Meaning
High performance copolymers of ethylene and an alpha olefin like octene or butene provide a combination of flexibility and toughness for plastic blends. A polyolefin elastomer is typically produced using metallocene catalysts which allow for a very narrow molecular weight distribution and precise control over the density. These materials are used to modify the impact resistance of rigid plastics or as standalone resins for flexible parts.
The definition excludes traditional rubbers that require vulcanization to achieve their properties.
Modification Efficiency
Addition of these elastomers to a polypropylene matrix measurably increases the ability of the part to absorb energy. Because a polyolefin elastomer remains flexible at low temperatures, it prevents the rigid matrix from cracking in the cold. The small size of the elastomer particles ensures that the blend maintains a good balance of stiffness and toughness.
These particles act as termination sites for cracks.
Blend Compatibility
Mixing these materials with other polyolefins is straightforward due to their similar chemical structures. Since a polyolefin elastomer has a saturated backbone, it offers better weather resistance and thermal stability than unsaturated rubbers. The low density of the elastomer helps keep the overall weight of the final part down.
Good adhesion between the phases ensures that the mechanical load is transferred effectively.
Economic Impact
Selection of an elastomer affects both the material cost and the final performance of the product. While a polyolefin elastomer is more expensive than virgin polypropylene, its high efficiency means that small amounts can achieve the required impact targets. This efficiency allows for the use of regrind or lower cost resins in the rest of the formulation.
Using these materials can reduce the total cost of a component by preventing failure and reducing wall thickness.
