Softwood-lignin/natural rubber composites containing novel plasticizing agent: Preparation and characterization

Composite materials based on natural rubber were obtained by using glycerolysate (decomposition product of polyurethane) as a novel plasticizer. In order to determine the effect of various lignin content, four different filler amounts were used, namely, 5 phr (parts per 100 parts of natural rubber) of lignin (WLI5G), 10 phr (WLI10G), 20 phr (WLI20G), and 40 phr (WLI40G). The reference specimen without lignin (WLI0G) was also prepared. The resulting vulcanizates were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) to determine the chemical interaction between the lignin powder and the natural rubber chain. Scanning Electron Microscopy (SEM) of the cross-sections of the obtained materials was carried out to determine the adhesion between lignin and rubber. The results of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) showed that the samples containing 5 and 10 phr of lignin had the best thermal properties. Also, the measured mechanical properties confirmed these findings.