ABSTRACT
The mechanical strength of natural rubber (NR) was enhanced by incorporating novel titanium carbide (TiC) nanocrystals as a filling material. The rubber nanocomposites were prepared through mixing TiC nanoparticles with NR latex and the resulting NR/TiC masterbatch was further mixed at the solid stage with other chemicals via internal mixing. The final rubber composites prepared using TiC as the nanofiller were denoted as NR/TiC-0, NR/TiC-0.5, NR/TiC-1.0, NR/TiC-2.5, and NR/TiC-5.0; moreover, a comparative study was conducted using carbon black (CB-330) as the filler and the composites were denoted as NR/CB-1.0 and NR/CB-5.0. As per the results of tensile tests, the NR/TiC-1.0 composite revealed the highest tensile value of 31.13 MPa and this indicated improvement by 92% compared to that of the control (NR/TiC-0 (16.22 MPa)); moreover, it indicated improvements by 73% and 63% compared to the values of NR/CB-1.0 and NR/CB-5.0, respectively. Moreover, scanning electron microscopy (SEM) analysis revealed a better dispersion of the NR/TiC-1.0 composite compared to the other composites. Furthermore, dynamic mechanical analysis (DMA) was conducted to observe the energy storage and loss properties at dynamic conditions; the results revealed that the highest storage peak and lowest loss peak were observed for the NR/TiC-1.0 composite. Also, thermogravimetric analysis revealed the superior thermal stability of the NR/TiC-1.0 composite to that of the others at the NR degradation temperature of around 400 °C. Importantly, the curing time (t 90) of NR/TiC-1.0 was reduced considerably compared to that of the other composites even the NR/CB composites, which would be beneficial for industries to save energy at the curing stages of tire-like applications. The improvements were significant when compared to the industrially well-known NR/CB composites and well above the industrially required minimum parameters of the tire industry. Ultimately, this will open up a distinct avenue for natural rubber reinforcement.
ABSTRACT
Thermal conductivity of natural rubber (NR) was enhanced by incorporating novel conductive hybrid nanofillers, namely polyaniline grafted carbon black (PANI/CB) nanoparticles and carbon black nanoparticles linked with carbon microfiber (CF/CB) composites. The PANI/CB hybrid fillers were synthesized using an in situ method, where aniline monomers were initially adsorbed onto carbon black spherical domains and, afterwards, it was polymerized in the presence of an oxidizer. Final rubber composites were prepared through melt mixing, where PANI/CB and CF/CB filler loading was kept at 40 parts per hundred of rubber (phr). The thermal conductivity values of the rubber composites with CF/CB (20 : 20) and PANI/CB (20 : 20) yield were 0.45 W m-1 K-1 and 0.31 W m-1 K-1, respectively and the thermal conductivity improved significantly compared to the control (0.25 W m-1 K-1) sample. The higher thermal conductivity values of CF/CB and PANI/CB incorporated composites suggest that the generated networked structure of CF and PANI nanofibers with CB nanoparticles has immensely contributed to enhancing the heat dissipation compared to that of the neat CB rubber composite. Scanning electron micrographs (SEM) confirmed the attachment of the synthesized PANI onto the spherical CB nanoparticles and interconnected morphology of CF/CB and PANI/CB hybrid fillers. The synthesized PANI/CB hybrid filler was further characterized using Fourier-transform infrared (FTIR) spectroscopy to evaluate the chemical properties. Furthermore, thermogravimetric analysis revealed the higher thermal stability of CF/CB (20 : 20) and PANI/CB (20 : 20) composites compared to the control. Moreover, the addition of CF/CB (20 : 20) and PANI/CB (20 : 20) improved the mechanical properties such as ultimate tensile strength, modulus at break, resilience and abrasion resistance significantly and well above the minimum required standard mechanical parameters in the tyre industry. These reinforced composites show great potential to be used as heat dissipating rubber composites in the tyre industry.
ABSTRACT
A novel hydroxyapatite montmorillonite (HAP-MMT) nanocomposite system was synthesized using a simple wet chemical in situ precipitation method. Neat nano hydroxyapatite (HAP) was also synthesized for comparison. The characterization of the materials was carried out using Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) isotherms to study the functional groups, morphology, crystallinity and the surface area respectively. Batch adsorption studies and kinetic studies on fluoride adsorption were conducted for the HAP-MMT system and for neat HAP. The effect of parameters such as contact time, pH, initial concentration, temperature, and thermodynamic parameters and the effect of coexisting ions on fluoride adsorption by HAP-MMT were studied. Results of the isotherm experiments were fitted to four adsorption isotherm models namely Langmuir, Freundlich, Temkin and Dubinin Radushkevich. Fluoride adsorption over HAP-MMT fitted to the Freundlich adsorption isotherm model and showed more than two-fold improved adsorption capacity (16.7 mg g-1) compared to neat HAP. The best-fitting kinetic model for both adsorbents was found to be pseudo second order. Calculated thermodynamic parameters indicated that the fluoride adsorption by HAP-MMT is more favorable compared to that on HAP within the temperature range of 27 °C-60 °C. Improved fluoride adsorption by HAP-MMT is attributed to the exfoliated nature of HAP-MMT. Gravity filtration studies carried out using a 1.5 ppm fluoride solution, which is closer to the ground water fluoride concentrations of Chronic Kidney Disease of unknown etiology (CKDu) affected areas in Sri Lanka, resulted in a 1600 ml g-1 break through volume indicating the potential of HAP-MMT to be used in real applications.
