Abstract
A comparative study was conducted for three natural rubber (NR) composites: one containing raw jute fibers, one containing bleached jute fibers, and one containing cellulose nanocrystals (CNCs). The composites were prepared by adding each filler at 5 or 10 phr to the latex before chemical coagulation, and the composites were processed in a two-roll mixing mill. The mechanical, thermal, and vulcanization properties of the prepared composites were then determined. The NR stiffness increased with increasing fiber content, particularly when bleached fibers were added, as evidenced by the increased elastic moduli, maximum torques, glass transition temperature, and crosslinking density. Scanning electron microscopy showed agglomerates in the composite with 10 phr CNCs, which led to poorer mechanical performance compared to that of the bleached fiber-reinforced composite (10 phr). On the other hand, the addition of CNCs to the NR increased the cure rate index, thereby significantly advancing the optimum vulcanization time.
Highlights
Natural rubber (NR) is the only elastomer that is extracted from a renewable source (Hevea brasiliensis)[1]
A comparison of the results shows that, as expected, the acid hydrolysis process helped reduce the size of the fibers, reaching an average diameter of 16 ± 4 nm and a length of 414 ± 72 nm, consistent with those reported in literature for cellulose nanocrystals[30,31]
The jute fiber bleaching process proved to be efficient, as the morphological analysis indicated that the treatment helped remove the solids from the surface of the fibers
Summary
Natural rubber (NR) is the only elastomer that is extracted from a renewable source (Hevea brasiliensis)[1] It is an important elastomer, with interesting properties compared to synthetic rubbers, such as high mechanical strength, elasticity, flexibility, resilience, and abrasion resistance[2,3]. To develop sustainable composite materials[5], fillers extracted from renewable sources, such as natural fibers, can be used[6] These have several advantages over commercial synthetic fillers[7,8] (low cost, biodegradability, and attractive mechanical properties such as tensile strengths comparable to those of carbon and glass fibers). Mercerized and/or bleached fibers can be applied as a reinforcement for different types of polymer matrices[14,15,16], increasing the modulus of elasticity by at least 20%
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