The improvement of mechanical performance and water-response of carboxylated SBR by chitin nanocrystals

• Individual dispersion of chitin nanocrystals was obtained by acid hydrolysis.
• CNCs can be uniformly dispersed in the xSBR indecency of CNCs loadings.
• CNCs significantly improved the tensile strength, tensile modulus, and strain at break of xSBR.
• Water-responsive adaptive mechanical properties of xSBR/CNCs composites were found.

Carboxylated styrene-butadiene rubber (xSBR) composites with chitin nanocrystals (CNCs) were prepared by solution-casting method. CNCs prepared by acid hydrolysis show rod-like morphology with diameter of ∼15 nm and length of 200–500 nm. The hydrogen bonding interactions between the rubber and CNCs are confirmed by FTIR. Tensile testing demonstrates CNCs can significantly increase the tensile strength, tensile modulus, and strain at break of xSBR. The dispersion of CNCs is homogenous in the matrix even at high loadings. The storage moduli (E′) of the composites increase by CNCs especially at rubber region. The glass transition temperature of xSBR nearly does not change after the incorporation of CNCs. Upon submersion in deionized water, dramatic reduction of tensile modulus is observed for the nanocomposites, for example, from 31.1 to 2.8 MPa for nanocomposite containing 3 wt.% CNCs. These changes are interpreted as the formation of percolating CNCs network and the interfacial interactions in the composites.

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