Characterization of Natural Rubber Latex/Chitosan Blends

The Modification of Activated Carbon for the Performance Enhancement of a Natural-Rubber-Based Triboelectric Nanogenerator

Increasing energy demands and growing environmental concerns regarding the consumption of fossil fuels are important motivations for the development of clean and sustainable energy sources. A triboelectric nanogenerator (TENG) is a promising energy technology that harnesses mechanical energy from the ambient environment by converting it into electrical energy. In this work, the enhancement of the energy conversion performance of a natural rubber (NR)-based TENG has been proposed by using modified activated carbon (AC). The effect of surface modification techniques, including acid treatments and plasma treatment for AC material on TENG performance, are investigated. The TENG fabricated from the NR incorporated with the modified AC using N2 plasma showed superior electrical output performance, which was attributed to the modification by N2 plasma introducing changes in the surface chemistry of AC, leading to the improved dielectric property of the NR-AC composite, which contributes to the enhanced triboelectric charge density. The highest power density of 2.65 mW/m2 was obtained from the NR-AC (N2 plasma-treated) TENG. This research provides a key insight into the modification of AC for the development of TENG with high energy conversion performance that could be useful for other future applications such as PM2.5 removal or CO2 capture.

Biodegradable and highly conductive polymeric blend based on the latex of Calotropis gigantea as solid electrolyte in energy storage applications

A blend polymer based on the latex of the South-Asian giant milkweed Calotropis gigantea (CGL) combined with poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) at a mass ratio of 1:1 without the addition of doping salts was synthesized via solution casting to prepare an ionic conductive film. The morphology, crystalline state, vibrational and thermal properties of the film were investigated by Scanning electron microscopy, X-ray diffraction, Fourier Transform infrared spectroscopy (FTIR), Thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The ionic conductivity and transport properties were investigated by using electrochemical impedance spectroscopy (EIS) Technique. Due the highest ionic conductivity at room temperature (2.7 x 10−2 S/cm), all-solid-state electrolyte was assembled using the prepared polymer film and a comparative study was conducted with respect to 1M H2SO4 liquid electrolyte, regarding the specific capacitance and the electrical properties. The results demonstrate that the fabricated all-solid-state supercapacitor using PVDF-HFP/CGL blend polymer film as electrolyte matches the performance of the liquid electrolyte.

Roles of Chitosan as Bio-Fillers in Radiation-Vulcanized Natural Rubber Latex and Hybrid Radiation and Peroxide-Vulcanized Natural Rubber Latex: Physical/Mechanical Properties under Thermal Aging and Biodegradability

Although natural rubber was regarded as biodegradable, the degradation is a time-consuming process that could take weeks or months for any degradation or substantial weight loss to be observable, resulting in the need for novel processes/methods to accelerate the rubber degradation. As a result, this work investigated the potential utilization of chitosan (CS) as a biodegradation enhancer for radiation-vulcanized natural rubber latex (R-VNRL) and hybrid radiation and peroxide-vulcanized natural rubber latex (RP-VNRL) composites, with varying CS contents (0, 2, 4, or 6 phr). The R-VNRL samples were prepared using 15 kGy gamma irradiation, while the RP-VNRL samples were prepared using a combination of 0.1 phr tert-butyl hydroperoxide (t-BHPO) and 10 kGy gamma irradiation. The properties investigated were biodegradability in the soil and the morphological, chemical, mechanical, and physical properties, both before and after undergoing thermal aging. The results indicated that the biodegradability of both the R-VNRL and RP-VNRL composites was enhanced with the addition of CS, as evidenced by increases in the percentage weight loss (% weight loss) after being buried in soil for 8 weeks from 6.5 ± 0.1% and 6.4 ± 0.1% in a pristine R-VNRL and RP-VNRL samples, respectively, to 10.5 ± 0.1% and 10.2 ± 0.1% in 6-pph CS/R-VNRL and 6-pph CS/RP-VNRL composites, respectively, indicating the biodegradation enhancement of approximately 60%. In addition, the results revealed that the addition of CS could increase the value of tensile modulus by 119%, while decrease the values of tensile strength and elongation at break by 50% and 43%, respectively, in the specimens containing 6-phr CS. In terms of the color appearances, the samples were lighter and yellower after the addition of CS, as evidenced by the noticeably increased L* and b* values, based on the CIE L*a*b* color space system. Furthermore, the investigation into the effects of thermal aging showed that the overall tensile properties for both curing systems were reduced, while varying degrees of color change were observed, with the pristine R-VNRL and RP-VNRL samples having more pronounced degradation/changes for both properties. In conclusion, the overall results suggested that CS had great potential to be applied as a bio-filler in R-VNRL and RP-VNRL composites to effectively promote the biodegradability, environmental friendliness, and resistance to thermal degradation of the composites.

The effective removal of phenol from aqueous solution via adsorption on CS/β-CD/CTA multicomponent adsorbent and its application for COD degradation of drilling wastewater

The 3-chloro-2 hydroxypropyltrimethyl ammonium chloride was successfully introduced into the β-cyclodextrin-modified chitosan to create the multicomponent adsorbent O-HTACC-g-CD. The structure of sorbent was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy. The adsorption capacity of O-HTACC-g-CD toward phenol was investigated as a function of pH, temperature, contact time as well as adsorbent dosage. The Box-Behnken response surface methodology was employed to optimize the effects of experimental parameters including adsorbent dose, pH, and time on the adsorption of phenol at 298.15 K. The obtained optimal values for adsorbent dose, pH, and time were 0.06 g, 6, and 200 min, respectively. The obtained experimental data follows the pseudo-second-order kinetic and Langmuir model. The thermodynamic parameters such as free energy change, enthalpy change, and entropy change were calculated, revealing that adsorption of phenol on O-HTACC-g-CD is a spontaneous and exothermic process. The prepared O-HTACC-g-CD displayed high adsorption capacity (39.98 mg g-1) and excellent removal rate (96%) for phenol from the aqueous solution at 288.15 K. The gained removal rates of chemical oxygen demand (CODCr) were in the range of 60.6-61.2%. Considerable results of sorption could be attributed to the multicomponent structure of the adsorbent with more active sites including the cavities, amino, and carboxyl functional groups which provided better sites for the phenolic pollutant to adsorb on the adsorbent via Van der Waals force, hydrogen bond, and the inclusion effect. Therefore, the results obtained strongly suggest that O-HTACC-g-CD could be an effective adsorbent for the removal of phenol and CODcr from drilling wastewater.

Chitosan and Natural Rubber Latex Biocomposite Prepared by Incorporating Negatively Charged Chitosan Dispersion

Generally, natural rubber/chitosan (NR/CT) biocomposites could be prepared by either mixing natural rubber latex (NRL) with CT acid solution or mixing dry NR with CT powder on mixing equipment. In the present work, a new mixing method has been proposed and properties of the obtained NR/CT biocomposites are investigated. CT particles were prepared to have a negative charge that could be dispersed in water by using a ball mill before mixing with NRL. The effects of CT loading varied from 0 to 8 phr on latex properties and physical properties of NR/CT biocomposite films were focused. The results showed that the viscosity of NRL increased with increasing CT loading. With increasing CT loading from 0 to 8 phr, 300% modulus of the NR/CT biocomposite film increased, whereas the opposite trend was found for elongation at break. Additionally, the presence of CT in the biocomposite resulted in an increased elastic modulus (E') in conjunction with enhanced antibacterial activity against Staphylococcus aureus (S. aureus).

The Effect of Chitosan Loading on the Properties of Chitosan Filled Epoxidized Natural Rubber Compounds

The study of chitosan loading onto epoxidized natural rubber compounds were prepared by incorporation of chitosan into epoxidised natural rubber matrix using a two-roll mill. The effects of chitosan loading on the curing characteristics, tensile properties and morphology of the compounds were investigated. Results indicated that slight changes in curing time (t90), and scorch time (tS2) of the compounds with the incorporation of chitosan. An increment is observed in the maximum torque, tensile modulus and durometer hardness of the compounds while tensile strength and elongation at break declines with chitosan loading.