8
Figure 7 shows the SEM micrograph of the TPVs. For all TPVs, two-phase morphology was clearly
observed with micron size spherical domains of the dispersed vulcanized ENR/EVA phase in the PP matrix. It was
seen that the particle size of rubber domains were changed with ENR/EVA the blend proportions. That is, the size of
domains decreased with the content of EVA in a range of 15 to 30 wt% in the blends. Furthermore, the TPVs of
ENR/EVA/PP at 30/30/40 blend ratio showed smallest rubber particles dispersed in the PP matrix. This may be
attributed to an increase of shear and extensional viscosity of the vulcanized rubber domains. The extensional flow
was gradually dominated with increasing mixing time and hence the rubber phase was broken to be droplets dispersed
in the PP phase. Larger dispersed vulcanized rubber domains with lower interfacial areas and hence higher surface
energy were observed. As a result, poor dispersion and lower interfacial adhesion of the ENR/EVA domains led to
poor mechanical strength.
Conclusion
The dynamically cured ENR/EVA/PP blends with the various of ENR/EVA ratio were prepared and their
properties were investigated. It was found that mechanical properties (i.e., tensile strength, elongation at break),
thermal properties and aging properties of TPVs increased with the increasing of EVA proportion, while, storage
modulus and complex viscosity were decreased. Furthermore, the TPVs of ENR/EVA/PP at 30/30/40 blend ratio
showed smallest rubber particles dispersed in the PP matrix.
Acknowledgements
We are grateful to the Center of Excellence in Natural Rubber Technology (CoE-NR), Graduate school and
the government budget with Grant No. SAT5211990098c for financial support.
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