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Published on January 1, 2006

Low Viscosity HNBR for Injection Molding Applications

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Date Published January 1, 2006

This Report has been authored by:Richard J. Pazur at Lanxess Inc.

It is well-known throughout the rubber industry that the high Mooney viscosity of commercially available HNBRs can cause processing issues, particularly during the production of injection molded parts where high shear rates are often encountered. In order to address these processing concerns, LANXESS has developed Advanced Technology (AT) based HNBRs which possess substantially lower Mooney viscosities. The newest grade in the AT family is known as TherbanŽ AT A 3904 VP (34% acrylonitrile, < 0.9 % residual double bond content and 39 MU (100°C)). This investigation shows how HNBR-AT can improve the processability characteristics of a typical 70 MU 39% ACN HNBR. Compound Mooney and scorch as well as RPA all showed better processing characteristics when using the low viscosity HNBR-AT. Mechanical properties are essentially retained with only a minor change in stiffness values observed. The narrower MWD of HNBR-AT aids in the good mechanical property retention upon blending. All other properties tested were similar to those of the higher viscosity HNBR. This study has clearly demonstrated that the low viscosity HNBR-AT can be used alone or as blend component depending on the processability and/or final vulcanizate characteristics desired by the end user.