Gas transport through nano and micro composites of natural rubber (NR) and their blends with carboxylated styrene butadiene rubber (XSBR) latex membranes

From Nanoscale to Macroscale Characterization of Sulfur-Modified Oxidized Carbon Nanotubes in Styrene Butadiene Rubber Compounds

The homogeneous dispersion of carbon nanotubes (CNTs) in a rubber matrix is a key factor limiting their amazing potential. CNTs tend to agglomerate into bundles due to van der Waals interactions. To overcome this limitation, CNTs have been surface-modified with oxygen-bearing groups and sulfur. Using atomic force microscopy (AFM) techniques, a deep nanoscale characterization of the morphology, the degree of dispersion of the CNTs in the styrene butadiene rubber (SBR) matrix, and the thickness of the interfacial layer was carried out in this study. In this context, the results from nanoscale characterization showed that the thermal oxidation-sulfur treatment leads to a composite with better dispersion in the matrix, as well as a thicker interfacial layer, indicating a stronger filler-rubber interaction. The second part of this work focused on the macroscale results, such as the Payne effect, vulcanization curves, and mechanical properties. The Payne effect, vulcanization curves, and mechanical properties confirmed the lower reinforcing effect observed in the case of the chemical oxidation treatment because, on the one hand, this composite showed the highest agglomeration of CNTs after the acid treatment. On the other hand, the presence of acid residues provoked the absorption of basic accelerators on the surface of the CNTs.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Effect of Al2O3 on Nanostructure and Ion Transport Properties of PVA/PEG/SSA Polymer Electrolyte Membrane

Polymer electrolyte membrane (PEM) fuel cells have the potential to reduce our energy consumption, pollutant emissions, and dependence on fossil fuels. To achieve a wide range of commercial PEMs, many efforts have been made to create novel polymer-based materials that can transport protons under anhydrous conditions. In this study, cross-linked poly(vinyl) alcohol (PVA)/poly(ethylene) glycol (PEG) membranes with varying alumina (Al₂O₃) content were synthesized using the solvent solution method. Wide-angle X-ray diffraction (XRD), water uptake, ion exchange capacity (IEC), and proton conductivity were then used to characterize the membranes. XRD results showed that the concentration of Al₂O₃ affected the degree of crystallinity of the membranes, with 0.7 wt.% Al₂O₃ providing the lowest crystallinity. Water uptake was discovered to be dependent not only on the Al₂O₃ group concentration (SSA content) but also on SSA, which influenced the hole volume size in the membranes. The ionic conductivity measurements provided that the samples were increased by SSA to a high value (0.13 S/m) at 0.7 wt.% Al₂O₃. Furthermore, the ionic conductivity of polymers devoid of SSA tended to increase as the Al₂O₃ concentration increased. The positron annihilation lifetimes revealed that as the Al₂O₃ concentration increased, the hole volume content of the polymer without SSA also increased. However, it was densified with SSA for the membrane. According to the findings of the study, PVA/PEG/SSA/0.7 wt.% Al₂O₃ might be employed as a PEM with high proton conductivity for fuel cell applications.

Use of carbon and aluminosilicate nanofillers in XNBR composites designed for protective materials against oils

The objective of the work was to investigate the possibility of application of carbon and bentonite nanoparticles in carboxylated acrylonitrile-butadiene rubber (XNBR) and the related effects of the nanofillers on the structure, as well as mechanical and barrier properties, of the resulting composites. The composites were designed for use in protective clothing and gloves. XNBR compounds were modified with 2 phr of graphene flakes, graphene oxide, or modified bentonite, and crosslinked with sulfur-accelerator system. Rubber compounds were prepared using a conventional method with a laboratory rolling mill. The composites were studied in terms of structure (WAXS), surface morphology (AFM), the presence of functional groups (ATR-FTIR) barrier properties against chemical substances (mineral oil) and swelling properties, as well as mechanical properties (abrasion resistance and tensile strength). The composites were characterized by very high resistance to oil permeation (breakthrough time >480 min). The type of nanofiller added to the XNBR blend in the amount of 2 phr did not significantly affect mechanical parameters.

Polymer Nanocomposite Membranes

Based on the results of research works reflected in the scientific literature, the main examples, methods and approaches to the development of polymer inorganic nanocomposite materials for target membranes are considered. The focus is on membranes for critical technologies with improved mechanical, thermal properties that have the necessary capabilities to solve the problems of a selective pervaporation. For the purpose of directional changes in the parameters of membranes, effects on their properties of the type, amount and conditions of nanoparticle incorporation into the polymer matrix were analyzed. An influence of nanoparticles on the structural and morphological characteristics of the nanocomposite film is considered, as well as possibilities of forming transport channels for separated liquids are analyzed. Particular attention is paid to a correlation of nanocomposite structure-transport properties of membranes, whose separation characteristics are usually considered within the framework of the diffusion-sorption mechanism.

Molecular dynamics simulation on the mechanical properties of natural-rubber-graft-rigid-polymer/rigid-polymer systems

Explanation of the experimental phenomenon of modified natural-rubber using a MD method.

S, Zachariah AK, V. VK, M. A. S, Bose S, Souza FG, Thomas S. Percolated network formation in biocidal 3D porous PCL/clay nanocomposite scaffolds: effect of organic modifier on interfacial and water sorption properties

The influence of chemical interaction between poly(ε-caprolactone) (PCL) and Cloisite 10A on rheology, water permeability and antibacterial properties were subjected to detailed investigation.

Latex micro-balloon pumping in centrifugal microfluidic platforms

Centrifugal microfluidic platforms have emerged as point-of-care diagnostic tools. However, the unidirectional nature of the centrifugal force limits the available space for multi-step processes on a single microfluidic disc. To overcome this limitation, a passive pneumatic pumping method actuated at high rotational speeds has been previously proposed to pump liquid against the centrifugal force. In this paper, a novel micro-balloon pumping method that relies on elastic energy stored in a latex membrane is introduced. It operates at low rotational speeds and pumps a larger volume of liquid towards the centre of the disc. Two different micro-balloon pumping mechanisms have been designed to study the pump performance at a range of rotational frequencies from 0 to 1500 rpm. The behaviour of the micro-balloon pump on the centrifugal microfluidic platforms has been theoretically analysed and compared with the experimental data. The experimental data show that the developed pumping method dramatically decreases the required rotational speed to pump liquid compared to the previously developed pneumatic pumping methods. It also shows that within a range of rotational speed, a desirable volume of liquid can be stored and pumped by adjusting the size of the micro-balloon.

IMPROVEMENT IN PHYSICAL AND MECHANICAL PROPERTIES OF IIR/CR RUBBER BLEND ORGANOCLAY NANOCOMPOSITES

The effects of organoclay loading and chloroprene rubber (CR) concentration on the cure characteristics, microstructure, and mechanical and rheological properties of isobutylene–isoprene rubber (IIR)/CR blend were investigated. Different compositions of CR (10, 20, and 40 wt%) with Cloisite15A as organo modified nanoclay (1, 3, 5, and 7 wt%) were used for blends by a two-roll mill. Samples were vulcanized at 175 °C using a hot press. The cure and scorch times and also the maximum torque of the composites increased with the incorporation of organoclay. Mechanical properties such as tensile strength, elongation at break, modulus (100%, 200%, and 300%), and resilience improved with increasing nanoclay loading. The structure of the nanocomposites was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD results of nanocomposites indicated that the intercalation of polymer chains into the clay gallery was deduced from increasing the interlayer distance of silicate layers. TEM and SEM also directly confirmed XRD results.

Viscoelastic behavior and reinforcement mechanism in rubber nanocomposites in the vicinity of spherical nanoparticles

The viscoelastic behavior and reinforcement mechanism of nano ZnO reinforced natural rubber (NR) nanocomposites were investigated in this study. Dynamic mechanical analysis was performed to investigate the nature of the constrained polymer region in NR-nano ZnO nanocomposites, and the constrained polymer region is responsible for the reinforcement mechanism. The viscoelastic and tensile properties of NR nanocomposites were investigated with respect to the effect of nanofiller loading. All the nanocomposites showed a significant increase in storage modulus in the glassy and rubbery regions, the shift of the tan δ peak to the higher temperature region, and the lowering of the tan δ peak intensity compared to neat NR. The enhancement in the modulus is related to the weight % of the added nano ZnO as well as the volume of the constrained rubber chains in the proximity of ZnO nanoparticles. The study of the constrained volume of the polymer indicates that the structure of the nanocomposite possesses a moderately strong interfacial interaction between rubber chains and ZnO nanoparticles. The type of rubber-nanofiller interaction strongly influences the amount and modulus of the constrained region and contributes to the enhancement in the storage modulus of the resulting nanocomposites. The volume fraction of the constrained region of the NR nanocomposites was found to have good linear correlation with the weight % of nano ZnO. It was also understood that there should exist an optimum cross-linking density for a certain nanofiller reinforced rubber system, as well as partial physical adsorption of macromolecular rubber chains on the nanofiller surface. An optimum nanofiller loading is necessary for moderately strong rubber-nanofiller interaction and hence for the enhancement in the mechanical properties of the NR nanocomposites. A core-shell morphology model and constrained polymer model have been proposed to explain the constrained polymer chains in the NR-nano ZnO nanocomposite system on the basis of these results.