Recycling of EPDM Rubber : Utilization of Factory Waste as Filler in Virgin EPDM
Ceni Jacob, A.K.Bhowmick, S.K.De, Prajna P. De
Rubber Tech. Center, Indian Inst. of Techn.,   India

The processability, curing characteristics and mechanical properties of raw EPDM (R-EPDM) compound filled with powdered waste EPDM vulcanizate (W-EPDM) were studied. A mechanical grinder with silicon carbide abrasive wheel rotating at 2950 rpm was used for the preparation of powdered rubber. SEM studies of the powder reveal that the W-EPDM particles exist in chain-like aggregates. The Mooney viscosity of the compounds increases drastically with the W-EPDM content due to the highly aggregated structure of the powdered rubber. The Mooney scorch time decreases upto 200 phr of W-EPDM beyond which it slightly increases. Rheometric studies show that the extent of crosslinking as well as the cure rate decreases with W-EPDM loading. The variation in the cure behavior of the waste rubber powder filled compounds is believed to be due to the opposing effects of accelerator migration from W-EPDM to R-EPDM tending to reduce the scorch time and sulfur migration from R-EPDM to W-EPDM tending to increase the scorch time by reducing the rate of curing. Processability studies using Monsanto Processability Tester in a shear rate range of 306 s-1 to 1533 s-1 show that the addition of W-EPDM results in decreased die swell and lesser distortion of the extrudates. Results of mechanical property measurements reveal that the carbon black filled fine W-EPDM particles reinforce the matrix keeping the low-strain modulus and hardness constant. The counterbalancing effects of increasing carbon black content and decreasing crosslink density of the matrix with increasing W-EPDM loading may be the reason for the variation in mechanical properties of the W-EPDM powder-filled EPDM vulcanizates.

Session: MO-4

Symposia: 13

Time: 17h00