Initiation by primers

Initiation by Booster. See below under Initiation, by Primers... 

Initiation (of Condensed Explosives) by Gas Detonations does not involve the same phenomena as Initiation by Primers or Boosters. The pressures generated in gas detonations are too low to produce sufficiently intense shocks in condensed explosives for shock phenomena to play a major role in the initiation of the latter. Even the energetic C2H2 + 02 detonation produces a detonation pressure of only ca 43 atm for an initial gas pressure of 1 atm. The max shock... 

Initiation by Primers (and Boosters) is the standard method of initiating secondary explosives. Thus hot wires (or other means) are used to initiate the primer charge (Lead Azide, Mercuric Fulminate etc) explosive whose detonation then initiates the main charge of PETN,... 

For a complete panel replacement, the refinisher starts with a panel preprimed in the appropriate stoving primer. For spot repairs or larger repairs without replacement of metal, there will be areas which have to be rubbed through to clean metal. Any indentations then have to be filled with a stopper or spray filler, probably based on unsaturated polyester resins and styrene, with cure initiated by mixing in an organic peroxide. After sanding, remaining bare metal areas are sprayed with a two-pack etch primer. 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

After the complementary strands are separated from each other, the primers attach themselves to the ends of the strands one primer becomes attached to one template strand, the other, to the complementary strand. Next, the enzyme causes bases to be added at the end of the primers, extending the formation of the complementary strands initiated by the... 

Tetryl is a pale yellow solid, melting at 129°C. It is moderately sensitive to initiation by friction or percussion. Tetryl is most used in the form of pressed pellets as primers for other less easily initiated explosives. 

Detonators are used to detonate high explosives. Stab detonators are initiated by sharp firing pins and are used in explosive trains of different types of fuses. Flash detonators are initiated by flames produced by safety fuses, primers, or delay elements. A special type of flash detonator ignited by the flame of a safety fuse is called a blasting cap. Detonators are primarily composed of three types of explosives including sinoxid mixtures, lead azide-based mixtures, and mercury fulminate-based mixtures. 

Tetryl (C7H5N508) is a pale yellow crystalline solid. It is moderately sensitive to initiation by friction and percussion and is used in the form of pressed pellets as primers for explosive compositions that are less sensitive to initiation. It is slightly more sensitive than picric acid and considerably more sensitive than TNT. In the early 1900s, tetryl was used as base charges for blasting caps but now has been replaced by PETN and RDX. During World War II, tetryl was used as a component of explosive mixtures. 

The lagging strand is synthesized discontinuously as a series of small fragments (about 1,000 nucleotides long) known as Okazaki fragments. Each Okazaki fragment is initiated by the synthesis of an RNA primer by primase, and then Completed by the synthesis of DNA using DNA polymerase III. Each fr ment is made in the 5 - 3 direction. 

In general, detonation of an explosive is initiated by a primer as a point-source. The detonation wave formed at the point-source propagates into the explosive in a spherical manner as shown in Fig. 9.1. 

If an atmosphere contg a combustible dust above lower limit is not completely confined, if might only burn when ignited by means of a flame or an electric spark, but it will detonate if in complete (or even pattial) confinement, especially if initiated by a detonator, primer, etc or when initiated by a blasting explosive such as takes place during mining operations... 

Igniters, which include devices called squibs, lighters and firing devices, etc are used for initiating expl or pyrotechnic compns whose nature is such that it is desirable to use flame or flash for their initiation and not a shock as produced by primers or detonators. 

Low-Explosive (LE). An explosive which when used in its normal manner deflagrates or burns rather than detonates that is the rate of advance of the reaction zone into the unreacted material is less than the velocity of sound in the unreacted material. LE s include propellants, certain primer mixtures, BkPdr, blasting explosives (See Ref 44, p B202-L), pyrotechnic compositions and delay compositions. Whether an explosive reacts as a high explosive or a low explosive depends on the manner in which it is initiated and confined. For example, a double base propellant when initiated in the usual manner acts as a LE. However, this material can be made to detonate if it is initiated by an intense shock. Conversely, a HE like TNT, can, under certain conditions be ignited by flame and will burn without detonation (Ref 40a, p 97)... 

A small-arms primer will not initiate, by itself, an expl chge (Ref 42, p 24)... 

When initiated by a nonexplosive impulse, the primer is part of detonator and this combination may be called primer-detonator... 

Fuze, Friction. A fuze initiated by pulling a toothed wire or plug thru friction-sensitive expl mixture in a fuze primer... 

Fuze, Hand Grenade. A pyrotechnic delay fuze initiated by release of a lever which in turn permits a striker to impinge on a primer. The output of the fuze is designed to ignite or detonate a filler of a hand grenade... 

Hangfire Primers. A hangfire in small arms ammunition (initiated by a blow from a firing pin) can be defined as that condition which exists when initiation of the usual chain of events following the release of the trigger in a loaded weapon, occurs at a rate slower than normal the definition of hangfire for electrically initiated ammo is similar... 

Uses Can be used in detonators when initiated by another primary expl and functioning as an intermediate booster or when mixed with another primary exp to increase the sensitivity of the latter to flame or heat. Its mixture with LA was patented by Dynamit AG (Ref 8) for use in explosive rivets. Tetracene can also be used in primer caps where as little as 2% in the compn results in improved uniformity of percussion sensitivity... 

Civil explosives are also known as commercial or blasting explosives and are typically used for mining, quarrying, construction and tunnel building. They are chemical compositions, which detonate when initiated by high explosive primers or boosters or directly by detonators. They are relatively insensitive to shock, friction or impact... 

A very important property of tetryl is its sensitiveness to initiation by a primer— hence its rapid rise in importance as an explosive for use in detonating caps, gains (boosters) etc. Martin [54] gives the following figures comparing the sensitiveness to initiation of tetryl and trinitrotoluene, under the influence of various primary explosives (Table 11). 

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