Crystallization, mechanical, and fracture behaviors of spherical alumina‐filled polypropylene nanocomposites

Abstract

The objectives of this paper are to study the crystallization behavior and fracture characteristics of spherical alumina (Al2O3) nanoparticle‐filled polypropylene (PP) composites. Nanocomposites containing 1.5–5.0 wt % of the Al2O3 nanoparticles (pretreated with silane coupling agent) were prepared for this investigation. Wide angle X‐ray diffraction (WAXD) results show that a small amount of β‐crystal of PP forms after adding the Al2O3 nanoparticles. According to differential scanning calorimetric (DSC) and optical microscopy (OM) measurements, the Al2O3 nanoparticles make PP spherulite size reduced and crystallization temperature of PP enhanced, by acting as effective nucleating agents. However, there are no obvious differences in the crystallinity for the virgin PP and the Al2O3/PP nanocomposites. Tensile test shows that both the Young's modulus and the yield strength of the Al2O3/PP nanocomposites increase with the particle content increasing, suggesting that the interfacial interaction between the nanoparticles and PP matrix is relatively strong. Under quasi‐static loading rate, the fracture toughness (KIC) of the Al2O3/PP nanocomposites was found to be insensitive to nanoparticle content. Under impact loading rate, the Izod impact strength and the impact fracture toughness (Gc) indicate that the impact fracture toughness increases initially with the addition of 1.5 wt % of the Al2O3 nanofillers into the PP matrix. However, with the further addition of up to 3.0 and 5.0 wt % nanoparticles, both the Izod impact strength and impact Gc change very little. By observing the single‐edge‐double‐notch (SEDN) specimens with optical microscopy after four point bending (4PB) tests, it was found that numerous crazes and microcracks form around the subcritical crack tip, indicating that crazing and microcracking are the dominant fracture mechanisms. Scanning electron microscopy (SEM) observation confirms this result. In addition, when the strain rate of 4PB tests was increased, some wave‐like branches were formed along the fractured edge for the Al2O3/PP nanocomposites. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3652–3664, 2005

Mechanical and Morphological Properties of Polypropylene/Nanoα-Al2O3Composites

“…High magnification TEM micrographs of PP/1% α -Al 2 O 3 nanocomposites show that the nano α -Al 2 O 3 particles are close to spherical shape; although their sizes are not monodisperse, particles between the size of 27 and 35 nm are detected in the nanocomposite. These results are in good agreement with the Bikiaris et al [16] and Zhao and Li [6] findings, in which the rise in the nano α -Al 2 O 3 particles loading causes a little poorer dispersion of the nanoparticles but more agglomeration.…”

“…Polymeric nanocomposites that possess increased stiffness and ductility with having a reasonably low loading of nanofillers were reported [3]. The enhancements are normally established by a few factors, such as the inherent features of nanofillers and polymers, the interface and the interphase among the constituent components, and dispersion of nanofillers in the matrix [6]. Nanocomposites produced using either organic or inorganic nanofillers have been the main focus of numerous researches in current years as they generally not only dwell in the merged properties of organic polymers (e.g., elasticity, ductility, and dielectric) and inorganic materials (e.g., high thermal permanence, strength, hardness, and high refractive catalog), but also they may obtain some particular or new properties.…”

Nonisothermal melt crystallization kinetics of syndiotactic polypropylene/alumina nanocomposites

“…Both organic layered silicates and silver nanoparticles significantly increased the crystallization rate of sPP owing to their heterogeneous nucleation effect 15, 16. Alumina nanoparticles were reported as very effective nucleating agents and improved tensile and impact properties of isotactic polypropylene 17…”

Polypropylene Nanocomposites Based on Synthetic Organic-Soluble Ag Nanocrystals with Prominent β-nucleating Effect: Quiescent Crystallization and Melting Behavior

“…[17] Generally speaking, most β-nucleating agents of iPP are crystallizable organic compounds with low molecular weight. However, there are also a few literature reports about inorganic particles acting as β-nucleating agents, such as CaCO 3 , [18] Al 2 O 3 , [19] wollastonite, [20] talc, [21] glass beads, [22] etc. However, to the best of our knowledge, there are few references found in open literatures about Ag nanocrystals (NCs) inducing the formation of large amounts of β-crystals in iPP.…”