Compatibilized thermoplastic vulcanizate compositions
This invention relates to a thermoplastic vulcanizate having excellent elongation comprising an isotactic polypropylene matrix phase in which a cross-linked ethylene-propylene-diene terpolymer (EPDM) is dispersed, the vulcanizate comprising the reaction product of: a) 35 to 55 wt % of an ethylene-propylene-diene terpolymer (EPDM); b) 10 to 40 wt % of isotactic polypropylene (iPP); c) 0.5 to 25 wt % of a propylene-ethylene-diene terpolymer (PEDM) compatibilizer, said compatibilizer having a heat of fusion of less than 2 J/g; and d) 0.015 to 0.03 wt % of curatives; wherein the percentages of components (a) to (d) are based on the total weight of the mixture.
1. A thermoplastic vulcanizate comprising an isotactic polypropylene matrix phase in which a cross-linked ethylene-propylene-diene terpolymer (EPDM) is dispersed, the vulcanizate comprising the reaction product of:
a) 35 to 55 wt % of an ethylene-propylene-diene terpolymer (EPDM)), wherein the EPDM comprises 50 to 80 wt % ethylene;
b) 10 to 40 wt % of isotactic polypropylene (iPP);
c) 0.5 to 25 wt % of a propylene-ethylene-diene terpolymer (PEDM) compatibilizer, wherein the PEDM comprises 2 to 25 wt % ethylene and a diene content of 1 to 21 wt %, said compatibilizer having a heat of fusion of less than 0.25 J/g; and
d) 1.5 to 3.0 wt % of curatives;
wherein the percentages of components (a) to (d) are based on the total weight of the mixture.
2. The thermoplastic vulcanizate of claim 1 , further comprising at least 10 wt % of a diluent.
3. The thermoplastic vulcanizate of claim 1 , in which the EPDM comprises propylene, 55 to 75 wt % ethylene, and 2 to 10 wt % 5-ethylidene-2-norbornene.
4. The thermoplastic vulcanizate of claim 1 , in which amount of PEDM present is from 2 to 30 wt % of the amount of EPDM.
5. The thermoplastic vulcanizate of claim 1 , in which the PEDM has a Mooney Small Thin viscosity MST (5+4) @ 230° C. of from 5 to 90.
6. The thermoplastic vulcanizate of claim 1 , in which the PEDM comprises 5 to 18 wt % ethylene and 2 to 12 wt % 5-ethylidene-2-norbornene.
7. The thermoplastic vulcanizate of claim 1 , wherein the particle size dispersity index (PSDI) is less than 3.
8. The thermoplastic vulcanizate of claim 1 , further comprising clay and carbon black.
9. The thermoplastic vulcanizate of claim 1 , wherein the PEDM has no detectable heat of fusion (Hf) when measured by DSC.
10. The thermoplastic vulcanizate of claim 1 , wherein the particle size dispersity index (PSDI) is 7 or less.
11. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate has a tension set at 50% elongation of 14% or less.
12. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate has a tension set at 50% elongation of 14% or less and the particle size dispersity index (PSDI) is 7 or less.
13. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate has:
1) a particle size dispersity index (PSDI) of 7 or less;
2) a tension set at 50% elongation of 14% or less;
3) an elongation at break of 200% or more;
4) a break stress of 4 MPa or more; and
5) a tension set at 25% elongation of 7% or less.