Effect of Metal Oxide Nanoparticles on the Mechanical Properties and Tacticity of Poly(Methyl Methacrylate)
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1201-H05-18
Effect of Metal Oxide Nanoparticles on the Mechanical Properties and Tacticity of Poly(Methyl Methacrylate) Wantinee Viratyaporn and Richard Lehman Rutgers University, 607 Taylor Road, Piscataway, New Jersey, 08854-8065
Abstract Nanoparticles were incorporated into poly(methyl methacrylate) matrix by the mean of in situ bulk polymerization. Particle chemistry, size, shape, and percent loading were experimental variables in the synthesis and mechanical properties were assessed, particularly impact resistance, which showed improvement at the optimal particle loading. In assessing the mechanisms of this improvement, the elongated shape of zinc oxide particles appears to promote crack deflection processes to introduce a pull-out mechanism similar to that observed in fiber composite systems. Raman spectroscopy was performed to examine the effect of polymer chain conformation and configuration with the addition of nanoparticles. Introduction Polymer composites are useful in various applications from household goods to sophisticated electronic materials. In particulate/polymer composite systems, the polymerparticle surface interaction is a critical factor that influences the final properties of the polymer composites system.[1, 2, 3] The quality of the interaction determines to a significant extent the load-transfer efficiency and hence the mechanical properties.[4, 5] Naturally, this factor increases in significance as the size of the particles decreases, and the effect becomes dominant when the particles are at the nanometer scale. Nanoparticles have special effects on polymers since the particle size is of the same order as the polymer chain gyration.[6] Consequently, the nanoparticles can have a strong affect on the configuration and conformation of the surrounding polymer which leads to alterations in the bulk properties of the composite.[7, 8, 9] In this work, we sought to investigate this bound interfacial layer in nanoparticle/polymer composites using Raman spectroscopy and mechanical characterization. Our experimental system was comprised of aluminum oxide and zinc oxide nanoparticles in a PMMA matrix. Various particle sizes and volume fractions were chosen as experimental variables. The polymer nanocomposites were prepared by in situ bulk (radical) polymerization. To minimize the need for in-depth dispersion studies, nanoparticles pre-dispersed in propylene glycol methyl ether acetate were selected. Five combinations of nanoparticles types and sizes were used; two types of aluminum oxides (20 nm and 45 nm) and three types of zinc oxide (20 nm, 35 nm, and 70 nm). The aluminum oxide particles were spherical whereas the zinc oxide particles were acicular. With regard to mechanical behavior, electron microscopy images show that the nanoparticles in the PMMA lead to the debonding followed by a shear yielding mechanism
around the nanoparticles. Moreover, only at a specific particular volume fraction, unusually high (but reproducible) impact strength was observed, apparently resulting from debonding of t
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