Biomass carbon (BC) and soy protein (SP) were used
to reinforce natural rubber (NR) biocomposites. The
particle size of BC was reduced and characterized with
elemental analysis, X-ray diffraction, infrared spectroscopy,
and particle size analysis. The rubber composite
reinforced with the BC/SP and the composite reinforced
with the BC of higher carbon content show useful
tensile properties at an optimum filler fraction. The
model analysis of the stress–strain behaviors provides
insight into filler network characteristics. For the highly
filled composites, the BC have less constraint on the
polymer chains as shown by the temperature and frequency
dependent modulus as well as the model analysis
of stress softening effect. The presence of NR
protein improves the filler–polymer adhesion for the
composites reinforced with BC/SP. POLYM. COMPOS.,
34:697–706, 2013. ª 2013 Society of Plastics Engineers