Large deformation mechanical behavior of flexible nanofiber filled polymer nanocomposites

Reinforcement Behavior of Chemically Unmodified Cellulose Nanofiber in Natural Rubber Nanocomposites

We investigated the reinforcement behavior of small amounts of chemically unmodified cellulose nanofiber (CNF) in eco-friendly natural rubber (NR) nanocomposites. For this purpose, NR nanocomposites filled with 1, 3, and 5 parts per hundred rubber (phr) of cellulose nanofiber (CNF) were prepared by a latex mixing method. By using TEM, a tensile test, DMA, WAXD, a bound rubber test, and gel content measurements, the effect of CNF concentration on the structure-property relationship and reinforcing mechanism of the CNF/NR nanocomposite was revealed. Increasing the content of CNF resulted in decreased dispersibility of the nanofiber in the NR matrix. It was found that the stress upturn in the stress-strain curves was remarkably enhanced when the NR was combined with 1-3 phr CNF, and a noticeable increase in tensile strength (an approximately 122% increase in tensile strength over that of NR) was observed without sacrificing the flexibility of the NR in the NR filled with 1 phr CNF, though no acceleration in their strain-induced crystallization was observed. Since the NR chains were not inserted in the uniformly dispersed CNF bundles, the reinforcement behavior by the small content of CNF might be attributed to the shear stress transfer at the CNF/NR interface through the interfacial interaction (i.e., physical entanglement) between the nano-dispersed CNFs and the NR chains. However, at a higher CNF filling content (5 phr), the CNFs formed micron-sized aggregates in the NR matrix, which significantly induced the local stress concentration and promoted strain-induced crystallization, causing a substantially increased modulus but reduced the strain at the rupture of the NR.

An Implantable Transparent Conductive Film with Water Resistance and Ultrabendability for Electronic Devices

Recently, instead of indium tin oxide, the random mesh pattern of metallic nanowires for flexible transparent conducting electrodes (FTCEs) has received a great amount of interest due to its flexibility, low resistance, reasonable price, and compliant processes. Mostly, nanowires for FTCEs are fabricated by spray or mayer coating methods. However, the metallic nanowire layer of FTCEs, which is fabricated by these methods, has a spiked surface roughness and low junction contact between the nanowires that lead to their high sheet resistance value. Also, the nanowires on FTCEs are easy to peel-off through exterior forces such as bending, twisting, or contact. To solve these problems, we demonstrate novel methods through which silver nanowires (AgNWs) are deposited onto a nanosize porous nitrocellulose (NC) substrate by electrophoretic deposition (EPD) and an opaque and porous substrate. Respectively, through dimethyl sulfoxide treatment, AgNWs on NC (AgNW/NC) is changed to the transparent and nonporous FTCEs. This enhances the junction contact of the AgNWs by EPD and also allows a permanent attachment of AgNWs onto the substrate. To show the mechanical strength of the AgNWs on the transparent nitrocellulose (AgNW/TNC), it is tested by applying diverse mechanical stress, such as a binding test (3M peel-off), compressing, bending, twisting, and folding. Next, we demonstrate that AgNW/TNC can be effectively implanted onto normal newspapers and papers. As paper electronics, light-emitting diodes, which are laminated onto paper, are successfully operated through a basic AgNW/TNC strip circuit. Finally, it is demonstrated that AgNW/TNC and AgNW/TNC on paper are water resistant for 15 min due to the insulation properties of the nonporous substrate.

Preparation and characterization of poly (phenylene sulfide) nanocomposites with both silica and clay fillers

Poly (phenylene sulfide) (PPS)/silica (SiO2)/organophilic montmorillonite OMMT(clay) nanocomposites are prepared and two kinds of nanofillers of different dimensions, the plate-like OMMT(clay) and globe-like SiO2, are dispersed through their “filler–filler” interaction in melt processing. In PPS/SiO2/clay system, strong filler–filler interaction is established by different responses to shear flow of inorganic clay and SiO2, thus the well dispersion of nanofillers is achieved successfully. However, the OMMT platelets are prone to be entangled by PPS molecular chains in PPS/SiO2/OMMT composites due to the extremely low interfacial tension between PPS and OMMT, which blocks the interaction between OMMT and SiO2. The result reveals two key points in realizing well dispersion of nanofillers in polymer by establishing filler–filler interaction in processing, namely, the distinct responses to shear flow of nanofillers provide an important condition for filler–filler interaction, while the direct collision between each other is another key point to successfully realize this interaction.

Cellulose nanomaterials review: structure, properties and nanocomposites

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

Polysaccharide nano crystal reinforced nanocomposites

There are numerous examples of animals or plants that synthesize extracellular high-performance skeletal biocomposites consisting of a matrix reinforced by nano sized crystalline domains. Cellulose and chitin are classical examples of these reinforcing elements, which occur as whisker-like microfibrils that are biosynthesized and deposited in a continuous fashion. In many cases, this mode of biogenesis leads to crystalline microfibrils that are almost defect-free, and whose axial physical properties therefore approach those of perfect crystals. During the last decade we have attempted to mimic biocomposites by blending cellulose or chitin whiskers from different sources with polymer matrices. Aqueous suspensions of such nano crystals can be prepared by acid hydrolysis of the substrate. The object of this treatment is to dissolve away regions of low lateral order so that the water-insoluble, highly crystalline residue may be converted into a stable suspensoid by subsequent vigorous mechanical shearing action. The resulting nano crystals occur as rod-like particles or whiskers, whose dimensions depend on the nature of the substrate. They are typically a few hundred nm long and between 5 and 20 nm in diameter. Starch can also be used as a source for the production of nano crystals. The constitutive nano crystals appear as platelet-like nano particles with a length ranging between 20 and 40 nm, a width ranging between 15 and 30 nm, and a thickness ranging between 5 and 7 nm. Since the first announcement of using cellulose whiskers as a reinforcing phase, they have been used extensively as model fillers in several kinds of polymeric matrices, including synthetic and natural ones. Casting mixtures of polysaccharide nano crystals and lattices led to the production of nano composite materials with drastically enhanced mechanical properties, especially at T > Tg of the matrix, by virtue of the formation of a whiskers network, even when the whisker volume fraction was only a few percent. The formation of this rigid network, resulting from strong interactions between whiskers, was assumed to be governed by a percolation mechanism. This hydrogen-bonded network induced a thermal stabilization of the composite up to 500 K, the temperature at which polysaccharides start to decompose. Any factors that perturb the formation of this percolating network directly affect the reinforcing effect of polysaccharide nano crystals. In addition to some practical applications, the study of these nano composite materials can help researchers understand such physical properties as the geometric and mechanical percolation effect.Key words: nano composites, polysaccharide, polymer, cellulose, nano crystal.