Abstract: Two types of lignins were obtained from alkaline pulping black liquors by acidulation using nitric acid and sulphuric acid, and their particle-size distributions were analyzed. A comparative investigation was conducted for the properties of ethylene-propylene-diene-monomer (EPDM) rubbers with the two types of lignins and silane-coupling agent. The results indicated that the two types of lignins exhitibted a smaller value of D50 and a bigger specific surface area. The incorporation of lignin-coupling agents improved the mechanical performances of EPDM rubber more significantly than the silane-coupling agent. The tensile strength, elongation at break and hardness of EPDM rubbers increased by 21.42 %, 22.55 % and 8 degree with the addition of 1.5 phr nitrate lignin (based 100 g rubber). The Fourier-transform infrared spectroscopy (FTIR) analysis and scanning electron microscopic (SEM) observation indicated that the lignins played a role in the reinforcement of EPDM rubber. Thermogravimetric analysis revealed that the lignins and silane-coupling agents improved the thermal stability of EPDM rubbers. The lignins could be used to replace the silane-coupling agent for modification of EPDM rubbers in a cost-effective way and therefore exhibited good application potential.

Key words: ethylene-propylene-diene-monomer rubber, lignins from pulping black liquor, silane coupling agent, characterization