Kenneth E. Strawhecker

The synthetic routes and materials properties of polypropylene/montmorillonite nanocomposites are reviewed. The nanocomposite formation is achieved in two ways: either by using functionalized polypropylenes and common organo-montmorillonites, or by using neat/unmodified polypropylene and a semi-fluorinated organic modification for the silicates. All the hybrids can be formed by solventless melt-intercalation or extrusion, and the resulting polymer/inorganic structures are characterized by a coexistence of intercalated and exfoliated montmorillonite layers. Small additionstypically less than 6 wt %of these nanoscale inorganic fillers promote concurrently several of the polypropylene materials properties, including improved tensile characteristics, higher heat deflection temperature, retained optical clarity, high barrier properties, better scratch resistance, and increased flame retardancy.

Poly(vinyl alcohol)/sodium montmorillonite nanocomposites of various compositions were created by casting from a polymer/silicate water suspension. The composite structure study revealed a coexistence of exfoliated and intercalated MMT layers, especially for low and moderate silicate loadings. The inorganic layers promote a new crystalline phase different than the one of the respective neat PVA, characterized by higher melting temperature and a different crystal structure. This new crystal phase reflects on the composite materials properties. Namely, the hybrid polymer/silicate systems have mechanical, thermal, and water vapor transmission properties, which are superior to that of the neat polymer and its conventionally filled composites. For example, for a 5 wt % MMT exfoliated composite, the softening temperature increases by 25 °C and the Young's modulus triples with a decrease of only 20% in toughness, whereas there is also a 60% reduction in the water permeability. Furthermore, due to the nanoscale dispersion of filler, the nanocomposites retain their optical clarity.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTThe Critical Role of Solvent Evaporation on the Roughness of Spin-Cast Polymer FilmsKenneth E. Strawhecker, Sanat K. Kumar, Jack F. Douglas, and Alamgir KarimView Author Information Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 Polymers Division, National Institutes of Standards and Technology, Gaithersburg, Maryland 20899 Cite this: Macromolecules 2001, 34, 14, 4669–4672Publication Date (Web):June 6, 2001Publication History Received16 August 2000Revised15 February 2001Published online6 June 2001Published inissue 1 July 2001https://pubs.acs.org/doi/10.1021/ma001440dhttps://doi.org/10.1021/ma001440drapid-communicationACS PublicationsCopyright © 2001 American Chemical SocietyRequest reuse permissionsArticle Views4911Altmetric-Citations224LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Evaporation,Polymers,Quantum mechanics,Solvents,Surface roughness Get e-Alerts

The crystallization behavior of poly(ethylene oxide) (PEO) was studied in the presence of an inorganic filler surface (sodium montmorillonite) with DSC, as well as isothermal cross-polarization optical microscopy. Crystallization of PEO is found to be inhibited, exhibiting a decrease of spherulite growth rate and crystallization temperature. However, the overall crystallization rate increases with silicate loading as a result of extra nucleation sites, which occur in the bulk PEO matrix (i.e., far from the silicate surfaces). PEO differs from other systems, where crystallinity is typically enhanced next to such surfaces, in that the polymer is amorphized near the montmorillonite surfaces. This behavior is attributed to the specific way that PEO interacts with Na+ montmorillonite, where strong coordination of PEO to the surface Na+ cations promotes noncrystalline (ether crown) PEO conformations.