Development of zero-waste package for asphalt from natural rubber / ethylene vinyl acetate copolymer thermoplastic vulcanizates

Abstract

Asphalt is normally delivered in liquid form which was heated all the time. It consumes more energy and need the special truck to deliver it. An alternative way to deliver the asphalt in form of solid covered with package can reduce energy consumption and normal truck can be used to deliver. The objective of this research was to develop the zero-waste package for asphalt that was no waste after use and not harmful to asphalt properties. The research consists of two parts which are (1) development of package from natural rubber (NR) and ethylene vinyl acetate copolymer (EVA) thermoplastic vulcanizates (TPV), and (2) Test of asphalt package prepared from the TPV and studied on asphalt modification by incorporating TPV with various degree of crosslink. For the first part, the mixing method consists of two steps: dynamic vulcanization (DV) and further blending (FB). The weight ratio of EVA/NR was fixed at 50/50 wt/wt. Dicumyl peroxide (DCP) was used as a crosslinking agent and was fixed at 2 phr. Thermal stabilizers (TS) were fixed at 1 phr. Three mixing methods were compared: NR-DV which NR was only DV and then FB with EVA and thermal stabilizers (TS), Split-DV which NR and some EVA were DV and then FB with the rest of EVA and TS, and All-DV which NR and EVA was DV and then FB with TS. It was found that mixing method affected properties of TPV. NR-DV sample showed a heterogeneous texture because there was only crosslinked NR, this sample cannot be used. Mechanical properties of All-DV sample were inferior to those of Split-DV sample because of self-crosslinked EVA. The Split-DV method was selected to prepare the polymer modified asphalt (PMA). The TPV with different degree of crosslink were prepared by varying the DCP content from 0 to 1.5 phr. The TPV content was fixed at 5 wt%. It was found that the degree of crosslink affected the properties of PMA. The more degree of crosslink of TPV improved the physical properties of PMA with less viscosity when compared with the asphalt modified with non-crosslink TPV. It might be due to the long-chain polymer contained in non-crosslink TPV which has more entanglement of chain than the short-chain polymer or crosslinked rubber particles.