Ge Organogermanium Compounds

Glockling, F.; Krüerke, Ulrich; Satgé, J.; Siebert, Christa

doi:10.1007/978-3-662-06324-8

Cited by 10 publications

(13 citation statements)

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“…For the phase-separable tougheners, both rubbers (e.g. carboxyl-terminated butadiene-acrylonitrile [9][10][11]) and thermoplastics (e.g. poly(ether sulfone) [12][13], poly(ether imide) [14] or polystyrene [15]) have been used.…”

Section: Introductionmentioning

confidence: 99%

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

et al. 2009

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The present paper investigates the effect of adding silica nanoparticles to an anhydride-cured epoxy polymer in bulk and when used as the matrix of carbon-and glass-fibre reinforced composites. The formation of 'hybrid' epoxy polymers, containing both silica nanoparticles and carboxyl-terminated butadiene-acrylonitrile (CTBN) rubber microparticles, is also discussed. The structure/property relationships are considered, with an emphasis on the toughness and the toughening mechanisms. The fracture energy of the bulk epoxy polymer was increased from 77 to 212 J/m 2 by the presence of 20 wt.% of silica nanoparticles. The observed toughening mechanisms that were operative were (a) plastic shear-yield bands, and (b) debonding of the matrix from the silica nanoparticles, followed by plastic void-growth of the epoxy. The largest increases in toughness observed were for the 'hybrid' materials. Here a maximum fracture energy of 965 J/m 2 was measured for a 'hybrid' epoxy polymer containing 9 wt.% and 15 wt.% of the rubber microparticles and silica nanoparticles, respectively. Most noteworthy was the observation that these increases in the toughness of the bulk polymers were found to be transferred to the fibre composites. Indeed, the interlaminar fracture energies for the fibre-composites materials were increased even further by a fibre-bridging toughening mechanism. The present work also extends an existing model to predict the toughening effect of the nanoparticles in a thermoset polymer. There was excellent agreement between the predictions and the experimental data for the epoxy containing the silica nanoparticles, and for epoxy polymers containing micrometre-sized glass particles. The latter, relatively large, glass particles were investigated to establish whether a 'nanoeffect', with respect to increasing the toughness of the epoxy bulk polymers, did indeed exist.

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Section: Introductionmentioning

confidence: 99%

The toughness of epoxy polymers and fibre composites modified with rubber microparticles and silica nanoparticles

et al. 2009

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“…[1][2][3][4][5], or a thermoplastic polymer, e.g. [6][7][8], into the epoxy can increase their toughness.…”

Section: Introductionmentioning

confidence: 99%

Toughening mechanisms of nanoparticle-modified epoxy polymers

Johnsen

Kinloch

Mohammed

et al. 2007

Polymer

850

576

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An epoxy resin, cured with an anhydride, has been modified by the addition of silica nanoparticles.The particles were introduced via a sol-gel technique which gave a very well dispersed phase of nanosilica particles which were about 20 nm in diameter. Atomic force and electron microscopy showed that the nanoparticles were well dispersed throughout the epoxy matrix. The glass transition temperature was unchanged by the addition of the nanoparticles, but both the modulus and toughness were increased. The measured modulus was compared to theoretical models, and good agreement was found. The fracture energy increased from 100 J/m 2 for the unmodified epoxy to 460 J/m 2 for the epoxy with 13 vol% of nanosilica. The fracture surfaces were inspected using scanning electron and atomic force microscopy, and the results were compared to various toughening mechanisms proposed in the literature. The toughening mechanisms of crack pinning, crack deflection and immobilised polymer were discounted. The microscopy showed evidence of debonding of the nanoparticles and subsequent plastic void growth. A theoretical model of plastic void growth was used to confirm that this mechanism was indeed most likely to be responsible for the increased toughness that was observed due to the addition of the nanoparticles. IntroductionEpoxy polymers are widely used for the matrices of fibre-reinforced composite materials and as adhesives. When cured, epoxies are amorphous and highly-crosslinked (i.e. thermosetting)polymers. This microstructure results in many useful properties for structural engineering applications, such as a high modulus and failure strength, low creep, and good performance at elevated temperatures.However, the structure of such thermosetting polymers also leads to a highly undesirable property in that they are relatively brittle materials, with a poor resistance to crack initiation and growth.Nevertheless, it has been well established for many years that the incorporation of a second microphase of a dispersed rubber, e.g. Hence rigid, inorganic particles have also been used, as these can increase the toughness without affecting the glass transition temperature of the epoxy. Here glass beads or ceramic (e.g. silica or alumina) particles with a diameter of between 4 and 100 μm are typically used, e.g. [9][10][11][12][13][14].However, these relatively large particles also significantly increase the viscosity of the resin, reducing the ease of processing. In addition, due to the size of these particles they are unsuitable for use with infusion processes for the production of fibre composites as they are strained out by the small gaps between the fibres.More recently, a new technology has emerged which holds promise for increasing the mechanical performance of such thermosetting polymers. This is via the addition of a nanophase structure in the polymer, where the nanophase consists of small rigid particles of silica [15][16][17][18]. Such nanoparticle-modified epoxies have been shown to not only increase further the toug...

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“…Indeed, the commonly-employed thermosetting epoxy matrices typically have a poor resistance to crack initiation and growth. Therefore, efforts have been made to improve the mechanical properties of the epoxy polymeric matrix, and thereby the properties of FRPs, through the incorporation of second-phase particles in the resin matrix [1][2][3][4][5][6][7][8]. The addition of micrometre-sized rubber particles [1][2][3] and, more recently, nano-sized silica (SiO 2 ) particles [4][5][6][7][8], into an epoxy polymer have been shown to improve the fracture energy of bulk epoxies by up to ten to fifteen times, without significantly impairing their other desirable engineering properties [5].…”

Section: Introductionmentioning

confidence: 99%