Natural Rubber Matrices Research Articles

Ultra-Low Loading of Ultra-Small Fe3 O4 Nanoparticles on Nonmodified CNTs to Improve Green EMI Shielding Capability of Rubber Composites.

From a material design perspective, the incorporation of Fe3 O4 @carbon nanotube (Fe3 O4 @CNT) hybrids is an effective approach for reconciling the contradictions of high shielding and low reflection coefficients, enabling the fabrication of green shielding materials and reducing the secondary electromagnetic wave pollution. However, the installation of Fe3 O4 nanoparticles on nonmodified and nondestructive CNT walls remains a formidable challenge. Herein, a novel strategy for fabricating the above-mentioned Fe3 O4 @CNTs and subsequently assembling segregated Fe3 O4 @CNT networks in natural rubber (NR) matrices is proposed. The advanced and unique structure, magnetism, and lossless conductivity endow the as-obtained Fe3 O4 @CNT/NR with a shielding effectiveness (SE) of 63.8dB and a low reflection coefficient of 0.24, which indicates a prominent green-shielding capability that surpasses those of previously reported green-shielding materials. Moreover, the specific SE reaches 531dB cm-1 , exceeding that of those of previously reported carbon/polymer composites. Meanwhile, the outstanding conductivity enables the composite to reach a saturation temperature of ≈95°C at a driving voltage of 1.5V with long-term stability. Therefore, the as-fabricated Fe3 O4 @CNT/rubber composites represent an important development in green-shielding materials that are applied in cold environment.

An experimental investigation on the matrix dependent rheological properties of MRE

The rheological properties of magnetorheological elastomers are influenced by magnetically sensitive fillers and the elastomer matrix. The ability to respond to an external magnetic field is imparted by the fillers, while the load-bearing capability is determined by the matrix type. In this paper, the effect of matrix material on the properties of magnetorhological elastomer is explored experimentally. Carbonyl iron particle content is varied by 0%, 15% and 25% by volume to produce magnetorheological elastomer samples using natural rubber, silicone rubber and nitrile butadiene rubber matrices. Forced transmissibility test approach was employed to evaluate the field induced variations in the dynamic stiffness and loss factor of magnetorheological elastomers. The dynamic stiffness of nitrile butadiene rubber is the highest, while that of silicone rubber is the lowest. Addition of carbonyl iron particles significantly improves stiffness, although these gains depend on the properties of unfilled matrix. The addition of 25% by volume of carbonyl iron particle increased the dynamic stiffness of a silicone rubber matrix based magnetorheological elastomer by 67.78%, while the similar change in magnetorheological elastomer with nitrile butadiene rubber matrix was 38.58%. The field dependent response of magnetorheological elastomers is governed by the matrix and ferromagnetic filler concentration. These qualities are higher in magnetorheological elastomer with a low initial dynamic stiffness matrix and lower in magnetorheological elastomers with a stiffer matrix.

Transport of Small Molecules in Loaded Natural Rubber: Experimental Measurement and Numerical Simulation

Small organic molecules such as plasticizers, antioxidants, and some active molecules such as scent/fragrance compounds and drug molecules are incorporated into natural rubber materials to modify their properties and processability or utilize them as carriers in delivery systems. The transport of those small molecules within the rubber can greatly alter the properties and performances of the loaded rubber materials. Thus, it is important to study the transport properties of those molecules in natural rubber matrices and the factors influencing how fast the molecules diffuse. In this work, vulcanized rubber sheets with three different cross-link densities loaded with eight small molecules with different boiling points, molecular weights, and chemical moieties were prepared. Desorption experiments were performed to determine the mass transfer coefficients and diffusion coefficients of those molecules, and the corresponding numerical models were built. Good agreements between experiments and numerical simulation were observed. It was found that the mass transfer coefficients of those small molecules decreased with increasing boiling points but remained practically constant among rubber sheets with different cross-link densities. The diffusion coefficients of those small molecules did not show evident correlation with their molecular weights, but their relationships with cross-link densities indicated that for some molecules there might be an optimal cross-link density where a small molecule reached its maximum diffusion coefficient. The resulting findings could be applied to a wide range of fields.

Composites of thermoplastic starch/natural rubber blends for fertilizer-releasing in agriculture

Thermoplastic starch (TPS) based on the mixture of cassava starch and glycerol was prepared and blended with the natural rubber (NR) and epoxidized NR (ENR). The resulting blend was further filled with fertilizer grade 16–16–16. The effects of fertilizer concentration on the properties of the blends and the growthability of maize seedling were investigated and characterized. In case of the specific properties of the blends, it was found that the blends based on NR and ENR matrices exhibited a reduction in tensile properties upon increasing the fertilizer concentration, while the solubility, water absorption and biodegrability were improved. In particular, the blends of TPS/ENR with fertilizer showed better properties than that of the blend with NR due to the physical interaction of hydrogen bonding among the polymer molecules as confirmed from ATR-FTIR. Although both the blends were found to be decomposed within a period of two weeks, the releasing efficiencies significantly affected the growth of maize seedlings. According to the growthability based on count and greenness of leaves, shoot and root biomasses and phytotoxicity of fertilizers, the TPS/ENR with 80 phr of fertilizer represented the suitable one for growing the seedlings with proper release ability of fertilizer, especially the N, P and K elements during planting. Relating the water swelling of 180 %, it was found that the approximately 90 % of N, 70 % of P and 95 % of K were released before the complete decomposition degradation. This newly controlled release fertilizer (CRF) system can be applied for several plants by knowing the fertilizer concentration and ease of shape designing.

A comparative study on the interfacial characteristics and tensile behaviors of natural rubber composites reinforced by carbon and boron nitride nanotubes

AbstractThe reinforcing effect of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) on the interfacial characteristics and tensile behaviors of natural rubber (NR) composites were comparatively investigated using molecular dynamics simulations. A pull‐out simulation was performed to study the interfacial characteristics between CNTs, BNNTs and NR matrices. The results showed that increases of about 56.63% and 90.14% in the interfacial frictional force and interfacial shear strength were obtained for the composites by the incorporation of BNNTs than those by the incorporation of CNTs. A uniaxial tensile process was fulfilled by using the constant true strain rate method to study the mechanical properties of the NR composites reinforced by CNTs and BNNTs. The results indicated that significant increases of 22.34% and 26.59% in the Young's modulus, 4.34% and 19.28% in the yield stress, and 11.07% and 8.01% in the tensile strength were respectively achieved by the incorporation of CNTs and BNNTs as reinforcements. To deeply reveal the deformation mechanisms of the NR composites, the mean square displacement and root‐mean‐square radius of gyration of the NR chains, the fractional free volume in the NR composites, and the interfacial interaction energy were calculated and discussed accordingly.

Green biocomposites of chitosan dispersed in natural rubber matrices, and their urea controlled-release application

A green biocomposite comprising chitosan dispersed in partially cross-linked natural rubber matricesd was prepared. The starting materials and biocomposites were characterized by means of Fourier transform–infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Chitosan was found well dispersed in partially cross-linked natural rubber matrices indicating that natural rubber latex is successfully stabilized by sodium dodecyl sulfate. The swelling study of the biocomposites was carried out in several solvents. The biocomposites were used for the controlled-release of urea. The release behavior was found consistent, controlled, and prolonged over a period of 72 h. The Korsmeyer–Peppas model was applied to the experimental data and the possible release mechanism was found Fickian diffusion, which indicates that the polymer relaxation time is much greater than the characteristic solvent diffusion time.

Effect of Rosin Resin on the Properties of Natural Rubber/Polyester Layered Fibers

With the development of rubber technology the requirements for rubber products are becoming more and more strict. Enhancing the interfacial bonding strength between vulcanized natural rubber (NR) and polyester fibers (PEF) has become our research goal. In the research described here the effect of rosin resin (RR) on the properties of NR/PEF was studied. Dynamic experiments were conducted within the strain range from 1 to 100% using a rubber process analyzer (RPA). The adhesive properties of the RR in the NR matrices with the PEF were further studied by the peel test, which indicated an enhancement of the bonding effect in the vulcanized NR-PEF composites. The failure modes of the mixtures following various aging conditions were studied by scanning electron microscopy (SEM). When 3phr of RR were added to the NR/PEF composite, the interfacial bonding strength between the rubber and fiber had the best value compare to samples with 0, 1, 2, 4 and 5phr. Our results indicated that RR used as a tackifier added to NR prior to vulcanization improved the bonding between vulcanized NR and the PEF.

Encapsulation of acidified chitosan within partially cross-linked natural rubber matrices and their potential slow-release application

Biocomposites comprising acidified chitosan (CTS) encapsulated in partially cross-linked natural rubber (NR) matrices (CTS-e-NR) were prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FE-SEM). The results of FT-IR, TGA and FE-SEM revealed that CTS was merely encapsulated within partially cross-linked natural rubber, and no chemical interaction was observed between CTS and NR. Soil burial biodegradation studies indicated that CTS-e-NR was degraded beyond any doubt, and weight loss of 48.98% was observed within 8 months. The release behaviour of CTS-e-NR was investigated in distilled water, where the naphthols (pesticide precursors) 1-hydroxynaphthalene (1-N), 2-hydroxynaphthalene (2-N), 1,4-dihydroxynaphthalene (1,4-N) and 2,6-dihydroxynaphthalene (2,6-N) were used as model pesticides. The percentage released in the first 24 h was found to be 7.38, 4.39, 2.96 and 6.95%, while 62.69, 60.64, 22.68 and 40.985% was released at the 35th day, for 1-N, 2-N, 1,4-N and 2,6-N, respectively. The release of naphthols followed non-Fickian diffusion: the combination of both polymer erosion and diffusion release mechanisms. In addition, the release behaviour was found to be consistently controlled and prolonged over a period of 35 days. Therefore, CTS-e-NR is strongly recommended for the controlled-release application of real pesticides.

Photocatalytic heterostructures-based BiFeO3 embedded liquid natural rubber (LNR) for highly removal of cationic dye under direct sunlight

Abstract In this study, the composite consists of bismuth ferrite (BiFeO3) photocatalyst embedded into macroporous liquid natural rubber (LNR) matrices was fabricated to assess the removal efficiency of methylene blue (MB) dye under direct sunlight. The structural properties and morphology of LNR-BiFeO3 composite were thoroughly characterised using spectroscopic and microscopic methods. X-Ray diffractogram of the composite demonstrated successful inclusion of BiFeO3 into the LNR network. During solar-driven photocatalytic activity of LNR-BiFeO3, the effects of selected operating parameters on removal efficiency, such as catalyst dose, irradiation time, initial dye concentration, and solution pH, were determined. At optimum catalyst dose (0.15 g BiFeO3) and irradiation time (3 h), degradation of 10 ppm MB was remarkably efficient as 98.9 + 0.09 % have been successfully discarded from the system. The composite had managed to degrade up to 75 ppm MB with degradation efficiency exceeding 89.0 %. In order to investigate the mechanism of MB removal using LNR-BiFeO3, monitoring of removal mode, kinetics and scavenger study were carried out. The outcomes revealed that MB removal did fit well with Langmuir-Hinshelwood kinetic model, in which BiFeO3 (Ebg = 1.76 eV) is responsible for photodegradation process using OH―, O2― and h+ with assistance of adsorption by the composite. The composite could be reused for five cycles without any post-treatment or separation step, and most importantly, no significant loss noted in its activity. This eco-friendly and economical approach will render new opportunities for this advanced photocatalyst as great potential in environmental remediation for wastewater treatment.

Physical-Chemical and Mechanical Characterization of the Bast Fibers of <i>Triumfetta cordifolia</i> A.Rich. from the Equatorial Region of Cameroon

The project consists in the implementation of a biocomposite based on tannin resin and natural rubber matrices with the bast fibres of Triumfetta cordifolia A.Rich.“Okong” from the equatorial region of Cameroon as reinforcement. A study of this still little known fibre is necessary. This paper evaluates the physico-chemical and mechanical characteristics of the fibers. The fibers are extracted by us. A series of experiments is conducted for this purpose: morphological observation with a scanning electron microscope (SEM); density evaluation with a helium pycnometer; absorption rate evaluation according to the protocol available in the literature, Fourier Transform Infrared Spectrometry (FT-IR), chemical composition evaluation according to ASTM 1972 and ASTM 1977 standards, thermogravimetric analysis (TGA) and tensile tests on fiber bundles according to NF T25-501-3. The results show that the fiber is made up of several elementary fibers with oval cross-sections. A density of 1.477g/cm3 close to that of hemp. These fibers have a water absorption rate of 342.5%, which correlates with the presence of free hydroxyl functional groups obtained from the spectrometry study (FT-IR). Chemical analysis reveals that the fiber is made up of celluloses (44.4%), hemicelluloses (30.8%), lignins (18.9%), pectins (3.3%), waxes (0.5%) and minerals (2.1%). In addition, we learn that the fibers studied dehydrate at 11.49%, showinga notable thermal stability around 235°C with a peak thermal decomposition of cellulose located at 420°C. In terms of mechanical behaviour, the results reveal that the fibers offer a Young’s modulus in traction of 12.4 ± 6.9 GPa, a tensile strength of 526 ± 128 MPa and an elongation at break of 2.25%. The information thus obtained makes it possible to place these fibers in the same fiber group as flax and jute. They could therefore be used for the same types of applications. They also inform us that these fibers can withstand the temperatures of composite shaping by thermocompression.

Enhanced fatigue and durability of carbon black/natural rubber composites reinforced with graphene oxide and carbon nanotubes

Graphene oxide (GO) sheets and carbon nanotubes (CNTs) are of nanometer size and offer large shape factors which are beneficial in reducing crack propagation rates of composites when used in carbon black (CB) reinforced natural rubber (NR), thereby prolonging the service lives of rubber composites. In this research, CNT-CB/NR and GO-CB/NR composites were prepared by partially replacing CB with one-dimensional CNTs and two-dimensional flaky graphene oxide GO, respectively. The results showed that the complex filler dispersion in NR matrices was improved due to the isolation effect between the different fillers. The strain-induced crystallization (SIC) ability of CB/NR was effectively enhanced by the addition of both GO and CNT. The modulus at 100% strain and tear strength of the composites were also improved. More branching and deflections were observed at the crack tips of the composites and both effectively hindered crack propagation in the materials. Under uniaxial and multi-axial cyclic loading, the fatigue lives of CNT-CB/NR and GO-CB/NR composites greatly increased when compared with the fatigue lives of CB/NR composites. The GO-CB/NR composites exhibited evident advantages in respect of fatigue resistance and durability among the three composites.

Effects of Poling on Electrical Properties of Flexible Piezoelectric Composites with Natural Rubber Matrix

This work was done to study effects of electrical applied voltage on electrical properties of flexible piezoelectric composites with natural rubber (NR) matrices. Different amounts of lead magnesium niobate titanate (PMNT) as a piezoelectric phase were added into NR matrices. NR/xPMNT (where x = 0, 60, 80, 100, 120 and 150 phr) composites were consequently obtained. The composites were poled under 25 kV/cm electric field for 30 mins. For all the samples, tetragonality is enhanced after poling. Dielectric and ferroelectric properties, and generated electrical voltage of unpoled and poled samples were measured. For the samples with x ≤ 80 phr, the properties are not improved with the poling process. However, for x > 80 phr samples, the properties are significantly enhanced after poling. A percent increase in generated electrical voltage after poling tends to increase with increasing PMNT concentration. The overall result suggests that the NR/100PMNT composite is suitable for applications as high mechanical damage resistance piezoelectric sensors and generators.

Fabrication and characterization of flexible piezoelectric composites with natural rubber matrix

This work aims to fabricate and characterize flexible piezoelectric composites with natural rubber (NR) matrix. Different amounts of Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT) powders were added in NR matrices. Porosity, tensile strength and percent elongation at break of composites tended to decrease with increasing PMNT content. The dielectric constant of the NR materials was found to be 3.5. It was raised up to 4.2, 5.0, 4.5, 4.8 and 5.1 when 60, 80, 100, 120 and 150 phr PMNT powders were added. However, dielectric loss of NR materials did not change with PMNT additions. Among this composite system, the NR/100PMNT composite showed the best piezoelectric properties, which its output voltage, piezoelectric coefficient (d33) and piezoelectric voltage coefficient (g33) values were equal to 1.61 V, 2.1 × 10−4 pC/N and 5.4 × 10−6 V⋅m/N, respectively. This composition composite is a promising material suitable for further improvement to be used as piezoelectric generators in energy harvesting applications.

Hybrid transdermal drug delivery patch made from poly(p‐phenylene vinylene)/natural rubber latex and controlled by an electric field

AbstractA flexible, natural rubber (NR) patch was developed for electrically controllable transdermal drug delivery. NR latex was crosslinked at various crosslinking ratios under the UV curing method. Ibuprofen (Ibu) was the model drug and was used as the dopant for poly(p‐phenylene vinylene) (PPV) acting as the drug encapsulating host. For the pristine Ibu‐loaded NR patch, the amount of Ibu permeation increased with decreasing crosslink density and increasing electrical potential. For the Ibu‐doped PPV/NR patch, the amount of Ibu release−permeation also increased with increasing electrical potential and was higher than that of the pristine NR matrices. Without an applied electric field, the drug remained attached to the PPV during an initial period of 6 h. Under an applied electric field, the oxidation state of the conductive polymer was altered, the iontophoretic effect, pore formation in the NR matrix, expansion of the pore size in hair follicles and PPV chain expansion combined to increase the Ibu release−permeation amount. Thus, the flexible PPV/NR transdermal drug delivery patch was demonstrated to be effective in drug release−permeation based on the strength of the electrical potential, the crosslinking density and the presence of PPV as the encapsulation host. © 2018 Society of Chemical Industry

Rational design of aromatic surfactants for graphene/natural rubber latex nanocomposites with enhanced electrical conductivity

HypothesisGraphene nanoplatelets (GNPs) can be dispersed in natural rubber matrices using surfactants. The stability and properties of these composites can be optimized by the choice of surfactants employed as stabilizers. Surfactants can be designed and synthesized to have enhanced compatibility with GNPs as compared to commercially available common surfactants. Including aromatic groups in the hydrophobic chain termini improves graphene compatibility of surfactants, which is expected to increase with the number of aromatic moieties per surfactant molecule. Hence, it is of interest to study the relationship between molecular structure, dispersion stability and electrical conductivity enhancement for single-, double-, and triple-chain anionic graphene-compatible surfactants. ExperimentsGraphene-philic surfactants, bearing two and three chains phenylated at their chain termini, were synthesized and characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy. These were used to formulate and stabilize dispersion of GNPs in natural rubber latex matrices, and the properties of systems comprising the new phenyl-surfactants were compared with commercially available surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzenesulfonate (SDBS). Raman spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HRTEM) were used to study structural properties of the materials. Electrical conductivity measurements and Zeta potential measurements were used to assess the relationships between surfactant architecture and nanocomposite properties. Small-angle neutron scattering (SANS) was used to study self-assembly structure of surfactants. FindingsOf these different surfactants, the tri-chain aromatic surfactant TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3phenylpropoxy)carbonyl) pentane-2-sulfonate) was shown to be highly graphene-compatible (nanocomposite electrical conductivity = 2.22 × 10−5 S cm−1), demonstrating enhanced electrical conductivity over nine orders of magnitude higher than neat natural rubber-latex matrix (1.51 × 10−14 S cm−1). Varying the number of aromatic moieties in the surfactants appears to cause significant differences to the final properties of the nanocomposites.

Application of advanced polymeric materials for controlled release pesticides

The objective of this work was to study the capability of advanced polymeric material constituted by chitosan and natural rubber matrices for controlled release of pesticides (1-hydroxynaphthalene and 2-hydroxynaphthalene) in aqueous solution. The released amount of pesticides was measured spectrophotometrically from the absorbance spectra applying a standardized curve. The release of the pesticides was studied into refreshing and non-refreshing neutral aqueous media. Interestingly, formulation successfully indicated a consistent, controlled and prolonged release of pesticides over a period of 35 days.

Influence of carbon black with different concentration on dynamic properties and heat buildup of semi‐efficient natural rubber composites

High abrasion furnace black (HAF) filler has long been recognised as reinforcing filler, but the impact of concentration on dynamic mechanics performance and heat buildup of vulcanisates is rarely reported. Therefore, natural rubber (NR) composites filled by N330 with different concentration were prepared. Payne effect and heat buildup of HAF/NR composites increases with an increase of HAF loadings during to that filler network structure become stronger with an increase of HAF loadings. Moreover, tensile strength, tear strength as well as modulus increase with an increase of HAF loadings is attributed to better dispersion and improved interfacial interaction between HAF and NR matrices. The results reveal that composites with 60 per hundreds of rubber (phr) of HAF exhibit better overall mechanical properties and lower heat buildup.

Effect of Cobalt Ferrite Loading on Differential Scanning Calorimetry of Magnetic Polymer Composites

Effects of magnetic cobalt ferrite (CoFe2O4) on thermal properties of polypropylene (PP), polyurethane (PU) and natural rubber (NR) matrices were studied by differential scanning calorimetry. The endothermic peak area of PP was reduced with increasing loading of CoFe2O4 from 0 to 45 % and such peak in semicrystalline PU was entirely absent when the CoFe2O4 loading was over 25 part per hundred rubber. The results indicated that magnetic clusters embedded at the interchain spacing inhibited the nucleation of order segments in polymer matrix. The presence of CoFe2O4 particles also had influence on the mobile amorphous portions of PU chains with polar functional group. No endothermic evidence on the thermograms of non-polar amorphous NR was observed.

Tensile and Dynamic Mechanical Properties of Natural Rubber and Polyurethane Composites Filled with Cobalt Ferrite

Incorporation of magnetic powders into polymers gives rise to electromagnetic properties useful in sensors and electromagnetic wave absorbers. However, such advantageous properties are introduced in polymer composites at the expense of some mechanical properties. This work aims to explore the effects of magnetic cobalt ferrite (CoFe2O4) fillers on the tensile and dynamic mechanical properties of natural rubber (NR) and polyurethane (PU) matrices from 0 to 45 phr prepared using a 2-roll mill. The tensile properties deteriorated in the case of NR whereas the storage modulus was reduced for PU composites. The CoFe2O4 inhibited the crosslinking and orientations to form crystallites in NR and reduced the stiffness of PU due to poor adsorption between the matrix and fillers. One effect in common was the reduced damping coefficient in both NR and PU composites by the incorporation of CoFe2O4.

Preparation and properties of carbon-nanotube composites with natural rubber and epoxidized natural rubber

Composites of carbon-nanotubes (CNTs) and natural rubber (NR), as well as epoxidized natu- ral rubber (ENR), were prepared by melt compounding in an internal mixer. The state of CNT dispersion was determined by examination of the electrical percolation threshold of the composites. The composites with the more polar ENR exhibit a lower percolation threshold than those with NR matrices. It was also shown that two-step processing using an internal mixer and two roll mill resulted in a better CNT disper- sion and lower percolation threshold. The effect of CNTs on vulcanization and crosslinking were investi- gated by oscillating rheometer and DSC measurements. The crosslink densities of the composites were determined by equilibrium swelling measurements as well as hysteresis tensile tests. A significant increase in crosslink densities of the composites with increasing CNT content was detected. Increasing CNT content also resulted in accelerated crosslinking reaction. The thermal conductivity of the compo- sites was tested by DSC measurements. A very large increase of thermal conductivity could be obtained with a low CNT content. However, it turned out that the increase of thermal conductivity is restricted by the thermal resistance at the interface between CNTs and the matrix.