Keltan 6251A, A Versatile Sponge Grade Combining Easy Processing with Excellent Physical Properties

Keltan 6251A, A Versatile Sponge Grade Combining Easy Processing With Excellent Physical Properties.

Demands placed on the cost, performance and aesthetics of automotive sponge seals over the past decade have steadily increased.  Most automotive sponge formulations use medium to high molecular weight EPDM polymers that must be dispersed in low viscosity matrices designed for low door closing efforts.  Efficient and economic mixing of these low viscosity automotive sponge formulations is relatively difficult to achieve.  Long mixing times are often necessary to achieve the high quality surface finish of extruded profiles and in many cases a 2-step mixing process is still required to attain expected dispersion levels and to minimize scrap.  Due to the extreme demands placed on the cost, performance and quality of automotive sponge, suppliers have little opportunity for improvement.  For this reason DSM Elastomers recently embarked on the design, development and commercialization of a new amorphous, high molecular weight, high ENB sponge grade, Keltan® 6251A.  The high molecular weight provides excellent physical properties and collapse resistance while the high level of ENB allows ultra fast vulcanization. The incorporation of controlled long chain branching (CLCB) in the polymer microstructure provides an optimal balance of processing and physical properties.  With 13 wt% of extender oil, Keltan® 6251A facilitates improved dispersion when compared to polymers of similar molecular weight, providing the opportunity for more economic single stage mixing combined with high quality surface finish.  Versus polymers of lower molecular weight, Keltan® 6251A provides the opportunity to reduce cost by extending total loading without sacrificing properties or quality.  In this paper it will be demonstrated that Keltan® 6251A is a highly versatile and flexible polymer that can offer significant improvement in mixing performance, cost and/or surface quality, when compared against typical sponge grades and recipes utilized in the market today.