2
Introduction
Thermoplastic elastomers (TPEs) also play a more and more important role in the polymer industry due to
their good processability and their elastomeric properties. TPEs can be broadly classified into two groups: block
copolymers and rubber–plastic blends. Thermoplastic vulcanizate (TPV) or dynamic vulcanizate (DV) is a class of
TPE based on rubber and thermoplastic compositions. where the rubber phase is dynamically vulcanized (Legge
et
al
., 1987). Epoxidzed natural rubber (ENR) is resistant to attack by ozone, oxygen and weather. In addition, ethylene
vinyl acetate (EVA) copolymers are randomly structured polymers which offer excellent ozone and weather resistance
and have remarkable mechanical properties (Dick, 2001). There have been only a few publications that deal with
rubber blends based on EVA and EVA/ENR (Zurina
et al
., 2008). Furthermore, these no evidence for preparation of
TPE material based on blending of these two rubbery materials with thermoplastics. Therefore, in this work,
mechanical, aging, thermal and morphological properties of thermoplastic vulcanizates based on ENR/EVA/PP
blends were investigated.
Material & methods
Material
Polymer used were epoxidized natural rubber with 25 mol% of epoxide groups (ENR-25, Muang Mai
Guthrie, Thailand), ethylene-vinyl acetate copolymer with 28% vinyl acetate content (EVA-28, TPI Public, Thailand)
and polypropylene with MFI of 12 g/10min at 230°C (P700J, Thai Polypropylene, Thailand). The compounding
ingredients were precipitated silica (Untrasil VN3, Dugussa, Germany), vinyltrimethoxy silane (Silquest A-171, GE
Advanced Materials, USA), hydroxylmethylol phenolic resin (HRJ-10518, Schenectady International, USA), stanous
chloride (Ajax Finechem, Australia) aromatic oil (A-20, Caltex, Thailand), dicumyl peroxide (DCP, Wuzhou
International, China), Trimethylolpropane trimethacrylate (TMPTMA, Nanthong Litian Chemicals, China)
Preparation of thermoplastic vulcanizates
ENR/EVA were first compounded using an internal mixer at 60°C and a rotor speed of 60 rpm using
compounding formulations as shown in Table 1. Thermoplastic vulcanizates of ENR/EVA/PP blends were prepared
via dynamic vulcanization during melt mixing using an internal mixer. Mixing was performed at 160°C and a rotor
speed of 60 rpm. PP was first added into the mixing chamber and mixed for 5 min, then the compatibilizer (i.e.,
phenolic modified polypropylene, PhHRJ-PP) was fed to the molten PP and continued mixing for 2 min. The
compound ENR/EVA blends were then added into the mixing chamber. After 2 min, the peroxide curative (i.e.,
dicumyl peroxide) was then added and continued mixing until reacting plateau mixing torque. The blend products
were then pelletized for injection molding process.
