Dynamic Vulcanization of NR/PCL Blends: Effect of Rotor Speed on Morphology, Tensile Properties and Tension Set

Abstract

This work aimed to study effect of rotor speed during melt mixing of natural rubber/polycaprolactone (NR/PCL) on the morphology which controls mechanical properties of dynamic vulcanizate using Luperox101 as a curing agent in NR component. The rotor speeds at 60 and 80 rpm were compared. The morphology of NR/PCL vulcanizates elucidated from SEM micrograph showed that the vulcanizates exhibited NR paticles dispersed in PCL matrix. In addition, the phase size of dispersed NR should be smaller with increasing rotor speed due to the increased shear force. This large PCL domain induced stronger strain hardening in stress-strain behavior under tension. This behavior is closed to tensile behavior of PCL and appeared at the vulcanizates. In terms of modulus, Young’s modulus was concentrated and reported. The lower degradation of PCL phase during melt mixing in the vulcanizates prepared from melt mixing at rotor speed of 60 rpm was responsible for higher Young‘s modulus than that prepared from rotor speed of 80 rpm. The tension set of NR/PCL vulcanizates prepared with rotor speed of 60 was higher than that with rotor speed of 80 rpm. It was suggested by Nakason et.al. [1] that the tension set of vulcanizates should be lower than 50 % so that they could be applied for thermoplastic vulcanizates. In this system, tension set values of the vulcanizates containing PCL 30-45 wt.% were lower than 50% in both rotor speed conditions.