Polyamide 6/Poly(vinylidene fluoride) Blend-Based Nanocomposites with Enhanced Rigidity: Selective Localization of Carbon Nanotube and Organoclay

Effects of Orientation and Dispersion on Electrical Conductivity and Mechanical Properties of Carbon Nanotube/Polypropylene Composite

The orientation and dispersion of nanoparticles can greatly influence the conductivity and mechanical properties of nanocomposites. In this study, the Polypropylene/ Carbon Nanotubes (PP/CNTs) nanocomposites were produced using three different molding methods, i.e., compression molding (CM), conventional injection molding (IM), and interval injection molding (IntM). Various CNTs content and shear conditions give CNTs different dispersion and orientation states. Then, three electrical percolation thresholds (4 wt.% CM, 6 wt.% IM, and 9 wt.% IntM) were obtained by various CNTs dispersion and orientations. Agglomerate dispersion (Adis), agglomerate orientation (Aori), and molecular orientation (Mori) are used to quantify the CNTs dispersion and orientation degree. IntM uses high shear to break the agglomerates and promote the Aori, Mori, and Adis. Large Aori and Mori can create a path along the flow direction, which lead to an electrical anisotropy of nearly six orders of magnitude in the flow and transverse direction. On the other hand, when CM and IM samples already build the conductive network, IntM can triple the Adis and destroy the network. Moreover, mechanical properties are also been discussed, such as the increase in tensile strength with Aori and Mori but showing independence with Adis. This paper proves that the high dispersion of CNTs agglomerate goes against forming a conductivity network. At the same time, the increased orientation of CNTs causes the electric current to flow only in the orientation direction. It helps to prepare PP/CNTs nanocomposites on demand by understanding the influence of CNTs dispersion and orientation on mechanical and electrical properties.

Polycarbonate/Poly(vinylidene fluoride)-Blend-Based Nanocomposites-Effect of Adding Different Carbon Nanofillers/Organoclay

Carbon black (CB), carbon nanotubes (CNTs), and graphene nanoplatelets (GnPs) individually or doubly served as reinforcing fillers in polycarbonate (PC)/poly(vinylidene fluoride) (PVDF)-blend (designated CF)-based nanocomposites. Additionally, organo-montmorillonite (15A) was incorporated simultaneously with the individual carbon fillers to form hybrid filler nanocomposites. Microscopic images confirmed the selective localization of carbon fillers, mainly in the continuous PC phase, while 15A located in the PVDF domains. Differential scanning calorimetry results showed that blending PVDF with PC or forming single/double carbon filler composites resulted in lower PVDF crystallization temperature during cooling. However, PVDF crystallization was promoted by the inclusion of 15A, and the growth of β-form crystals was induced. The rigidity of the CF blend increased after the formation of nanocomposites. Among the three individually added carbon fillers, GnPs improved the CF moduli the most; the simultaneous loading of CNT/GnP resulted in the highest moduli by up to 33%/46% increases in tensile/flexural moduli, respectively, compared with those of the CF blend. Rheological viscosity results showed that adding CNTs increased the complex viscosity of the blend to a greater extent than did adding CB or GnPs, and the viscosity further increased after adding 15A. The electrical resistivity of the blend decreased with the inclusion of carbon fillers, particularly with CNT loading.

Properties of Styrene-Maleic Anhydride Copolymer Compatibilized Polyamide 66/Poly (Phenylene Ether) Blends: Effect of Blend Ratio and Compatibilizer Content

Two different blend ratios of polyamide 66 (PA66) and poly (2,6-dimethyl-1,4-phenylene ether) (PPE) (60/40 and 40/60 w/w) were produced via melt mixing. A styrene-maleic anhydride copolymer (SMA) was utilized at various contents from 2.5-15 wt% to compatibilize the immiscible blend system. The influence of SMA content and blend ratio was investigated based on (thermo-) mechanical and morphological properties of the PA66/PPE blends. Correlations between the interaction of SMA with the blend partners were established. For 60/40 blends, a droplet-sea morphology was visualized by transmission electron microscopy, wherein no major changes were seen upon SMA addition. In the case of 40/60 blends, strong coalescence was found in the binary blend. Up to 5 wt% SMA, the coalescence was inhibited by the interfacial activity of SMA, whereas 10 wt% SMA initiated a disperse-to-co-continuous transition, which was completed at 15 wt% SMA. An enhancement of tensile properties was achieved for all blends possessing SMA, where the maximum concentration of 15 wt% resulted in the highest elongation at break and tensile strength values. The relative improvement of the tensile properties was higher with the PPE-rich blend (40/60) which was attributed to a partial emulsification of the PPE phases forming a bimodal PPE domain size distribution with nano-droplets in the range of 60-160 nm.

Underutilized Agricultural Co-Product as a Sustainable Biofiller for Polyamide 6,6: Effect of Carbonization Temperature

Polyamide 6,6 (PA66)-based biocomposites with low-cost carbonaceous natural fibers (i.e., soy hulls, co-product from soybean industry) were prepared through twin-screw extrusion and injection molding. The soy hull natural fiber was pyrolyzed at two different temperatures (500 °C and 900 °C denoted as BioC500 and BioC900 respectively) to obtain different types of biocarbons. The BioC500 preserved a higher number of functional groups as compared to BioC900. Higher graphitic carbon content was observed on the BioC900 than BioC500 as evident in Raman spectroscopy. Both biocarbons interact with the PA66 backbone through hydrogen bonding in different ways. BioC900 has a greater interaction with N-H stretching, while BioC500 interacts strongly with the amide I (C=O stretching) linkage. The BioC500 interrupts the crystallite growth of PA66 due to strong bond connection while the BioC900 promotes heterogeneous crystallization. Dynamic mechanical analysis shows that both biocarbons result in an increasing storage modulus and glass transition temperature with increasing content in the BioC/PA66 biocomposites over PA66. Rheological analysis shows that the incorporation of BioC900 results in decreasing melt viscosity of PA66, while the incorporation of BioC500 results in increasing the melt viscosity of PA66 due to greater filler-matrix adhesion. This study shows that pyrolyzed soy hull natural fiber can be processed effectively with a high temperature (>270 °C) engineering plastic for biocomposites fabrication with no degradation issues.