A Powder Processing Route to Polymer Composites
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1209-YY07-01
A Powder Processing Route to Polymer Composites
Giorgiana Giancola and Richard Lehman Department of Materials Science and Engineering, Rutgers University Piscataway, New Jersey 08854-8065 ABSTRACT Powder processing of thermoplastic polymer composites offers multiple advantages for both micro- and nano-scale systems. A high degree of component homogenization is achieved prior to melt forming of the composite, thus minimizing degradation associated with extended thermal processing at high shear. Polymer blends can be prepared that would otherwise not be possible due to thermodynamic incompatibility. Initial evaluation of this concept was conducted by processing PMMA and HDPE micron size powder prepared by emulsion polymerization. Spherical silica particles of comparable size (mean size = 5 µm) were added to a 30/60 PMMA/HDPE blend at the 10 volume percent concentration and mixed in an aqueous medium prior to drying and extrusion. Analysis of optical and electron microscope images of the raw mixture shows good homogeneity and distribution of the small inorganic particles around the larger matrix phase particles by the process of interstitial filling. The melt-processed composite was observed by SEM and consisted of a three-phase system of dispersed silica and PMMA particles in a HDPE matrix. INTRODUCTION Polymer/inorganic composites are multi-phase systems comprised of materials with varied chemical and physical properties. The combining of dissimilar materials for structural applications is aimed at achieving improved properties over any single material by generating ductility, specialized load transfer, and improved fracture behavior.[1-2] The morphological scale of composites is critical and the optimum size depends on the applications. Copolymer blends and interpenetrating polymer networks are examples of molecular level compositing. Particulate nanocomposites and certain fine-domain immiscible polymer blends are examples of coarser meso-scale composites. Commercial immiscible polymer blends and fiber composites are macro-scale composites with domain sizes greater than one micrometer. Immiscible polymer blends comprise a widely researched subject that focuses on novel materials with synergistic properties.[3] Mechanical properties can be enhanced by engineering the blend composition as well as the processing parameters.[3] The development of such materials is of special interest because this approach reduces the need to begin at the synthesis stage to develop new materials with specific properties.[4] Thus, blends prepared from FDAapproved polymers and with engineered domain sizes that are particularly suited to biological cell-growth requirements are of high value in biomedical applications such as tissue scaffolds and implant components. The addition of inorganic particulates is an attractive approach to producing polymer composites with a blend of organic and inorganic behaviors. A substantial body of work exists devoted to generating hybrid systems and also identifying effective methods for graft
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