Initiation frictional

Impact and Friction Initiation of PETN have been extensively studied. This general subject is summarized in Bowden Yoffe (Refs 13 19), Afanas ev Bobolev (Ref 85a), and Vol 7, 135—55, which contains a rather complete description of impact initiation with many refs to the impact and friction initiation of PETN. There is general agreement that impact and friction initiation proceed via a hot spot mechanism (see Vol 7, HI 70—75). There is, however, considerable doubt and controversy about the mechanisms of hot spot formation... 

A 20 g sample, prepared and stored in a dry box for several months, developed a thin crust of oxidation/hydrolysis products. When the crust was disturbed, a violent explosion occurred, later estimated as equivalent to 230 g TNT. A weaker explosion was observed with potassium tetrahydroaluminate. The effect was attributed to superoxidation of traces of metallic potassium, and subsequent interaction of the hexahydroaluminate and superoxide after frictional initiation. Precautions advised include use of freshly prepared material, minimal storage in a dry diluent under an inert atmosphere and destruction of solid residues. Potassium hydrides and caesium hexahydroaluminate may behave similarly, as caesium also superoxidises in air. 

A violent reaction occurred when cleaning lump metal under carbon tetrachloride [1], Finely divided barium, slurried with trichlorotrifluoroethane, exploded during transfer owing to frictional initiation [2], Granular barium in contact with fluo-rotrichloromethane, carbon tetrachloride, 1,1,2-trichlorotrifluoroethane, tetrachloro-ethylene or trichloroethylene is suceptible to detonation [3]. Thermodynamic calculations indicated a heat of decomposition of 2.60 kJ/g of mixture and a likely adiabatic temperature approaching 3000°C, accompanied by a 30-fold increase in pressure [4],... 

See Other FRICTIONAL INITIATION INCIDENTS, METAL-HALOCARBON INCIDENTS Interhalogens... 

See other frictional initiation incidents See other HIGH-NITROGEN compounds, ANMETAL DERIVATIVES, TETRAZOLES... 

See other diazo compounds, frictional initiation incidents, glass... 

See related metal cyanides (and cyano complexes) See other frictional initiation INCIDENTS, MERCURY COMPOUNDS... 

See Other ACYL AZIDES, FRICTIONAL INITIATION INCIDENTS... 

Highly friction sensitive, with considerable explosion hazard [1], Repeating a published method ([2], where explosion at the m.p., 180°C is noted), the product was dried in a desiccator. When the lid (ground glass flange) was slid olf, the friction initiated explosion of a little of the compound deposited on the flange, and a severe explosion resulted [3],... 

The dry material is readily ignited, bums very rapidly and is moderately sensitive to heat, shock, friction or contact with combustible materials. When heated above its m.p. (103-105°C), instantaneous and explosive decomposition occurs without flame, but the decomposition products are flammable. If under confinement (or in large bulk), decomposition may be violently explosive [1], An explosion which occurred when a screw-capped bottle of the peroxide was opened was attributed to friction initiating a mixture of peroxide and organic dust in the cap threads [2], Waxed paper tubs are recommended to store this and other sensitive solids [3], Crystallisation of the peroxide from hot chloroform solution involves a high risk of explosion. Precipitation from cold chloroform solution by methanol is safer [4], Water- or plasticiser-containing pastes of dibenzoyl peroxide are much safer for industrial use. 

A pyrotechnic mixture containing the powdered ingredients was found dangerously sensitive to frictional initiation and highly explosive. 

See Aluminium, etc., Boron, etc. and Barium chromate, etc., all above See other frictional initiation incidents, static initiation incidents See also thermite reactions... 

The azide is very explosive, even when moist. Loosening the solid from filter paper caused frictional initiation. Explosion initiated by impact is very violent, and spontaneous explosion has also been recorded [1], It is also an exceptionally powerful initiator [2]. Detonation of the azide when dry has been confirmed [3], Good crystals are considerably more sensitive to shock, friction and electric discharge than is powder [4],... 

Mixtures with phosphorus explode on impact, and that with sulfur ignites on frictional initiation. 

A 14 kg batch of the mixture, mainly of boron and potassium nitrate, with a minority of the synthetic resin adhesive and solvent, exploded 5 min after blending had started. Several possibilities of a frictional initiation source were considered. 

Residues of potassium-sodium alloy in metal containers were covered with oil prior to later disposal. When a lid was removed later, a violent explosion occurred. This was attributed to frictional initiation of the mixture of potassium superoxide (formed on long standing of the alloy) and oil. 

Carbon impregnated with potassium iodide was used as an ozone-scrubbing filter in a chemiluminescence NO analyser. When the level of iodide was inadvertently increased to the high level of 40%, the filter exploded violently dining replacement after use. This was attributed to oxidation of iodide to iodate by ozone, and frictional initiation of the iodate-carbon mixture when the filter was dismantled. 

See FRICTIONAL INITIATION OF DUST CLOUDS See IGNITION SOURCES, THERMITE REACTIONS... 

FRICTIONAL IGNITION OF GASES AND VAPOURS FRICTIONAL INITIATION OF DUST CLOUDS GRAVEL... 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

See Nitric acid Glassware, Hydrogen peroxide, 5-Bromo-4-pyrimidinone See also CLEANING BATHS FOR GLASSWARE, FRICTIONAL INITIATION INCIDENTS... 

The work function of the rubbing surfaces and the electron affinity of additives are interconnected on the molecular level. This mechanism has been discussed in terms of tribopolymerization models as a general approach to boundary lubrication (Kajdas 1994, 2001). To evaluate the validity of the anion-radical mechanism, two metal systems were investigated, a hard steel ball on a softer steel plate and a hard ball on an aluminum plate. Both metal plates emit electrons under friction, but aluminum produced more exoelectrons than steel. With aluminum, the addition of 1% styrene to the hexadecane lubricating fluid reduced the wear volume of the plate by over 65%. This effect considerably predominates that of steel on steel. Friction initiates polymerization of styrene, and this polymer formation was proven. It was also found that lauryl methacrylate, diallyl phthalate, and vinyl acetate reduced wear in an aluminum pin-on-disc test by 60-80% (Kajdas 1994). 

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