title: A simple method to improve the clarity and rheological properties of polymer/clay nanocomposites by using fractionated clay particles.
abstract: We present a simple method to improve the transparency and rheological properties of polystyrene/organoclay nanocomposites. Such composites are typically prepared using organophilic derivatives of commercial montmorillonite (MMT) clays that contain a wide range of particle sizes. Our approach is to fractionate the native MMT clay to exclude large aggregates and then modify the fractionated clay (FMT) by a surfactant treatment (the resulting organoclay is termed o-FMT). Polystyrene nanocomposites made from the o-FMT are then compared with those made from a commercial organoclay having the same surfactant treatment. The o-FMT-based composites exhibit much better rheological properties (e.g., their elastic moduli at low frequencies are approximately 10 times higher) at equivalent mass loadings. Moreover, the o-FMT-based materials also have better transparency: e.g., a 10% o-FMT sample transmits as much light as a sample with 5% commercial clay. Transmission electron microscopy confirms that these differences in properties are related to microstructural differences; i.e., large aggregates are generally absent in the o-FMT samples. Clay fractionation may thus be a general strategy to enhance the properties of polymer/clay nanocomposites.
authors.affiliation: Department of Chemical & Biomolecular Engineering, University of Maryland, College Park, Maryland 20742-2111, USA.
authors.forename: Bani H
authors.initials: BH
authors.lastname: Cipriano
authors.forename: Takashi
authors.initials: T
authors.lastname: Kashiwagi
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.forename: Srinivasa R
authors.initials: SR
authors.lastname: Raghavan
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry*; D000077215:Clay; D005782:Gels / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D011108:Polymers; D012212:Rheology / Q000379:methods*; D013053:Spectrophotometry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D005782:Gels; D011108:Polymers; D014867:Water; D001546:Bentonite; D000077215:Clay