Homogeneous polymer blend and process of making the same
A homogeneous polymer blend comprises a thermoplastic first polymer having a crystallinity of at least 30%; and a second polymer having a crystallinity of more than 5% and being at least partially cross-linked.
1. A homogeneous polymer blend having one glass transition temperature indicated on a dynamic mechanical thermal analyzer trace of tan δ versus temperature comprising:
(a) a thermoplastic first polymer having a crystallinity of at least 30% and a melting temperature at or above 100° C., wherein said thermoplastic first polymer is a co-polymer of propylene and from 0 to about 5% of alpha-olefin comonomers, by weight of said thermoplastic first polymer; and
(b) a second polymer different from said thermoplastic first polymer and having a crystallinity less than that of said thermoplastic first polymer, wherein said second polymer being polymerized and at least partially cross-linked in the presence of said thermoplastic first polymer and at least one polyene having at least two polymerizable unsaturated groups to form said second polymer which is a polymer of propylene, 2 to 15 weight % of one or more C 2 and/or C 4 to C 10 alpha-olefins comonomers and 0.01 to 5 wt % polyene, by weight of said second polymer.
2. The polymer blend of claim 1 , wherein the crystallinity difference between the second polymer and the thermoplastic first polymer is less than 20%.
3. The polymer blend of claim 1 , wherein one, two or more of said alpha-olefin comonomers of said thermoplastic first polymer are co-polymerized with propylene.
4. The polymer blend of claim 1 , wherein said thermoplastic first polymer has a melting point between about 100° C. and about 170° C.
5. The polymer blend of claim 1 , wherein said thermoplastic first polymer has a melt flow rate of 2000 dg/min or less as measured according to ASTM D-1238 (2.16 kg, 230° C.).
6. The polymer blend of claim 1 , wherein said thermoplastic first polymer has a melt flow rate of 100 dg/min or less as measured according to ASTM D-1238 (2.16 kg, 230° C.).
7. The polymer blend of claim 1 , wherein said alpha-olefin comonomer of said second polymer is ethylene.
8. The polymer blend of claim 1 , wherein said second polymer comprises at least a fraction which is insoluble in xylene.
9. The polymer blend of claim 8 , wherein said fraction insoluble in xylene comprises at least 4 wt % of the polymer blend.
10. The polymer blend of claim 1 , wherein said polymer blend is substantially free of processing oil and/or a curative agent.
11. The polymer blend of claim 1 , wherein said polymer blend has a tensile strength at break of 0.5 MPa or more as measured by ISO 37 at 23° C.
12. The polymer blend of claim 1 , wherein said polymer blend has a Shore hardness of 30 A to 90 D as measured by ISO 868.
13. The polymer blend of claim 1 , wherein said polymer blend has an ultimate elongation of 20% or more as measured by ISO 37.
14. The polymer blend of claim 1 , wherein said polymer blend has a compression set of 90% or less as measured by ISO 815A.
15. The polymer blend of claim 1 , wherein said polymer blend has a tension set of 100% or less as measured by ISO 2285.
16. The polymer blend of claim 1 , wherein said polymer blend has an oil swell of 500% or less as measured by ASTM D471.
17. The polymer blend of claim 1 , wherein said alpha-olefin comonomers of said thermoplastic first polymer contain 2 or from 4 to 12 carbon atoms.