The Partial Replacement of Halloysite Nanotubes (HNTs) and Precipitated Silica by Recycled Poly(ethylene terephthalate) Powder on Cure Behavior, Tensile Properties and Morphology of Natural Rubber Composites

In this article, halloysite nanotubes (HNTs) and precipitated silica were replaced by recycled polyethylene terephthalate powder (R-PET) in natural rubber composites. Five different compositions of NR/HNTs/R-PET and NR/Silica/R-PET composites [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. Comparison of the curing behavior, tensile properties, and morphological characteristics of natural rubber composites was studied. The results indicated that the replacement of HNTs and silica by R-PET decreased the tensile strength, tensile modulus, and elongation at break of composites, but NR/Silica/R-PET composites showed the lower trend than that NR/HNTs/R-PET did. The negative effect of these properties could be explained by the decrement of crosslink density, R-PET is unable to be transferred the stress due to the weal rubber-fillers interactions, and the reducing of ductility of rubber matrix. The curing results revealed that, with replacement of HNTs and Silica by R-PET, the scorch time (ts(2)) and cure time (tc(90)) were decreased. Scanning electron microscopy investigation of tensile fracture surfaces confirmed that co-incorporation of NR/HNTs/R-PET would improve the dispersion of R-PET and enhanced the interactions between fillers and NR matrix rather than NR/Silica/R-PET composites.