Influence of sample preparation and processing on observed glass transition temperatures of polymer nanocomposites

Abstract

Polymer composites composed of poly(methyl methacrylate) (PMMA) and silica (14 nm diameter) have been investigated. The influences of sample preparation and processing have been probed. Two types of sample preparation methods were investigated: (i) solution mixture of PMMA and silica in methyl ethyl ketone and (ii) in situ synthesis of PMMA in the presence of silica. After removing all solvent or monomer, as confirmed using thermogravimetric analysis, and after compression molding, drops in T g of 5-15 8C were observed for all composites (2-12% w/w silica) and even pure polymer reference samples. However, after additional annealing for 72 h at 140 8C, all previously observed drops in T g disappeared, and the intrinsic T g of bulk, pure PMMA was again observed. This is indicative of nonequilibrium trapped voids being present in the as-molded samples. Field-emission scanning electron microscopy was used to show well-dispersed particles, and dynamic mechanical analysis was used to probe the mechanical properties (i.e., storage modulus) of the fully equilibrated composites. Even though no equilibrium T g changes were observed, the addition of silica to the PMMA matrices was observed to improve the mechanical properties of the glassy polymer host.

Poly(propylene) composite with hybrid nanofiller: Dynamic properties

“…18 The opposite effect is explained by nonequilibrium state with excess free surface of voids. 19 In some cases, the glass transition has disappeared or polymer matrix has been nonsensitive on nanofillers. 20,21 The model presented by Lee et al 22 describes this phenomenon by a specific interaction between polymer and nanoparticles.…”

Interfacial effects on dielectric properties of ethylene propylene rubber–titania nano- and micro-composites

“…However, some studies have reported no change [11][12][13], and even some reduction [14][15][16], in the Tg of polymers as a result of filler loading. It has been noted that the nature of interactions between filler particles and the polymer matrix can both enhance and restrict the segmental motion of polymer chains, thus affecting the Tg of composites [10,17].…”

Recent advances in the modification of polyacrylate latexes

“…Thus, polyacrylate latex modified by inorganic nanoparticles, which is usually called polyacrylate/inorganic nanocomposite latex, can combine the advantages of both inorganic nanoparticles and polyacrylate. With regard to the fabrication of polyacrylate/inorganic nanocomposite latex, various inorganic nanoparticles, including montmorillonite [78,79], silica [80,81], calcium carbonate [82], zinc oxide [83], aluminum oxide [84], and titanium dioxide [85], have been reported.…”