Marking of automotive rubber parts for recycling.

There are currently in the U.S. some 11 million vehicles retired from service each year. Many of these are scrapped and parts recycled from them. A great deal of the steel, aluminum copper, zinc and glass is recycled. These are easy to identify in the dismantling process. The tires are also fairly easy to identify and are either burned, ground or stockpiled. The composition of the tires is for the most part SBR, NR, PBD, small quantities of EPDM and butyl rubber. However, there are several hundred other rubber components used in the construction of the vehicle. These include hoses, belts, bushings, o-rings, wire harnesses, accelerator and brake pedals, weatherstripping, trunk and deck seals and numerous other components. The elastomers used in these non-tire components include polychloroprene, EPDM, nitrile, acrylic, fluoroelastomers, Hypalon, CPE, silicone, HNBR and a few others. Different vehicle manufacturers may use different elastomeric components for die same function. As a result, it is not possible to know the composition of a specific part without a chemical analysis of the part. It is expected that recycling will become more of an issue in the future. A method of marking rubber parts is needed now, so that in eight to ten years as current vehicles are removed from service, it will be possible to sort die rubber and thermoplastic elastomer vehicle components. Robert Coffey, marketing director of Prolerized Schiabo Neu Company (PSN) of Jersey City, NJ commented "that a system for practically identifying the composition of rubber parts removed in the dismantling process would be very helpful." PSN is the largest automobile recycler in America.

Recycling

The issue of vehicle recycling and making efficient use of recycled components has become an economic, environmental and legislative issue in recent years. As a result, the concept of vehicle dismantling has become an important approach to die problem of efficient used vehicle disposal. One of the problems facing vehicle dismantlers is being able to identify the composition of the elastomeric components recovered from scrapped vehicles. Without any identification for polymer rM one can only make an educated guess as to the rubber used in the manufacture of an automotive rubber component. To overcome this problem a system for marking automotive parts has been proposed and is being drafted by the SAE Committee for Automotive Rubber Parts, better known as CARS. The document has been titled Marking of Rubber Parts. The plastic industry already has a document in place and being used, entitled Marking of Plastic Parts. It is SAE J1344.

The creation of SAE J 1 344 Recommended Practice for the Marking of Plastic Parts in 1980 paved the way for the proper identification of these materials for recycling. It is a document that has evolved with the changing needs of the recycling industry. The issues and experiences of the rubber industry's efforts to establish their nomenclature protocol standard parallels those encountered by the plastic industry.

A key issue facing the rubber effort is the amount of identification detail necessary to properly direct die parts at the end of their useful life. Those involved in the marking of plastics recall that the initial document had only minor references to die filler content. Similarly, the rubber marking subcommittee is listening to the rubber recycling industry representatives on the issue of how much information is needed given the lettering size restrictions and sensitivity of part manufacturers to releasing content details. Obviously, a detailed identification can only be applied to parts with sufficient surface area to handle the notation.

The marking subcommittee will have a recommended practice ready for ballot in 1996. Like the plastic document, identification criteria will be simple and consistent with the current needs of the industry. When the committee is ready and the need established, the issue over identification and details for smaller parts like o-rings will be addressed.

Proposed system

All thermoset automotive rubber parts would be identified for their polymer composition. The system under consideration would use the ASTM D1418 nomenclature, where two to four capital letters are used to identify the polymer. In many cases these are widely accepted acronyms for the rubber. For example, natural rubber is NR and nitrile rubber is NBR.

The standard marking symbol will be 3 mm high and placed in a location that will not interfere with the performance of the component. If a part is too small for a 3 mm letter then smaller letters are recommended rather than no lettering. In the case of blends, the components will be shown. Figures 1-4 show samples of how the lettering would look. These are taken directly from the proposed document.