Reinforcing biofiller "Lignin" for high performance green natural rubber nanocompositesElectronic supplementary information (ESI) available: The videos of three-dimensional LSCM images for NR-L40-S-soft and NR-L40-S-mill samples. See DOI: 10.1039/c6ra26359c

High performance eco-friendly natural rubber biocomposites filled with 5, 10, 20, and 40 parts per one hundred rubber by weight (phr) of lignin were prepared from sodium lignosulfonate and natural rubber (NR) latex using the soft processing method. The formation of network-like lignin structures was detected around the rubber phases even when the amount of lignin was increased to 40 phr. The Payne effect clearly suggested the presence of filler-filler interaction of lignin in the biocomposites. The distinguishably superior reinforcement effects of lignin at different levels of content were clearly apparent in the biocomposites. Specifically, the tensile stresses of the biocomposites significantly increased with an increase in the lignin content. Under dynamic conditions, the biocomposites showed larger storage moduli and lower dissipative loss with low glass transition temperatures with increasing amount of lignin. The generation of crystallites by strain-induced crystallization (SIC) was evaluated by using quick time-resolved wide-angle X-ray diffraction/tensile measurements, and a stepwise SIC phenomenon was observed for the lignin-filled NR soft biocomposites. This is a first report on the organic filler filled NR nanocomposite. The lignin content did not significantly affect the generation of crystallites of the NR biocomposites. This characteristic could strongly influence the development of rubber science and technology. Sodium lignosulfonate will be applicable as a good reinforcing biofiller for the preparation of green NR nanocomposites. High performance eco-friendly natural rubber biocomposites with various contents up to 40 parts per one hundred rubber by weight of lignin were successfully prepared from sodium lignosulfonate and natural rubber latex using the soft process.