Waste rubber management through developing blends of thermoplastics with ground tire rubber (GTR) has gained significant attention for creating sustainable, high-performance materials with enhanced properties. In this work, we developed customized graphene/polymer nanocomposites applying GTR, ethylene-vinyl acetate copolymer (EVA), and graphene nanoplatelets (GNPs), taking carbon black (CB) as the reference additive. A wide range of electrical conductivity from 10^–12 S/cm (dielectric) to 10^–5 S/cm (semiconductor) was obtained for optimized composites containing GNPs and CB, respectively. Thermal, mechanical, and flame-retardant properties looked promising for additive manufacturing, while electrical conductivity was tailored for soft electronics. In view of processability, mechanical strength, and elasticity, GNPs-incorporated EVA/GTR composites showed an edge over their CB-aided counterparts. For example, tensile strength and elongation at break of EVA/GTR blends reinforced with 20 phr GNPs were 4.8 MPa and 681%, respectively, compared to 4.0 MPa and 651% for the composite comprising an identical amount of CB. Interestingly, combining GNPs and CB enhanced the thermal stability and flame retardancy of EVA/GTR compared to only GNPs or CB. These results were promising from both sustainability and advanced functional materials perspectives.

This work presented the synthesis of α-carboxyl, ω-hydroxyl natural rubber (CHNR) for use as an alternative toughening agent for poly(lactic acid) (PLA). The proton nuclear magnetic resonance spectroscopy (¹H-NMR) and Fourier transform infrared spectroscopy (FTIR) analyses verified the chemical structure of CHNR consisting of the hydroxyl and carboxyl end groups. The molecular weights of CHNR were set from 5000 to 15 000 g·mol^–1 which were determined by gel permeation chromatography (GPC) and ¹H-NMR. The PLA and CHNR were prepared by reactive blending using a twinscrew extruder. It was found that the reaction between PLA and CHNR proceeded through transesterification without a catalyst. The formation of copolymer (PLA-co-CHNR) at the interface of PLA and CHNR increased the interfacial adhesion between the two phases. Differential scanning calorimetry (DSC) analysis revealed that CHNR was more compatible with PLA than natural rubber (NR). The compatibilization affected the blend morphology by reducing the interfacial tension. It resulted in a reduction of rubber particle size. The CHNR with a molecular weight of 5000 g·mol^–1 showed the greatest improvement in the toughness and ductility of PLA.