Effect of organoclay on the morphology, phase stability and mechanical properties of polypropylene/polystyrene blends

Effect of Different Compatibilization Systems on the Rheological, Mechanical and Morphological Properties of Polypropylene/Polystyrene Blends

The influence of reactive processing, non reactive and reactive copolymers on immiscible polypropylene (PP)–polystyrene (PS) blends with varying PS concentrations (10 wt.% and 25 wt.%) was evaluated by mechanical (tensile and tensile impact), rheological (melt flow rate, extensional and dynamic rheology) and morphological (scanning electron microscopy) analysis. As an extended framework of the study, the creation of a link to industrial applicable processing conditions as well as an economically efficient use of compatibilzing agent were considered. For radical processed blends, a high improvement in melt strength was observed while non reactive copolymers exhibited a pronounced increase in toughness and ductility correlated with overall best phase homogeneity. Conversely, the influence of the reactive copolymer was quite different for the varied PS concentrations not allowing the assumption of a specific trend for resulting blend properties, but nevertheless in the case of a lower PS concentration the tensile impact strength exceeded the value of virgin PP. Since PS and PP are widely used, the findings of this work could not only be relevant for the generation of more versatile blends compared to virgin components but also for recycling purposes, allowing the enhancement of specific properties facilitating the production of more valuable secondary materials.

Pseudo-Ductility, Morphology and Fractography Resulting from the Synergistic Effect of CaCO3 and Bentonite in HDPE Polymer Nano Composite

Polymeric materials such as High density polyethylene(HDPE) are ductile in nature, having very low strength. In order to improve strength by non-treated rigid fillers, polymeric materials become extremely brittle. Therefore, this work focuses on achieving pseudo-ductility (high strength and ductility) by using a combination of rigid filler particles (CaCO3 and bentonite) instead of a single non-treated rigid filler particle. The results of all tensile-tested (D638 type i) samples signify that the microstructural features and surface properties of rigid nano fillers can render the required pseudo-ductility. The maximum value of tensile strength achieved is 120% of the virgin HDPE, and the value of elongation is retained by 100%. Furthermore, the morphological and fractographic analysis revealed that surfactants are not always going to obtain polymer-filler bonding, but the synergistic effect of filler particles can carry out sufficient bonding for stress transfer. Moreover, pseudo-ductility was achieved by a combination of rigid fillers (bentonite and CaCO3) when the content of bentonite dominated as compared to CaCO3. Thus, the achievement of pseudo-ductility by the synergistic effect of rigid particles is the significance of this study. Secondly, this combination of filler particles acted as an alternative for the application of surfactant and compatibilizer so that adverse effect on mechanical properties can be avoided.

Development of an Immiscible Polymer/Polymer/Nanoparticle System to Assess the Location of Nanoparticles by Quantitative Optical Microscopy

The thermo-optical behavior of immiscible PS/PC blends filled with silica nanoparticles was studied in order to get some information upon the location of nanoparticles in the polymer blend phases and interface using optical microscopy. The systems were designed taking into account rheological and optical requirements, having droplet-matrix morphology, with particle size in the range of the visible light wavelength. The melt blending procedure helped to set the nanoparticles at specific locations including within the PC minor phase, PS matrix phase and PS/PC interphase, which was confirmed via transmission electron microscopy. The light scattering was measured via the normalized transmitted light intensity over temperature, encompassing the Tg of the two polymers. The PS/PC blends showed an increase in the light scattering as compared to the pure polymers, which is magnified upon increasing the PC content. The addition of the nanosilica forming PS/PC/Nanosilica systems greatly reduces the light scattering, particularly above the Tg of the PS phase. The use of hydrophilic nanosilica does not show any appreciable hysteresis upon comparing data from heating and cooling cycles. This type of silica stays mainly trapped within the PC dispersed phase, little interfering with the light scattering, which happens at the polymer-polymer interface. On the other hand, the use of hydrophobic nanosilica does show a clear hysteresis. The hydrophobic silica located at the PS/PC interphase, interfere with the light scattering intensity at this interface, and can be used to identify its presence. The proposed procedure can help control the mixing process, thus improving the effective action of the nanoparticles in the final properties of polymer systems.

Development of hybrid composites for automotive applications: effect of addition of SEBS on the morphology, mechanical, viscoelastic, crystallization and thermal degradation properties of PP/PS–xGnP composites

The presence of SEBS and xGnP in PP/PS blend allows better stress transfer between the phases.

Morphology Control and Stabilization in Immiscible Polypropylene and Polyamide 6 Blends with Organoclay

In the current study, 70/30 (w/w) polypropylene (PP)/polyamide 6 (PA6)/organoclay ternary blends were prepared by melt mixing in three different blending sequences, i. e., organoclay premixed with PA6 and then mixed with PP (S1 blending sequence), organoclay premixed with PP and then mixed with PA6 (S2 blending sequence), and organoclay, PA6 and PP mixed simultaneously (S3 blending sequence). The effects of organoclay on the phase morphologies, rheological properties and mechanical properties of the blends are examined to reveal the role of organoclay in these immiscible blends. First of all, the dispersion and distribution of organoclay is investigated using XRD and TEM techniques. The organoclay is exfoliated and distributed in the dispersed PA6 phase as well as at the interface between PA6 and PP. Interestingly, more organoclay sheets are observed at the interface when the S2 or S3 blending sequences are utilized. From the SEM images, it is clear that the domain size of the PA6 phase decreases remarkably after introducing organoclay into the PP/PA6 blends. Two different rheological protocols are applied to probe the effect of organoclay on the morphology of the blend by in-situ monitoring the morphological evolution. The rheological results reveal that the phase morphology of the PP/PA6 blends remains relatively stable during shear for a wide range of shear rates when 1.0 wt% organoclay has been added. For the blends with a relatively high clay loading (5.0 wt%), a characteristic and pronounced “plateau” is observed in the low frequency range of the G′-ω curves, which indicates the presence of a percolating network of clay nanosheets. From the mechanical measurements, we find that the tensile strength of the blends increases slightly first and then declines dramatically with increasing organoclay content. Moreover, the elongation at break drops sharply as the organoclay content increases. In summary, it is clear that the organoclay can effectively reduce the domain size of the dispersed PA6 phase and stabilize the phase morphology in shear flow. However, the mechanical properties of the blends are not really improved by clay addition, even though a cocontinuous morphology with a percolated clay network was generated.