Improved aging and UV resistance of TPEs derived from "diimide-hydrogenated" emulsion SBRs containing a bound antioxidant

In our continuing efforts to both (1) exploit the versatility of our unique emulsion based diimide hydrogenation technology and (2) expand the performance range of hydrogenated‐SBR TPEs derived from this technology, we have investigated some of the physical and chemical effects of incorporating a polymer‐bound antioxidant into HSBR. A polymerizable amine‐type antioxidant was incorporated into the SBR structure using a conventional type “cold” emulsion polymerization recipe. For comparative purposes, unmodified and AO‐modified SBRs were then “hydrogenated” in their latex forms by the diimide technique to approximately the same extent. Samples of the extracted, isolated polymers were evaluated by DSC techniques to ascertain any effects of the bound antioxidant. Additionally, latex cast films of the HSBRs were evaluated for their initial and aged physical properties. The results of these studies indicate that while hydrogenation of SBR into the 80–90% range does dramatically improve its resistance to oxidation compared with SBR (without antioxidant), a further substantial improvement in oxidation resistance can be obtained at the same hydrogenation level by the incorporation of a bound antioxidant. Furthermore, because the bound antioxidant molecule is too large to be incorporated into the polyethylene‐like crystallites, it resides in the TPE's amorphous phase, where antioxidant protection is needed most, and does not appear to affect crystallite size, distribution, or overall initial TPE physical properties compared with the unmodified HSBRs.