Recycling of Cured Fluoroelastomer for Cost Control and Improved Performance
|Date Published||January 1, 2005|
Effective yield in some manufacturing plants producing thermoset rubber can be as low as 50%. Much of the waste stream is clean, cured or partially cured rubber generated by transfer and injector runners, flash trimmings, and defective parts. The very nature of the fluoroelastomer (FKM) curing system prohibits effective devulcanization. Traditionally these materials have been considered waste and are land filled. No efficient method of reusing it is widely accepted. FKM compounds are the most costly of all rubber materials used today. They can also be challenging to manufacture in some applications. This paper discusses a commercially available process owned by Rexhide Industries of Tyler, Texas that is designed exclusively to recycle cured fluoroelastomer (FKM) waste. The patented mechanical grinding process is capable of reducing cured or partially cured materials into particles consistently less than 100 microns or even smaller. Once processed into these powders the material can then be incorporated back into virgin polymer or into rubber compound with little or no adverse effects on the compound’s processing in the factory or performance in the application. This paper describes the cautions one should be aware of when attempting to recycle FKM. It will address the obstacles one may encounter using the materials and describes techniques to overcome these issues. SEM, EDX, FTIR and TGA methods are used to analyze the particulates generated by the process. The processing effects of the rubber compound are illustrated by mooney viscosity, rheology and RPA or Rubber Processing Analyzer and rubber flow index. Compound performance is characterized by testing the cured FKM compound through ASTM D-2000 M2HK A1-10 B38 EF31 EO78. Processing improvements as well as cost savings are available to rubber fabricators using materials from this process.