By Liz White, ERJ staff
Mannheim, Germany- Rhein Chemie Rheinau GmbH is warning rubber processors-especially automotive fuel hose producers-that from July 1, 2005, it will â€¦ no longer be permissible to use compounds containing lead in elastomer components for passenger cars and commercial vehicles.â€
The European Directive on the disposal of end-of-life vehicles is quite clear on the elimination of lead, points out Rhein Chemie, adding that this also applies to manufacturers of technical rubber articles.
For lead-free curing systems, Rhein Chemie claims its polymer-bound sodium carbonate, Rhenogran Na2CO3-70/CO F is a valuable acid acceptor, avoiding the moisture content problems created with normal sodium carbonate which is hygroscopic.
Lead-free systems typically need a curing agent-such as a bisphenol derivative-a phosphonium derivative as activator and an acid acceptor.
Sodium carbonate, despite being a particularly suitable acid acceptor, is also hygroscopic,or moisture attracting, as is the total curing system, says Rhein Chemie. Since curing behaviour is affected by the system's moisture content-and the chemical also has a tendency to clump-the rubber must be specially protected to avoid scrap and quality problems, the firm said.
Rhein Chemie claims its polymer-bound sodium carbonate provides such protection. The product contains a particularly fine grade of sodium carbonate,â€ dispersed in a special epichlorohydrin binder (CO), which particularly effectively protects the acid acceptor from changes in moisture content.
Transitional regulations, have so far allowed rubber part makers to use lead compounds where, for technical reasons, such use was unavoidable, but these also lapsed from 1 July.
All the world's major car makers will require their suppliers to introduce lead-free automotive parts, the firm points out. .
At present, lead curing is primarily used in hose manufacture, in particular for fuel lines. These multi-ply speciality products often use combinations of fluororubber or fluorothermoplastics, ECO/CO compounds and, sometimes, also AEM and ACM compounds. In such cases, Rhenogran Na2CO3-70/CO F also enhances bonding between the fluoropolymers and the ECO/CO compound, Rhein Chemie said.