Effects of partial replacement of commercial fillers by recycled poly(ethylene terephthalate) powder on the properties of natural rubber composites

Commercial fillers, including carbon black (N550), halloysite nanotubes (HNTs), and precipitated silica, were replaced by recycled poly(ethylene terephthalate) powder (R-PET) in natural rubber (NR) composites. Five different compositions of NR/N550/R-PET, NR/HNTs/R-PET, and NR/silica/R-PET compounds, i.e., 100/20/0, 100/15/5, 100/10/10, 100/5/15, and 100/0/20 parts per hundred rubber (phr), were prepared on a two-roll mill. The curing behavior, tensile properties, and morphological characteristics of the natural rubber composites were investigated. The results indicated that the replacement of carbon black, HNTs, and silica by R-PET decreased the tensile strength and tensile modulus, such that NR/silica/R-PET composites showed the lowest effect, followed by NR/HNTs/R-PET and NR/N550/R-PET composites. The negative effect on these properties can be explained by the decrease of crosslink density. The curing results revealed that with the replacement of carbon black by R-PET, the scorch time and cure time decreased, but that the NR/HNTs/R-PET and NR/silica/R-PET composites exhibited the opposite trend. Scanning electron microscopy investigation of tensile fracture surfaces confirmed that the co-incorporation of N550/R-PET improved the dispersion of R-PET and enhanced the interaction between the fillers and NR matrix more than R-PET and silica/R-PET hybrid fillers. J. VINYL ADDIT. TECHNOL., 2012. (C) 2012 Society of Plastics Engineers