Thermoplastic polymer blends comprising EPDM and EP

DETAILED DESCRIPTION The thermoplastic polymer blends of this invention comprise a physical mixture of two polymer components and, optionally, a third polymer component; i.
e.
, (1) at least one ethylene-propylene-diene (EPDM) polymer containing about 63 to about 85 wt.
% ethylene, and having an unstretched crystallinity from about 1 to about 20 wt.
%, and a Mooney viscosity from about 25 to about 110 (ML 1+8 at 125.
degree.
C.
), (2) at least one ethylene-propylene (EP) copolymer having ethylene content, unstretched crystallinity, and Mooney viscosity within the above ranges, and (3) optionally, at least one polyethylene (PE).
The above polymers are mixed in a range from about 5 weight parts to about 500 weight parts of EP copolymer per 100 weight parts of EPDM polymer.
Similarly, PE when used may be mixed in a range from about 5 weight parts to about 200 weight parts per 100 weight parts of EPDM polymer.
Excellent results are obtained using a range of EP copolymer from about 20 weight parts to about 300 weight parts per 100 weight parts of EPDM.
Excellent results also are obtained using PE as an optional third polymeric blend component in a range from about 10 weight parts to about 100 weight parts per 100 weight parts of EPDM.
The polymer blends are truly thermoplastic, having excellent strength and structural stability at ambient temperatures, as well as easy processability at temperatures above about 120.
degree.
C.
A smooth roll is formed in milling operations at such temperatures, and the blends are readily extrudable and moldable, having good flow properties.
Formed items made from the blends are reprocessable.
In contrast to the thermoplastic blends disclosed in U.
S.
Pat.
Nos.
3,785,643 and 3,806,558, the polymer blends of the present invention do not need curing or crosslinking agents to effect partial cure of the polymer components, particularly the EPDM polymer.
Ethylene-Propylene-Diene (EPDM) Polymers The ethylene-propylene-diene (EPDM) polymers employed have unstretched crystallinity ranging from about 1% to about 20% based upon the weight of the EPDM polymer, as well as Mooney viscosity from about 25 to about 110 (ML 1+8 at 125