Compatibilization and properties of ethylene vinyl acetate copolymer (EVA) and thermoplastic polyurethane (TPU) blend based foam

Influence of TPU/EVA Phase Morphology Evolution on Supercritical Carbon Dioxide Extrusion Foaming

Ethylene-vinyl acetate copolymer (EVA) was added at different contents to the thermoplastic polyurethane (TPU) matrix to form a non-compatible blending system, and foaming materials with high pore density were prepared using the supercritical carbon dioxide extrusion method. The influence of the phase morphology and crystal morphology of the TPU/EVA blend on its foaming behavior was studied. The results show that EVA changed the phase morphology and crystal morphology of the blends, leading to the improved melt viscosity and crystallinity of the blend system. At the same time, interfacial nucleation increases the density of cells and decreases the cell thickness and size, which is beneficial for improving the foaming properties of the blends. For the EVA content of 10% (mass fraction), the cell size is small (105.29 μm) and the cell density is the highest (3.74 × 10⁶ cells/cm³). Based on the TPU/EVA phase morphology and crystal morphology, it is found that the sea-island structure of the blend has better foaming properties than the bicontinuous structure.

Matrix-filler interactions and solvent sorption features of nanohydroxyapatite (nHA) embedded ethylene-co-vinyl acetate (EVA)-millable polyurethane (MPU) blends

We report the solvent sorption features and matrix filler interactions of nanohydroxyapatite (nHA) embedded ethylene-co-vinyl acetate (EVA)-millable polyurethane (MPU) blends, using toluene, xylene, and t-butylacetate as probe molecules. The EVA/MPU blends were initially loaded with different quantities of n-HA, and the interfacial interactions were evaluated through FTIR and XRD techniques. The modulation of solvent resistance was subsequently examined in terms of filler loading, temperature and molar volume of the probes. With an increase in the amount of nHA, the solvent resistance of the matrix has been found to be enhanced, with the mechanism of transport regularly deviating from the conventional Fickian mode normally followed by elastomer matrices. The Flory-Rehner equation was employed to compute the molecular mass between crosslinks (M_c) and the crosslink density (γ). The observed enhancement in the crosslink density and the degree of reinforcement has been attributed to the increased polar-polar interactions after nHA loading into the matrix. The experimentally obtained values of M_c have been compared with phantom and affine models, to identify the type of deformation happening under solvent stress. The reinforcement effect within the matrix, as a function of filler loading, has been verified by using the Kraus equation. The swelling resistance of the composites has also been verified in biological fluids in view of the possible biofield applications of the composites.

A Comprehensive Review on Corn Starch-Based Nanomaterials: Properties, Simulations, and Applications

Corn (Zea mays L.) is one of the major food crops, and it is considered to be a very distinctive plant, since it is able to produce a large amount of the natural polymer of starch through its capacity to utilize large amounts of sunlight. Corn starch is used in a wide range of products and applications. In recent years, the use of nanotechnology for applications in the food industry has become more apparent; it has been used for protecting against biological and chemical deterioration, increasing bioavailability, and enhancing physical properties, among other functions. However, the high cost of nanotechnology can make it difficult for its application on a commercial scale. As a biodegradable natural polymer, corn starch is a great alternative for the production of nanomaterials. Therefore, the search for alternative materials to be used in nanotechnology has been studied. This review has discussed in detail the properties, simulations, and wide range of applications of corn starch-based nanomaterials.

Enhanced performances of triboelectric nanogenerators by filling hierarchical flower-like TiO2 particles into polymethyl methacrylate film

In this study, a flower-like TiO₂ filled polymethyl methacrylate (PMMA) composite is presented as a positive tribo-material to produce an excellent-performance triboelectric nanogenerator (TENG). By working in conjunction with polydimethylsiloxane (PDMS), the flat-surface PDMS/PMMA-flower TiO₂ TENG generates a voltage of 1200 V, a current of 139 mA m^-2 and an output power of 34.85 W m^-2, showing significant enhancement compared with its counterpart utilizing neat PMMA as the positive tribo-material under the same operating conditions, whose voltage is 620 V, current is 78 mA m^-2 and output power is 13.89 W m^-2, respectively. The performance of the TENG is highly dependent on filler loadings of TiO₂ flower particles in PMMA composites with an optimal filler loading of 40 wt% with the highest performances. The flower TiO₂ is vital to the enhanced performances of the TENG, which is due to the modified surface, the tailored dielectric constant and the space charge polarization. The TENG is capable of powering 600 light emitting diodes, a calculator and a digit display, and applied in self-powered electrophoretic deposition of oxide films. This work demonstrates a facile, low-cost approach for obtaining high-performance TENGs utilizing a PMMA-flower TiO₂ composite as the positive tribo-material for applications in sustainable power systems.

The Synergy of Double Cross-linking Agents on the Properties of Styrene Butadiene Rubber Foams

Sulfur (S) cross-linking styrene butadiene rubber (SBR) foams show high shrinkage due to the cure reversion, leading to reduced yield and increased processing cost. In this paper, double cross-linking system by S and dicumyl peroxide (DCP) was used to decrease the shrinkage of SBR foams. Most importantly, the synergy of double cross-linking agents was reported for the first time to our knowledge. The cell size and its distribution of SBR foams were investigated by FESEM images, which show the effect of DCP content on the cell structure of the SBR foams. The relationships between shrinkage and crystalline of SBR foams were analyzed by the synergy of double cross-linking agents, which were demonstrated by FTIR, Raman spectra, XRD, DSC and TGA. When the DCP content was 0.6 phr, the SBR foams exhibit excellent physical and mechanical properties such as low density (0.223 g/cm³), reduced shrinkage (2.25%) and compression set (10.96%), as well as elevated elongation at break (1.78 × 10³%) and tear strength (54.63 N/mm). The results show that these properties are related to the double cross-linking system of SBR foams. Moreover, the double cross-linking SBR foams present high electromagnetic interference (EMI) shielding properties compared with the S cross-linking SBR foams.