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The effect of various fillers on the mechanical, barrier, and flammability properties of polypropylene (PP) was studied. PP was filled with 4 wt% of nano-sized calcium carbonate, titanium dioxide, organoclay, and multiwalled carbon nanotube (MWCNT). For comparison, micron-sized calcium carbonate was also studied. Two-step masterbatch dilution approach of the composites suggested no or only minor improvements in Young's modulus and tensile yield strength, whereas their ductility decreased compared to coupling agent-modified PP matrix. The water vapor transmission results of filled films showed increased permeability compared to their coupling agent-modified counterpart. Oxygen permeability, however, decreased for the composites. The MWCNT-filled matrix showed the highest barrier and fire performance, attributed mainly to its higher filler volume content, but also other reasons such as the effect of filler dispersion, composite's thermal stability, and polymer crystallinity were discussed.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

The morphological, mechanical, thermal, and tribological properties of high-density polyethylene (HDPE) composites reinforced with organo-modified nanoclay (3 and 6 wt%) were studied. A commercial maleic anhydride-based polymeric compatibilizer (PEgMA) was used to improve the adhesion between the polyethylene and clay. Transmission electron microscopy (TEM) characterization of composites revealed that nanoclay exists mainly in a multilayered structure in the HDPE matrix. Mechanical testing of composites showed that Young's modulus and tensile strength increased with nanoclay content. Coefficients of the linear thermal expansion (CLTE) of HDPE–PEgMA–clay composites were slightly lower in the flow direction than those of HDPE–PEgMA. The tribological properties were measured in dry conditions against a steel counterface. The friction coefficient of the matrix was decreased by the addition of clay. Electron microscopic results suggested that the wear mechanism for HDPE and HDPE composites was mainly adhesive. Clay agglomerates were observed on the worn surfaces of the composites, which may partly explain decreased friction. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

Polyamide and polystyrene particles were coated with titanium dioxide films by atomic layer deposition (ALD) and then melt-compounded to form polymer nanocomposites. The rheological properties of the ALD-created nanocomposite materials were characterized with a melt flow indexer, a melt flow spiral mould, and a rotational rheometer. The results suggest that the melt flow properties of polyamide nanocomposites were markedly better than those of pure polyamide and polystyrene nanocomposites. Such behavior was shown to originate in an uncontrollable decrease in the polyamide molecular weight, likely affected by a high thin-film impurity content, as shown in gel permeation chromatography (GPC) and scanning electron microscope (SEM) equipped with an energy-dispersive spectrometer. Transmission electron microscope image showed that a thin film grew on both studied polymer particles, and that subsequent melt-compounding was successful, producing well dispersed ribbon-like titanium dioxide with the titanium dioxide filler content ranging from 0.06 to 1.12wt%. Even though we used nanofillers with a high aspect ratio, they had only a minor effect on the tensile and flexural properties of the polystyrene nanocomposites. The mechanical behavior of polyamide nanocomposites was more complex because of the molecular weight degradation. Our approach here to form polymeric nanocomposites is one way to tailor ceramic nanofillers and form homogenous polymer nanocomposites with minimal work-related risks in handling powder form nanofillers. However, further research is needed to gauge the commercial potential of ALD-created nanocomposite materials.

The effects of adhesion promoter properties on the structure and mechanical behavior of nanoclay-filled polyolefin nanocomposites are presented. Two different maleic anhydride-modified polypropylenes having varying maleic anhydride content and molecular weight were used. The influence of these parameters on the performance and morphology of the prepared polypropylene and high density polyethylene-based nanocomposites was examined by mechanical testing, X-ray diffraction, and electron microscopy. The low molecular weight adhesion promoter seemed to be effective in both matrices in relation to mechanical property enhancements, whereas its high molecular weight counterpart performed well only in polyethylene matrix. X-ray diffraction results and examination of morphology revealed that the intercalation and the dispersion of the nanoclay were more even in both matrices when the low molecular weight adhesion promoter with a higher maleic anhydride content was used. On the other hand, the use of high molecular weight adhesion promoter led to a less uniform dispersion but also to a greater amount of exfoliated clay particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The differences that direct melt compounding and masterbatch dilution cause in the properties of melt compounded polypropylene (PP) and high density polyethylene-based (PE-HD) nanocomposites are presented. The results include comparison of properties and morphology of directly melt processed organoclay nanocomposites with similar compounds diluted from commercial and in-house-made masterbatches to clay concentrations of 1, 3, 6, and 8 wt%. The compounds were prepared with a co-rotating Brabender twin-screw extruder. The degree of exfoliation and the dispersion of the nanoclay were verified with transmission electron microscopy and X-ray diffraction. Thermal stability of the materials was examined with thermogravimetric analysis and the mechanical properties of the compounded materials were also determined. The most promising results regarding mechanical behavior were achieved with the in-house-made masterbatch in the form of a notable increase in Young's modulus in both matrices. There was also a distinct increase in impact strength when masterbatch was used. Changes were more pronounced in case of PP. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

Polycarbonate nanocomposites were prepared by melt processing from two surface-modified montmorillonite organoclays. The intercalation spacing and degree of the dispersion were characterized with wide-angle X-ray diffraction and transmission electron microscopy, respectively. The polycarbonate nancomposites showed rather good dispersion of nanoclay, with a mixture of exfoliated, intercalated, and confined morphology. The effect of nanoclay on the mechanical response of specimens subjected to tensile and impact loading was investigated. Results demonstrated that nanocomposites based on nanoclay possess increased Young's modulus and yield strength. However, their ductility upon tensile loading is significantly affected. A transition from ductile to brittle deformation occurs at studied clay loadings. Notched impact strength experiments supported this, showing that impact strength decreases significantly as nanoclay content increases from 1 to 5 wt%, regardless how the nanoclay surface was modified. Thermal analysis demonstrated that addition of nanoclay leads to decreased thermal stability of polycarbonate suggesting, enhanced dynamics of polymer chains. Finally, the tribological properties of selected specimens were evaluated using a pin-on-disc, and the effect of nanoclay fillers on tribological properties is discussed.