Jacek Pigłowski

Crystallization in modified blends of polyamide and polypropylene

Abstract A modified polyamide 6 has been used as compatibilizer in blends of polyamide (PA) and isotactic polypropylene (PP). PA was modified in the molten state by trimellitic acid (TMA) and n -octyl glycidyl ether by reactive processing. NMR and FTIR results show that TMA and the ether reacted with PA. Isothermal crystallization kinetics of the polymers in neat and blend states has been investigated by differential scanning calorimetry. Crystallization behavior of the polymers in neat state differs from that in blends. However, tendencies are the same for the constituents. The rate of crystallization is highest in unmodified blends and lowest in neat polymers while intermediate in modified blends. An investigation of surface and interfacial tension revealed that both surface tension of modified PA and interfacial tension between modified PA and PP decrease as compared to unmodified PA. These results are consistent with optical micrographs that show finer dispersions of particles in modified than in unmodified systems.

Exfoliation of montmorillonite in protein solutions

In the study we demonstrate a method to obtain stable, exfoliated montmorillonite-protein complexes by adsorption of the proteins extracted from hen-egg albumen. Analysis of the process by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that the complexes are formed by sequential adsorption of ovotransferrin, ovalbumins, ovomucoid and lysozyme on the surface of the silicate. Structural studies performed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the adsorption of ovotransferrin and albumins is accompanied by disintegration of clay stacks into discrete platelets. Further analysis by dynamic light scattering (DLS) revealed that at protein to silicate weight ratios exceeding 20, the synergistic adsorption of albumen components leads to reaggregation of silicate platelets into disordered, microgel-like particles. By means of DLS it was found that exfoliation predominantly leads to formation of particles with average hydrodynamic radii (R(h)) of 0.19 μm while their aggregation causes formation of particles having R(h) in of approx. 0.5 μm and larger.

Comparative study on flame, thermal, and mechanical properties of HDPE/clay nanocomposites with MPP or APP

The article reports on flammability, thermal, and mechanical properties of bimodal high-density polyethylene/clay nanocomposites modified with ammonium polyphosphate or melamine polyphosphate (MPP) flame retardants. Two types of clays were used as fillers for the composites—the first one was standard montmorillonite modified with quaternary ammonium salt (ZR2), and the second one was montmorillonite modified with aluminium hydrogen sulfate (ZG1). As a compatibilizer, maleic grafted polyethylene (Plb) was used. X-ray diffraction and transmission electron microscopy were used to characterize the layer structure of clays in the composites. The limiting oxygen index tests showed synergistic effect between both clays and MPP. Flammability was also examined using cone calorimetry technique. The influence of all the fillers on thermal stability (thermogravimetric analysis), crystallinity (differential scanning calorimetry and wide angle X-ray scattering techniques), and mechanical properties was also studied.

Dynamic mechanical analysis of magnetorheological composites containing silica-coated carbonyl iron powder

This article describes the dynamic mechanical analysis of the behaviour of magnetorheological composites consisting of a magnetically active filler (carbonyl iron powder) and a soft thermoplastic elastomer matrix (styrene-ethylene-butylene-styrene). The carbonyl iron particle surface was coated by a sol–gel silica layer to improve the adhesion between hydrophilic magnetic particles and the hydrophobic polymer. Isotropic magnetorheological composites containing 81.25 wt% unmodified and silica-coated carbonyl iron powder were manufactured. The surface morphology of the carbonyl iron particles was observed using transmission electron microscopy, while its magnetic properties were analysed with a vibrating sample magnetometer. The magnetomechanical properties of the prepared magnetorheological composites were determined through shearing tests performed in various magnetic fields. The magnetorheological composites containing modified carbonyl iron powder have lower magnetorheological effect in comparison to the composites with pure carbonyl iron powder.

Phase dissolution in polymer blends Estimation of diffusion coefficients and the associated activation energy

SummaryIsothermal phase dissolution of regularly phase-separated structures at deep quench depths below the lower critical solution temperature was studied by light scattering technique for the blend of poly(styrene-co-acrylonitrile) and poly(methylmethacrylate). The phase dissolution studied in this work was that in the diffusion-controlled regime. During the process of phase dissolution the light scattering intensity decays exponentially with time at a rate depending on an effective diffusion coefficient for the center-of-mass motion of the chain molecules in the melt. The diffusion coefficient and the associated activation energy were estimated to be in the order of 10−14 cm2/s and 50 kJ/mol, respectively.

One-pot synthesis of PMMA/montmorillonite nanocomposites

Abstract This article describes simple preparation methods of poly(methyl methacrylate) (PMMA)/synthetic montmorillonite nanocomposites by single-step insitu polymerizations. Compatibility between PMMA and the silicate was ensured by an addition of (3-acrylamidepropyl) trimethylammonium chloride (AAPTMA). The work also compares how different synthetic routes, namely emulsion and solution polymerization, affect the structure as well as thermal and mechanical properties of obtained nanocomposites. The results of structural investigations clearly show, that both the techniques lead to intercalated nanocomposites, but emulsion polymerization allows more effective deflocculating and intercalating of the clay with acrylic copolymers. The addition of small amounts of layered silicates causes an increase in thermal stability and stiffness of the materials. It is demonstrated that at 5 wt. % of the filler, the temperature of 10 % weight loss was shifted up by nearly 50 K in comparison to the neat PMMA. In the same sample, the Young’s modulus of the material was found to be increased by 26 %.

Adsorption, aggregation, and desorption of proteins on smectite particles.

We report on adsorption of lysozyme (LYS), ovalbumin (OVA), or ovotransferrin (OVT) on particles of a synthetic smectite (synthetic layered aluminosilicate). In our approach we used atomic force microscopy (AFM) and quartz crystal microbalance (QCM) to study the protein-smectite systems in water solutions at pH ranging from 4 to 9. The AFM provided insights into the adhesion forces of protein molecules to the smectite particles, while the QCM measurements yielded information about the amounts of the adsorbed proteins, changes in their structure, and conditions of desorption. The binding of the proteins to the smectite surface was driven mainly by electrostatic interactions, and hence properties of the adsorbed layers were controlled by pH. At high pH values a change in orientation of the adsorbed LYS molecules and a collapse or desorption of OVA layer were observed. Lowering pH to the value ≤ 4 caused LYS to desorb and swelling the adsorbed OVA. The stability of OVT-smectite complexes was found the lowest. OVT revealed a tendency to desorb from the smectite surface at all investigated pH. The minimum desorption rate was observed at pH close to the isoelectric point of the protein, which suggests that nonspecific interactions between OVT and smectite particles significantly contribute to the stability of these complexes.

Structure and crystallization behaviour of poly(ε-caprolactone)/clay intercalated nanocomposites

Nanocomposites of poly(∊-caprolactone)/M-HTAB were obtained by polymerization of caprolactone with various amounts (10, 30, 50 and 64 weight ratio) of montmorillonite organophilized with hexadecyltrimethylammonium bromide (HTAB). The microstructure of nanocomposites was studied by small angle X-ray scattering (SAXS). Additionally, the melting enthalpies (ΔHm), the crystallinities and the half-time of isothermal crystallization were evaluated by differential scanning calorimetry (DSC). As a result of SAXS experiments for the composite PCL/M-HTAB 90/10, in the temperature range from 313 to 283 K, a rapid change in the interlamellar distance from 3.1 nm to 2.72 nm was observed. Similar scattering curves were obtained for the nanocomposite PCL/M-HTAB 70/30. In the composites containing 50% and 64% wt of M-HTAB, the decrease in interlayer distance was less pronounced in the same temperature range (d001 3.15 – 3.2 nm). DSC results clearly showed that the crystallization is divided into two separate processes: primary crystallization in the PCL matrix, and secondary crystallization.

Adhesion in polyamide/compatibilizer/polypropylene systems

Abstract The effect of compatibilization on the adhesion, fracture toughness, morphology, and mechanical properties of isotactic polypropylene (PP)/polyamide 6 (PA) blends was investigated. Maleic anhydride (MAH) functionalized poly-(ethylene-co-vinyl acetate) (EVA-g-MAH) and nonreactive EVA copolymer were used as compatibilizers in binary blends. An attempt of in situ compatibilization via addition of pure maleic anhydride to PA/EVA/PP melt was also made. The blends containing maleated EVA copolymer showed more regular and finer dispersion of phases, better adhesion at the interface, and improved mechanical properties.

Influence of carbonyl iron particle coating with silica on the properties of magnetorheological elastomers

In this paper, the influence of encapsulating carbonyl iron particles with various silica coatings on the properties of magnetorheological elastomers (MREs) was investigated. A soft styrene–ethylene–butylene–styrene thermoplastic elastomer was used as the composites polymer matrix. Spherical carbonyl iron powder (CIP) acted as the ferromagnetic filler. In order to improve the metal–polymer interaction, carbonyl iron particles were coated with two types of single and six types of double silica layers. The first layer was created through a TMOS or TEOS hydrolysis whereas the second one was composed of organosilanes. The mechanical properties of MREs containing 38.5 vol% of CIP were analysed under dynamic loading conditions. To investigate the magnetorheological effect in these composites, a 430 mT magnetic field, generated by an array of permanent magnets, was applied during testing. The results revealed that the magnetomechanical response of the MREs differs substantially, depending on the kind of particle coating.