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Electrically conductive epoxidized natural rubber filled with conductive carbon black was prepared. The AC conductivity ( σAC), dielectric constant ( ɛ′), loss factor (tan δ*) and dynamic mechanical properties of the composites were studied. It was found that the epoxide groups in epoxidized natural rubber molecules positively contributed to AC conductivity, dielectric constant, and tan δ* of the composites. Especially, the composite with epoxidized natural rubber containing 50% mol epoxide (epoxidized natural rubber–50) showed better electrical and dynamic mechanical properties than the composites with epoxidized natural rubber–25 or NR. The effects of conductive carbon black loading level on electrical conductivity and dielectric constant of the epoxidized natural rubber–50/conductive carbon black composites was also studied. The percolation threshold was found at very low content of conductive carbon black at volume fraction of 0.07 with the critical exponent value 2.04. Furthermore, the glass transition temperatures of epoxidized natural rubber–50/conductive carbon black composites were higher than those of epoxidized natural rubber–25/conductive carbon black or NR/conductive carbon black composites, and increased with conductive carbon black content.

The influence of multi‐walled carbon nanotubes (MWCNTs) and conductive carbon black (CCB) on cure, electrical, dielectric, and mechanical properties of epoxidized natural rubber (ENR) composites was investigated. It was found that short MWCNTs (S‐MWCNTs) with low loading significantly affected the cure characteristics in a way similar to high loading of CCB. Moreover, the ENR/S‐MWCNTs composites exhibited high AC conductivity, dielectric constant, and dielectric loss tangent (tan δ) compared to the ENR/CCB and ENR/L‐MWCNTs (long MWCNTs) composites. In addition, the S‐MWCNTs composites showed the lowest percolation threshold concentration, defined as the lowest loading to form conductive paths in the insulating ENR matrix. This might be attributed to the comparatively high interfacial polarization, with good dispersion and distribution, of the S‐MWCNTs in ENR matrix. These characteristics were confirmed by TEM imaging and by a high bound rubber content, corroborating strong filler–rubber interactions in the ENR/S‐MWCNTs composites. However, the L‐MWCNTs composites showed the lowest electrical and other related properties, despite the highest aspect ratio and specific surface area of this filler. This might be because of the flocculation of nanotubes by mutual entanglement, leading to a poor uneven distribution in the ENR matrix. POLYM. COMPOS., 38:1031–1042, 2017. © 2015 Society of Plastics Engineers

Electrical and mechanical properties of epoxidized natural rubber (ENR-25) filled with conductive carbon black (CCB) have been investigated. SEM was used to analyze dispersion of CCB particles in rubber matrix. The results indicated that the AC conductivity increase with increasing volume fraction of carbon black as well as frequency. The percolation thresholds of the electrical conductivity was found at 0.10 volume fraction of CCB. Furthermore, addition of CCB at volume fraction 0.05 caused the highest tensile strength of the composites. The tensile strength and elongation at break were decreased with increasing content of CCB greater than 0.05 volume fraction. However, the volume fraction of CCB at 0.10 demonstrated the most suitable proportion for the ENR composites with superior electrical and mechanical properties.

Conductive thermoplastic vulcanizates based on epoxidized natural rubber (ENR) and copolyamide (COPA) blends were prepared using two alternative mixing stages to incorporate MWCNTs: after or before dynamic vulcanization (i.e., ADV or BDV, respectively). Effects of ionic liquid (IL) loading on properties of the blends were also studied. The results indicated that both ADV and BDV mixing preferentially localized MWCNTs in the COPA phase. However, with BDV mixing some of the MWCNTs also resided in ENR domains. The TPVs made with BDV showed higher electrical conductivity, dielectric properties, and superior stress relaxation behavior relative to those prepared by ADV. This might be due to better dispersion of MWCNTs in both phases of the blends. In addition, the electrical and dielectric properties were improved by the IL in a dose dependent manner with the IL loading. However, the IL reduced stress relaxation of the TPVs due to its plasticizing effect.

This article deals with the kinetic of thermal degradation and thermal stability of natural rubber (NR) filled with titanium dioxide (TiO2) nanoparticles. Incorporation of TiO2 nanoparticles was done through a latex mixing method. This is to ensure the homogeneity of TiO2 nanoparticles throughout the NR matrix. Adding TiO2 nanoparticles results in shifting the decomposition temperature and char residue irrespective of the loadings of TiO2 nanoparticles. This is confirmed by the calculated kinetic parameters of the composites, indicating that higher energy is required to decompose the NR chains. Based on this analysis, a schematic model for thermal stability of TiO2 nanoparticles filled NR composites is proposed. POLYM. COMPOS., 40:3149–3155, 2019. © 2018 Society of Plastics Engineers

Reclaimed rubber (RR) from waste tires was introduced as a wood adhesive by blending with epoxidized natural rubber (ENR). To improve the polarity of RR and compatibility with ENR, maleic anhydride (MA) was grafted onto RR chains. Influences of RR and RR-g-MA (maleic anhydride grafted reclaimed rubber) on the adhesion of wood adhesive along with their properties such as crosslinking, mechanical properties, thermal stability, and wettability were studied. It was found that RR and RR-g-MA affect the vulcanization of ENR by increasing crosslink density. Especially, in the case of using RR-g-MA generates a new form of an ester linkage. The higher crosslink density together with the formation of ester linkages results in superior thermal stability by the addition of RR-g-MA. In addition, the incorporation of RR exhibited an increase in the lap shear strength when compared with the pure ENR. This improvement is due to the increased crosslink density because the presence of RR resulted in the enhanced cohesive strength of rubber adhesive. Additionally, the incorporation of RR-g-MA showed higher efficiency to improve the adhesion of rubber adhesive. The addition of RR-g-MA has not only enhanced the cohesive strength of rubber adhesive, but also increased the adhesive strength from the interaction between the hydroxy group in cellulose on the wood surface and the polar functional group (i.e., oxirane rings of ENR, maleic group of RR-g-MA and ester group of ester linkage) of rubber adhesive. Therefore, the cohesive fracture was observed in ENR/RR-g-MA adhesive. HIGHLIGHTS The worn-out rubber tire as a mass waste can be utilized to develop effective adhesives The addition of maleic anhydride grafted reclaimed rubber caused to generate new ester linkage between epoxidized natural rubber chains The epoxidized natural rubber vulcanizates with maleic anhydride grafted reclaimed rubber showed superior thermal stability The addition of maleic anhydride grafted reclaimed rubber enhanced the adhesive strength of rubber adhesive from the interaction between hydroxy group in cellulose on the wood surface and the polar functional group of rubber adhesive GRAPHICAL ABSTRACT

The objective of this research was to investigate the effect of magnesium hydroxide on the flame retardant properties of adhesive materials. The amount of magnesium hydroxide was varied from 2.5 to 10 phr. The adhesive preparation was performed by means of an aqueous filler dispersion technique. The dispersion of magnesium hydroxide in adhesive was observed by SEM images. The mechanical property of the adhesive joint was conducted by shear stress according to the ASTM D1002 standard. The flame retardant property of adhesives was measured in the horizontal burning testing method. The results revealed that the magnesium hydroxide formed agglomeration. For mechanical test, incorporation of magnesium hydroxide caused a cohesive failure in the substrate. The amount of magnesium hydroxide at 7.5 phr. possessed a maximum adhesive shear stress of 1,140 N. This was due to the magnesium hydroxide acting as reinforcing filler. The flame retardant properties of magnesium hydroxide increased with increasing magnesium hydroxide content. However, only adhesive with 10 phr was lower than 75 mm/min. The results can finally be concluded that the incorporated of magnesium hydroxide at 10.0 phr. remarkable improved the flame retardant properties of adhesive materials.