Characterization of deproteinized natural rubber modified via graft copolymerization with styrene/acrylonitrile and reinforced with cellulose nanofibers

Natural rubber (NR) and cellulose are promising biopolymers for the development of sustainable materials. Natural rubber has several superior properties, such as outstanding properties and resilience. Moreover, the greatest advantage of cellulose nanofibers (CNFs) is their high mechanical strength, which is very suitable for making reinforcement domains on other polymers. However, the disparity in polarity between NR and CNFs significantly influences the properties of the resulting composite materials. This study investigated the graft copolymerization of styrene/acrylonitrile onto deproteinized natural rubber (DPNR) to increase its polarity, thermal stability, and mechanical properties. The composite materials were prepared from natural rubber grafted with CNFs via CNF dispersion in latex using ultrasonic waves with the aim of improving the mechanical properties of NR. The mechanical properties of the materials were studied via tensile testing, where the tensile strength of the composite with the graft copolymer matrix domain at a CNF of 1.0 wt.% (5.09 +/- 0.49 MPa) was three times greater than that of the composite with DPNR (1.6 +/- 0.14 MPa). The dispersion capacity of CNFs within various rubber matrix domains was assessed by analyzing morphological alterations with scanning electron microscopy. The increase in the thermal properties of the resulting products was verified via thermogravimetric analysis.