Morphological Evaluation of PP/PS Blends Filled with Different Types of Clays by Nonlinear Rheological Analysis

Abstract

The effects of various Cloisite nanoparticulate clays with different hydrophobicities on (80/20) polypropylene/polystyrene (PP/PS) blends were investigated using their linear and nonlinear rheological properties. In descending order of hydrophobicity the four Cloisite clays examined were C20A > C10A > C30B > CNa+. Clays with a wetting coefficient ω a of between 1 and −1, that is C20A and C10A, located at PP/PS polymer interfaces and suppressed coalescence, while clays with a ω a of >1, that is C30B and CNa+, accumulated inside the PS droplets and increased viscosity ratios. As a result, C20A and C10A caused PS droplet size reductions while C30B and CNa+ did not change morphology of the PP/PS blend. Linear rheological properties as determined by SAOS (small amplitude oscillatory shear) test and nonlinear rheological properties determined by LAOS (large amplitude oscillatory shear) test revealed C20A and C10A increased mechanical properties of PP/PS blends. Rheological properties from SAOS and LAOS tests decreased in the same order as clay hydrophobicities at same concentration. The nonlinear–linear viscoelastic ratio (NLR is defined as normalized nonlinear viscoelastic properties/normalized linear viscoelastic properties) was used to quantify degrees of PS droplet dispersion and to determine the compatibilizing effects of the four clays on PP/PS blends. PP/PS blends filled with hydrophilic clays (C30B and CNa+) exhibited constant NLR values (NLR ≅ 1) with increasing clay concentration. However, NLR values of PP/PS blends containing C20A and C10A were much larger than 1 (NLR > 1) and increased with clay concentration, which concurred with reductions in droplet sizes. Interestingly, NLR values and droplet size changes exhibited inverse relationships with clay hydrophobicity. In addition, PS droplet sizes in PP/PS/C20A blends in the medium amplitude oscillatory shear (MAOS) flow region (Q 0 zone) were observed to check NLR validation. It was found that droplet sizes did not change in the MAOS region where NLR values are calculated and that thus NLR values corresponded with droplet sizes. Finally, inverse composition (20/80) PP/PS/C20A blends were studied, and a good correlation was obtained between PP droplet sizes and NLR values.

Characterization of polypropylene/polystyrene boehmite alumina nanocomposites: Impact of filler surface modification on the mechanical, thermal, and rheological properties

“…As a result, the rheological properties of the blend changed slightly, most likely because of the hydrodynamic (volumetric) effects of particles rather than them acting as morphology modifiers. Salehiyan et al . reported similar results when hydrophilic particles (Cloisite30B, untreated CNa + clays, and OX50 fumed silica) were added to 80/20 PP/PS blends: they mostly localized inside the PS droplets.…”

“…As a result, the rheological properties of the blend changed slightly, most likely because of the hydrodynamic (volumetric) effects of particles rather than them acting as morphology modifiers. Salehiyan et al 38,42,43 reported similar results when hydrophilic particles (Cloisite30B, untreated CNa 1 clays, and OX50 fumed silica) were added to 80/20 PP/PS blends: they mostly localized inside the PS droplets. In the case of BA80 OS2, particles went into both matrices in clusters and increased the viscosities of the polymers, that is, the viscosity ratios of the polymers may not have been disturbed enough to promote droplet breakup.…”

Morphology, thermal behavior, rheological, and mechanical properties of polypropylene/polystyrene blends based on elongation flow

“…In order to improve the properties of PP, a lot of inorganic fillers and rigid polymers have been used to prepare modified PP composites or blends 4‐7 . As a kind of rigid polymer, PS, with low cost, has been widely used for modifying PP to prepare PP/PS bends or its composites in recent years 8 . There are a lot of waste plastic products prepared from PP or PS every year.…”

“…Because very few molecular chains connect the two phases by traversing the interphase, the PP/PS blends usually result in serious phase separation with poor interfacial adhesion 11‐13 . Therefore, a lot of attempts have been carried out to improve the interfacial compatibility between the two phases of PP/PS blends 8,14‐21 . A number of compatibilizing agents have been applied to promote the adhesion between the PP and PS phases, such as PS‐ block ‐poly(ethylene‐butylene)‐ block ‐PS (SEBS) copolymers, 17 PP‐ g ‐PS graft copolymers, 18 and nanoparticles 8,19‐21 .…”

Influence of Nanoclay Localization on Structure–Property Relationships of Polylactide‐Based Biodegradable Blend Nanocomposites

“…It has been reported that clays can be used as a different class of compatibilizer, as they can stabilize the blend morphology more specifically when they are located at the interface between the two phases. In addition, they can prevent coalescence of the minor phase domains . Consequently, finer morphologies yield superior properties, as the domain phase is well distributed throughout the matrix.…”