The dispersion and polymer coating of ultrafine aluminum powders by the Ziegler Natta reaction

Abstract

Ultrafine aluminum powders have been identified as very promising fuels as part of energetic materials formulations. However, the large specific surface area that gives these powders a high reactivity also makes them particularly difficult to maintain in an unoxidized state. They also agglomerate easily during compounding processes. The coating of the particles by a polymer could offer a solution to these problems. We carried out the in-situ synthesis of high density polyethylene on the surface of aluminum nanoparticles by the Ziegler-Natta process. The process was found to be flexible enough to control the amount of polyethylene grafted on the powders. Ultrasounds were applied during the polymerization process to enhance the dispersion of the particles in the solvent. The resulting characteristics of the coated powders are discussed by means of thermogravimetric characterizations and electronic microscopy.

Poly(methyl methacrylate) as an Environmentally Responsive Capping Material for Aluminum Nanoparticles

“…There are a number of reports of the latter, which vary depending on whether oxide-passivated or oxide-free Al NPs are used. These include Ziegler–Natta polymerization of ethylene and propylene as well as di- tert -butyl peroxide-initiated free-radical polymerization of vinylidene fluoride. − UV light has also been shown to be an effective polymerization initiator toward the production of stabilized Al NPs . In this instance, the photopolymerization of methacrylic acid (MAA) was carried out on the Al NP surface in the presence of a diazonium salt.…”

Encapsulation of nanoparticles by polymerization compounding in a gas/solid fluidized bed reactor

“…In this approach, the particle surface becomes involved in the polymerization reaction so that a very intimate contact between the particle surface and polymer can be established bringing improved interfacial properties and, consequently, enhanced properties of the nanocomposite 5–7. In the last two decades, PC has been successfully applied to encapsulate different types of nanoparticles such as aluminum,8 aluminum oxide,9 zirconium oxide,10, 11 fumed silica,12 silicon carbide,13 and iron oxide14 and nearly all reported experimental investigations were performed in the liquid phase. The ubiquity of the slurry‐based process is easily explained.…”

“…Some drawbacks, however, arise when the process is carried out in liquid phase, as the polymerization reaction must be followed by additional steps to isolate the coated particles 8. After encapsulation, the reaction slurry must be filtered to separate the coated particles from the solvent.…”

“…An evident alternative to eliminate all the aforementioned negative aspects is to perform the nanoparticle encapsulation as a gas–solid reaction, where the gaseous phase contains the monomer of interest. The polymerization of ethylene via Ziegler–Natta catalyst for nanoparticle encapsulation and composite preparation has been reported by several researchers,8, 15, 16 using a liquid suspension where the ethylene gas is dissolved. We also have successfully used this procedure to encapsulate zirconia nanoparticles in hexane 11.…”

An evaluation of the solid hold‐up distribution in a fluidized bed of nanoparticles using radioactive densitometry and fibre optics

“…Polymerization compounding, also known as graft polymerization, is a well-known approach in the composite and nanocomposite preparation field. Hence, there are a number of studies concerning this approach (Salehi-Mobarakeh et al, 1997Rovira-Bru et al, 2001;Shi et al, 2001;Kasseh et al, 2003;Roy et al, 2004;Wang et al, 2005;Dubois et al, 2006). Recently, we successfully applied this technique to encapsulate zirconia nanoparticles with a thin layer of polyethylene in the order of a few nanometres (Esmaeili et al, 2006).…”