Seals, gaskets and o-rings

As a result of recent developments in technology, the demand for high-performance elastomers (HNBR, FKM, ACM, AEM, ECO) in automotive and industrial applications (seals, hoses, membranes, O-rings etc.) has increased considerably. In order to develop efficient formulations for seals, the compound developer needs to consider several aspects – such as processing, the curing process and performance in aggressive media – all of which must comply with the specifications laid down by the automotive industry. Each seal has its own specific property profile. It is the job of the designer and compound developer to make the right choice from the wide range of polymers and chemicals available. Rhein Chemie therefore provides solutions to all kinds of problems that can arise during the manufacturing process. .... Show more Show less

Hydrogenated nitrile-butadiene rubber (HNBR) is commonly used in automotive applications involving aggressive fluids and high temperatures. For this high-performance elastomer, Rhein Chemie provides a complex system comprising antioxidants, activators and co-agents. The antioxidants recommended for this polymer are Rhenofit® DDA-70 and Rhenogran® ZMMBI-50. Other suitable Rhein Chemie products used for peroxide vulcanization are Rhenofit® TAC and Rhenofit® TRIM. They are employed as activators, leading to partly increased hardness, higher moduli, outstanding resilience and good abrasion resistance of the vulcanizates. To improve the processing safety and aging properties of fluorocarbon elastomers (FKM), Rhein Chemie offers Rhenofit® D/A. With Rhenofit® CF, a crosslinking activator particularly used for FKM, an optimal compression set can be achieved at higher temperatures. Aflux® 54 decreases the viscosity of the rubber compounds and gives them excellent mold removal properties. Rhein Chemie has recently developed a system for curing acrylate rubbers (AEM and ACM). This system consists of the curing agent Rhenogran® HMDC-70/AEMD, the scorch retarder Rhenogran® ZDDT-50/AEMD (improves flow behavior and mold removal) and the accelerators Rhenogran® XLA-60 and Rhenogran® HPCA-50 (safer alternatives to DOTG). An outstanding contribution to the processing of AEM and ACM is provided by the processing promoter Aflux® 18, which significantly reduces the tackiness/stickiness of rubber compounds. Another special crosslinking system recommended for acrylate rubbers contains Rhenogran® Diuron-80/ACM and Rhenogran® NAST-50/ACM. A good balance between processing and physical properties can be achieved with this Diuron/alkali soap system. For the vulcanization of epichlorhydrin rubber (ECO), a curing system based on triazine has replaced the standard ETU curing system due to health and environmental considerations. The Rhein Chemie curing package recommended for this application comprises Rhenogran® TriazineTM-70/AEMD in combination with Rhenogran® HPCA-50. In addition to ETU/triazine-based curing systems employed for ECO/CO compounds, there are bisphenol curing systems where lead compounds are also used. Rhenogran® Na2CO3-70/CO F is an ideal substitute for lead derivatives that is used as an acid acceptor in these bisphenol curing systems. Aflux® 25 is a special processing aid developed for ECO rubber compounds. Its advantages are manifold and include good processing of the compounds, a noticeable reduction in the adherence of compounds to the mixing units, improved absorption of fillers, and the extrusion properties of the compounds.