Modification Partially Hydrogenated Nitrile Rubber Via Metathesis And Its Influence On Properties

The currently commercially available hydrogenated nitrile rubber often has a high molecular weight and Mooney viscosity, which caused the processing difficulties, This paper focused on modification HNBR (residual double bond content of22.5mol%) by olefin metathesis. It was investigated that reaction solvent, catalyst type, double bonds content in polymer, catalyst loading, the polymer solution concentration and addition alkene and its loading influenced on metathesis reaction of HNBR, and characterized the product structure and dynamic properties of vulcanizates.The results showed that the metathesis reaction of HNBR can take place in THF. The Hoveyda-Grubbs type of catalyst was more efficiency and Zhan1B catalyst was highest efficiency for HNBR metathesis. Self-metathesis of HNBR with less double bonds content was harder to occur than a high double bond content of HNBR or NBR. For the9wt.%of rubber concentration, the amount of Zhan1-Bcatalyst was more than0.2phr to make the HNBR(RDB=22.5mol%) metathetic degradation.At the same rubber concentration, the molecular weight decreased with increasing amount of catalyst and narrow molecular weight distribution, and by adjusting the amount of catalyst, the different molecular weights product can be obtained. While appropriately improve the rubber concentration (9wt.%-13wt.%) can also improve the efficiency of the HNBR self-metathesis degradation and catalyst efficiency.Cross-metathesis of HNBR with alkene (1-hexene) can decrease molecular weight sharply and narrow molecular weight distribution. Comparision with self-metathesis, it had faster reaction rate and need less amount of catalyst and reaction time to get same molecular weight of HNBR.Selected reaction products were characterized by size exclusion chromatography with the simultaneous detection of intrinsic viscosity and multi-angle laser light-scattering. It was found that for the same molar masses, the self-metathesized polymer has lower intrinsic viscosities, as well as smaller distances of free chain ends than the respective cross-metathesized polymer. From these observations it was concluded that self-metathesis results in a higher portion of polymers with ring structures than polymers which were obtained by cross-metathesis in the presence of1-hexene.Modification of HNBR by Self-and cross-metathesis not only improved its processibility but also kept good mechanical properties as well as original HNBR. Dynamical mechanical properties analysis (DMA) revealed that the self-metathesized product has lower mechanical loss factor than cross-metathesized product.