafted to designed enzymatic polysaccharides

“…27,40,41 The peaks at 872 and 1250 cm À1 are attributed to the asymmetrical and symmetrical stretching vibration of the C-O-C of the epoxidized groups in ENR chains. 26,28 For ENR-grafted glucan, an increase in the intensity of the broad peak in the range of 3000-3600 cm À1 associated with the OH peaks of glucan is observed. In addition, a new peak at 1140 cm À1 depicted an ether group that confirms the formation of chemical bonding between ENR and glucan, which was absent in the neat ENR (Fig.…”

“…[22][23][24] Additionally, the oxygenous groups of ENR make it more polar than NR, allowing it to be more compatible with polar fillers, such as glucan. For instance, the improved compatibility of ENR with polar fillers including cellulose nanocrystals, [25][26][27][28] lignin, 29 silica, 21,30 clay, 31 starch, 32 and chitosan 33 to fabricate ENR composites is reported. In this study, a high temperature and shear-mediated reaction of the oxirane group of ENR with the electronegative hydroxyl groups of glucans via a ringopening reaction to form covalent grafts is investigated.…”

Nanocellulose: A Fundamental Material for Science and Technology Applications

“…Complex structures with cellulose nanocrystals with high strength, stiffness, toughness, and hardness can be developed by this approach. Somseemee and co-workers [146] studied the effect of UV radiation on the cellulose nanocrystal's reinforcement on epoxidized natural rubber (ENR). The cellulose nanocrystals were extracted from Napier grass stems.…”