Dagmar Merinska

Processing and Properties of Polyethylene/Montmorillonite Nanocomposites

Polyethylene (PE) nanocomposite samples were prepared with Cloisite 25 A, 30B, and 93 A and Nanofil 5 and 3000 nanofillers. The amount of modified Na+ montmorillonite (MMT Na+) was fixed to 5 wt%. For the compounding of PE matrix and nanofillers, two different compounding equipments were used, KO Kneader Buss and APV twin-screw extruder. In all samples, maleic anhydride-modified PE (PEMa) was added as a compatibilizer. The content of PEMa in mixtures was always 5 wt%. The level of MMT exfoliation in the nanocomposite systems was studied by X-ray diffraction and by transmission electron microscopy observations. The properties of samples were evaluated by dynamical mechanical analysis (E* modulus at 30°C) and by the measurement of tensile properties (stress and strain at break). Because of the possibility of usage of prepared materials in packaging industry, barrier properties were measured with focus on oxygen, carbon dioxide, and water vapor permeability. The influence of two different used compounding equipments on the prepared nanocomposite samples of PE nanocomposites was discussed.

Fire retardation of polystyrene/clay nanocomposites: Initial study on synergy effect

Polystyrene and its copolymers are a group of polymers with a wide field of applications. A major disadvantage among many of them is their high flammability. Previous research showed that one of the possibilities to reduce this negative property is to synergize conventional fire retardants and other types of fillers. Recent research showed that there is a synergy effect in clay-containing composites. This initial study is focused not only on the evaluation of synergy with modified or unmodified layered clay nanofillers but also on wide variety of other fillers such as clay nanotubes, melamine or magnesium hydroxide. All results are compared with pure polymer and polymer with conventional fire retardants. The samples were prepared in laboratory using Brabender Plasti-Corder kneader and analyzed by X-ray diffraction. Flammability was the most important property evaluated, and mechanical properties were also observed.

Ethylene-octene copolymers/organoclay nanocomposites: preparation and properties

Two ethylene-octene copolymers with 17 and 45 wt.% of octene (EOC-17 and EOC-45) were compared in nanocomposites with Cloisite 93A. EOC-45 nanocomposites have a higher elongation at break. Dynamical mechanical analysis (DMA) showed a decrease of tan δ with frequency for EOC-17 nanocomposites, but decrease is followed by an increase for EOC-45 nanocomposites; DMA showed also increased modulus for all nanocomposites compared to pure copolymers over a wide temperature range. Barrier properties were improved about 100% by addition of organoclay; they were better for EOC-17 nanocomposites due to higher crystallinity. X-ray diffraction (XRD) together with transmission electron microscopy (TEM) showed some intercalation for EOC-17 but much better dispersion for EOC-45 nanocomposites. Differential scanning calorimetry (DSC) showed increased crystallization temperature Tc for EOC-17 nanocomposite (aggregates acted as nucleation agents) but decrease Tc for EOC-45 nanocomposite together with greatly influenced melting peak. Accelerated UV aging showed smaller C=O peak for EOC-45 nanocomposites.