The incorporation of carbon nanofibres to enhance the properties of self reinforced, single polymer composites

Compatibilizer Polarity Parameters as Tools for Predicting Organoclay Dispersion in Polyolefin Nanocomposites

Nanocomposites give an innovative method to increase the mechanical, thermal, and barrier performance of polymers. However, properly dispersing the nanoparticles in the polymer matrix is often key in achieving high performance, especially in the case of hydrophilic nanoparticles and hydrophobic polymers. For that purpose, nanoparticles may be functionalized with organic groups to increase their affinity with the polymer matrix. Compatibilizing agents may also be included in the nanocomposite formulation. This paper aims at identifying parameters relative to the compatibilizer polarity that would allow predicting nanoparticle dispersion in the polymer nanocomposite. The analysis used published data on nanocomposite samples combining clay nanoparticles, polyolefins, and various compatibilizing agents. We studied the correlations between the nanoclay exfoliation ratio and five different parameters describing the compatibilizer hydrophilic-lipophilic balance: the acid value, the mole, and weight fraction of polar groups, the number of polymer chain units per polar group, and the number of moles of polar groups per mole of compatibilizer. The best correlation was observed with the number of polymer chain units per polar group in the compatibilizer. This parameter could be used as a tool to predict the dispersion of organoclay nanoparticles in polyolefins. Another important result of the study is that, among the compatibilizers investigated, those with a low acid value provided a better nanoclay exfoliation compared to those with a high acid value. This may indicate the existence of a maximum in the nanoclay exfoliation/compatibilizer polarity curve, which would open new perspectives for nanocomposite performance optimization.

Carbon nanofiber reinforced thermoplastic elastomer based on polypropylene/polybutadiene blend: theoretical modeling of Young’s modulus of the nanocomposites with respect to the orientation and agglomeration of carbon nanofiber

The effect of the concentration of carbon nanofibers (CNFs) on thermoplastic elastomer based on polypropylene/polybutadiene (PP/BR) blend (80/20) prepared by melt blending process was investigated. The morphological properties are reported in combination with the mechanical and rheological properties of the nanocomposites. The dispersion of CNFs examined by transmission electron microscopy shows uniform dispersion of CNFs in the PP matrix. The mechanical performance is found to be in line with the morphological structure observed in scanning electron microscopy. Tensile strength and Young’s modulus of the PP/BR blend increase with an increase of filler content up to 3 wt%. The modified Halpin-Tsai equation that accounts for the effect of orientation and agglomeration of CNF was used to evaluate the Young’s modulus of the nanocomposite. The dynamic rheological analysis in the frequency sweep experiment shows that the introduction of CNF in the PP/BR blend improves the complex viscosity (ƞ*), storage modulus (G′), and loss modulus (G″) in the low-frequency region.

Uncovering three-dimensional gradients in fibrillar orientation in an impact-resistant biological armour

The complex hierarchical structure in biological and synthetic fibrous nanocomposites entails considerable difficulties in the interpretation of the crystallographic texture from diffraction data. Here, we present a novel reconstruction method to obtain the 3D distribution of fibres in such systems. An analytical expression is derived for the diffraction intensity from fibres, explaining the azimuthal intensity distribution in terms of the angles of the three dimensional fibre orientation distributions. The telson of stomatopod (mantis shrimp) serves as an example of natural biological armour whose high impact resistance property is believed to arise from the hierarchical organization of alpha chitin nanofibrils into fibres and twisted plywood (Bouligand) structures at the sub-micron and micron scale. Synchrotron microfocus scanning X-ray diffraction data on stomatopod telson were used as a test case to map the 3D fibre orientation across the entire tissue section. The method is applicable to a range of biological and biomimetic structures with graded 3D fibre texture at the sub-micron and micron length scales.

Ultrasound Assisted Single Screw Extrusion Process for Dispersion of Carbon Nanofibers in Polymers

A novel method for the continuous dispersion of carbon nanofibers (CNFs) in a polymer matrix for manufacturing high performance nanocomposites was developed using an ultrasonically assisted single screw extrusion process. The effect of ultrasound on die pressure, electrical and thermal conductivity, rheological, morphological and mechanical properties of polyetherimide (PEI) filled with 1 to 20 wt.% CNFs was studied. A reduction in the die pressure and percolation threshold of CNF/PEI nanocomposites with a permanent increase in the viscosity and a permanent decrease in tan δ was achieved through ultrasonic treatment. Morphological studies of the treated nanocomposites revealed their improved homogeneity leading to an increase of the Young's modulus and electrical and thermal conductivity.

Microstructure and Properties of Polypropylene/Carbon Nanotube Nanocomposites

In the last few years, great attention has been paid to the preparation of polypropylene (PP) nanocomposites using carbon nanotubes (CNTs) due to the tremendous enhancement of the mechanical, thermal, electrical, optical and structural properties of the pristine material. This is due to the unique combination of structural, mechanical, electrical, and thermal transport properties of CNTs. However, it is well-known that the properties of polymer-based nanocomposites strongly depend on the dispersion of nanofillers and almost all the discussed properties of PP/CNTs nanocomposites are strongly related to their microstructure. PP/CNTs nanocomposites were, mainly, prepared by melt mixing and in situ polymerization. Young’s modulus, tensile strength and storage modulus of the PP/CNTs nanocomposites can be increased with increasing CNTs content due to the reinforcement effect of CNTs inside the polymer matrix. However, above a certain CNTs content the mechanical properties are reduced due to the CNTs agglomeration. The microstructure of nanocomposites has been studied mainly by SEM and TEM techniques. Furthermore, it was found that CNTs can act as nucleating agents promoting the crystallization rates of PP and the addition of CNTs enhances all other physical properties of PP. The aim of this paper is to provide a comprehensive review of the existing literature related to PP/CNTs nanocomposite preparation methods and properties studies.