Magnesium oxide, friction

FIGURE 26.4 Master curves on smooth, wavy glass, on a sihcon carbide track dusted with magnesium oxide and on a clean silicon carbide track of three acrylate-butadiene rubber (ABR) compounds as gum rubber, filled with 20 pphr carbon black and 50 pphr, respectively. (From Grosch, K.A., Sliding Friction and Abrasion of Rubbers, PhD thesis, University of London, London 1963.)... 

Presence of 5% of copper(II) chloride caused explosion to occur at 170°C [1]. Of the series of additives copper chromite, copper chloride, nickel oxide, iron oxide, magnesium oxide, the earlier members have the greatest effect in increasing the sensitivity of the perchlorate to heat, impact and friction. 

However, the pressure may be considerably reduced by the addition to the powder mass of substances such as graphite, or magnesium oxide, or both, that act as a lubricant by reducing the internal friction. The presence of graphite also diminishes... 

Dry mixtures of barium phosphinate and potassium chlorate burn rapidly with a feeble report if unconfined, but even under the slight confinement of enclosing in paper, a sharp explosion occurs. The mixture is readily initiated by sparks, impact or friction. A mixture of calcium phosphinate, potassium chlorate and quartz exploded during mixing. Mixtures of various phosphinates and chlorates have been proposed as explosives, but they are very sensitive to initiation by sparks, friction or shock. Admixture of powdered magnesium causes a brilliant flash on initiating the mixture. See Sodium phosphinate Oxidants... 

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