Elastomer Nanocomposites: Effect of Filler-Matrix and Filler-Filler Interactions

The reinforcement of elastomers is essential in the rubber industry in order to obtain the properties required for commercial applications. The addition of active fillers in an elastomer usually leads to an improvement in the mechanical properties such as the elastic modulus and the rupture properties. Filled rubbers are also characterized by two specific behaviors related to energy dissipation known as the Payne and the Mullins effects. The Payne effect is related to non-linear viscoelastic behavior of the storage modulus while the Mullins or stress-softening effect is characterized by a lowering in the stress when the vulcanizate is extended a second time. Both effects are shown to strongly depend on the interfacial adhesion and filler dispersion. The basic mechanisms of reinforcement are first discussed in the case of conventional rubber composites filled with carbon black or silica usually present in the host matrix in the form of aggregates and agglomerates. The use of nanoscale fillers with isotropic or anisotropic morphologies is expected to yield much more improvement than that imparted by micron-scale fillers owing to the very large polymer-filler interface. This work reports some results obtained with three types of nanoparticles that can reinforce rubbery matrices: spherical, rod-shaped and layered fillers. Each type of particle is shown to impart to the host medium a specific reinforcement on account of its own structure and geometry. The novelty of this work is to emphasize the particular mechanical behavior of some systems filled with nanospherical particles such as in situ silica-filled poly(dimethylsiloxane) networks that display a strong polymer-filler interface and whose mechanical response is typical of double network elastomers. Additionally, the potential of carbon dots as a reinforcing filler for elastomeric materials is highlighted. Different results are reported on the reinforcement imparted by carbon nanotubes and graphenic materials that is far below their expected capability despite the development of various techniques intended to reduce particle aggregation and improve interfacial bonding with the host matrix.

Potential Utilization of Ground Eggshells as a Biofiller for Natural Rubber Biocomposites

The aim of this work was application of ground eggshells in various amounts by weight as a biofiller for natural rubber (NR) biocomposites. Cetyltrimethylammonium bromide (CTAB), ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride (BmiCl) and 1-decyl-3-methylimidazolium bromide (DmiBr), and silanes, i.e., (3-aminopropyl)-triethoxysilane (APTES) and bis [3-(triethoxysilyl)propyl] tetrasulfide (TESPTS), were used to increase the activity of ground eggshells in the elastomer matrix and to ameliorate the cure characteristics and properties of NR biocomposites. The influence of ground eggshells, CTAB, ILs, and silanes on the crosslink density, mechanical properties, and thermal stability of NR vulcanizates and their resistance to prolonged thermo-oxidation were explored. The amount of eggshells affected the curing characteristics and crosslink density of the rubber composites and therefore their tensile properties. Vulcanizates filled with eggshells demonstrated higher crosslink density than the unfilled sample by approximately 30%, whereas CTAB and ILs increased the crosslink density by 40-60% compared to the benchmark. Owing to the enhanced crosslink density and uniform dispersion of ground eggshells, vulcanizates containing CTAB and ILs exhibited tensile strength improved by approximately 20% compared to those without these additives. Moreover, the hardness of these vulcanizates was increased by 35-42%. Application of both the biofiller and the tested additives did not significantly affect the thermal stability of cured NR compared to the unfilled benchmark. Most importantly, the eggshell-filled vulcanizates showed improved resistance to thermo-oxidative aging compared to the unfilled NR.

Mechanical properties and thermal analysis of graphene nanoplatelets reinforced polyimine composites

The polymer with imine bonds (C═N) synthesized by condensation of aldehydes and amines was called polyimine. Graphene nanoplatelets (GNPs) were blended into polyimine by imine dynamic chemistry, and GNPs/polyimine (GNPs-P) composites were fabricated by heat-pressing. A series of thermal and mechanical properties have been tested for the matrix and GNPs-P composites. Thermogravimetric analyzer showed that the GNPs were able to improve the thermal stability of the GNPs-P composites. From the test of mechanical properties, GNPs-P composite with 0.5 wt% GNPs was superior to the matrix in bending and tensile properties. The bending and tensile strengths were 92.65 and 73.05 MPa, with an improvement of 18% and 5%. GNPs-P composites with 1 wt% GNPs showed the most significant advancement in impact properties, reaching an impact strength of 11.745 kJ·m−2 with a gain of 21.6%. Cross-sectional observations using scanning electron microscope proved that the GNPs-P composites have brittle fractures. A small number of GNPs could synergize with the matrix by bridging the cracks, creating a crack diffusion resistance and a load transfer reinforcement effect, which improved the mechanical properties of the GNPs-P composites.

Testing of Silicon Rubber/Montmorillonite Nanocomposite for Mechanical and Tribological Performance

Nanocomposite made by blending nano-montmorillonite (MMT) and Silicon Rubber (SR) for mechanical and tribological performance is explored in this work. Different configurations of MMT/SR nanocomposite, with 0, 0.5, 2 and 5 wt % of MMT are manufactured by two roll mixing methods. Noticeable improvement in the mechanical and tribological performance is observed, which is also justified by a morphological study of fractured and wear surfaces through SEM. Two percent of MMT loading is found to be the optimum content that shows excellent performance compared to other compositions. The performance improvement can be linked to the good interfacial interaction between the MMT and SR. Statistical modeling through ANOVA is carried out for tribological performance, which reveals the influence of load on the coefficient of friction (COF) and the influence of sliding distance on the wear rate.

Investigation on in situ silica dispersed in natural rubber latex matrix combined with spray sputtering technology

In this study, different processes are performed for the preparation of natural rubber latex (NRL)/silica composites. A novel approach is to use spray sputtering technology combined with in situ method to improve the dispersion of silica in rubber latex matrix and further improve the properties of vulcanizates. Results show that in situ silica in rubber matrix prepared from NH4Cl and Na2SiO3 has better Payen effect than other processes. Meanwhile, when the in situ silica reached 10 phr in the rubber matrix, the dosage can suitably match the dispersion capacity of the spray sputtering process with superior comprehensive mechanical properties. Compared with the traditional precipitation method, the tensile strength and tear strength of the silica/NR composites prepared by spray sputtering technology combined with in situ method were increased by 34.7% and 19.7%.

Mechanochemical Synthesis of Rosin-Modified Montmorillonite: A Breakthrough Approach to the Next Generation of OMMT/Rubber Nanocomposites

The current investigation presents a green mechanochemical procedure for the synthesis of a special kind of rubber-compatible organo-montmorillonite (OMMT) for use in the inner liner compound of tires. The compatibility character of the OMMT arises from the mechanochemical reaction of the raw bentonite mineral and gum rosin as some of the organic constituents of the inner liner composition. The monitoring of OMMT synthesis by various characterization techniques reveals that gum rosin gradually intercalates into the montmorillonite (MMT) galleries during milling and increases the interlayer spacing to 41.1 ± 0.5 Å. The findings confirm the simultaneous formation of single- or few-layered OMMT platelets with average sizes from the sub-micron range up to several micrometers during the milling process. The mechanical properties of the OMMT/rubber nanocomposite, such as tensile strength, tear resistance and elongation, present a good enhancement in comparison to the un-modified material. Moreover, the organo-modification of the inner liner composition also leads to a property improvement of about 50%.

Natural rubber latex/MXene foam with robust and multifunctional properties

Low strength has always been one of the main factors limiting the application of foams. We acquire a natural rubber latex/MXene foam composite with high strength and versatility by adding MXene to the natural rubber latex. It is shown that natural rubber latex foam (NRF) with 2 and 3 phr of MXene shows obviously enhanced tensile strength by 171% and 157% separately as compared to that of neat NRF. Furthermore, the composite also has better electrical conductivity and electromagnetic shielding than NRF, which can be used in the automotive industry, aviation industry, and many other aspects.

Mechanical properties and application analysis of spider silk bionic material

Spider silk is a kind of natural biomaterial with superior performance. Its mechanical properties and biocompatibility are incomparable with those of other natural and artificial materials. This article first summarizes the structure and the characteristics of natural spider silk. It shows the great research value of spider silk and spider silk bionic materials. Then, the development status of spider silk bionic materials is reviewed from the perspectives of material mechanical properties and application. The part of the material characteristics mainly describes the biocomposites based on spider silk proteins and spider silk fibers, nanomaterials and man-made fiber materials based on spider silk and spider-web structures. The principles and characteristics of new materials and their potential applications in the future are described. In addition, from the perspective of practical applications, the latest application of spider silk biomimetic materials in the fields of medicine, textiles, and sensors is reviewed, and the inspiration, feasibility, and performance of finished products are briefly introduced and analyzed. Finally, the research directions and future development trends of spider silk biomimetic materials are prospected.