Primers, types

The particles therefore lose their charge. Since the charge provides the colloidal stability, the colloidal paint destabilises and deposits on the nearest surface, the car body. Primer coatings 12-35 /im thick are applied according to primer type. Each particle also contains a crosslinker for the resin, usually a blocked isocyanate. After rinsing, the primed article is passed into a hot... 

Types 1, 2, and 3 were selected for test with each of the primers, types A, B, and C. In addition, type 4 elastomer was used as a primer for types 1, 2, and 3. All elastomers types 1-6 were also tested without primers. 

Detailed analysis of the perimeter residue often yields useful information, for example, whether the bullet is unjacketed or jacketed and the nature of the jacket material. Primer type may occasionally be inferred and the presence of strontium or magnesium indicates a tracer or incendiary bullet, respectively. 

Type of ammunition—Jacketed bullets produce substantially fewer FDR particles than unjacketed bullets. Primer type (size, composition, burning characteristics) can influence the number of primer particles produced. The temperature and pressure achieved by the burning of the propellant determines the power and velocity of the bullet which can influence the number of particles deposited. 

At the start of 1978 the particle analysis method183 replaced the flameless atomic absorption bulk elemental method184 as the firearm residue detection method in the NIFSL. Since then the particle analysis method has been substantially improved by the use of a sample concentration/cleanup procedure,185 the addition of a backscattered electron detector, and the development of an automated residue detection system.186 187 Despite these improvements the technique remains costly and labor intensive. Certain aspects of the system required further work, in particular, the particle classification scheme discharge particles from mercury fulminate-primed ammunition and discharge particles from new primer types (Sintox). 

The interior of the spent cartridge case is routinely examined whenever FDR is detected on a suspect, to determine the type of primer involved in the incident. Figure 21.1 and Figure 21.2 illustrate primer types as determined by FAAS and SEM/EDX examination, respectively. 

A detailed summary of primer types encountered over a 13-year period (1975 to 1987) is given in Table 21.4 which represents the examination of 1,300 spent cartridge cases, involving 310 different head stamps and 58 manufacturers, and is based on casework results, some of which are included in Figure 21.1 and Figure 21.2 and Table 21.3. 

For category (c) mercury and barium would be absent and lead would be present. Modern type primers would be lead, antimony, barium, and lead, barium. On this basis a somewhat speculative breakdown of primer types involved in casework during this period is presented ... 

The nylon-coated bullets from Smith Wesson and the Geco TMJ bul-let/new primer composition, although effective in markedly reducing the lead levels, did not totally eliminate the problem. In 1983, Dynamit Nobel introduced 9 mmP caliber ammunition with a TMJ bullet and a primer free of lead, antimony, barium. The new primer type was called Sintox. A typical Sintox primer composition contains 15% diazodinitrophenol (DDNP) and 3% tetracene as the explosive ingredients, 50% zinc peroxide as the oxidizer, 5% of 40-pm size titanium metal powder, and 27% nitrocellulose as propellant powder.202 As expected, other munitions manufacturers eventually introduced similar ammunition, some with primers that were lead free but containing antimony and barium and others free of lead, antimony, and barium. The objective was to produce ammunition which performed satisfactorily in every way and did not produce any toxic product on discharge. 

Spark detonators have now been substituted by -> Bridgewire Detonators. If there is danger of stray currents, low-sensitivity primer types are employed, which can be actuated only by a strong current pulse. 

The resulting silicone-alkyd copolymers are thus formulated into coatings that have the same general and physical properties as alkyd resins and that can be applied in the usual manner. Silicone-alkyd copolymers generally require no special primer types. While there are numerous silicone intermediates that can be and are employed in the formation of organic-silicone copolymers, a few are shown (19) in Figure 1. 

Polyester primers are widely used in Western Europe. Although their corrosion resistance (salt spray test) is not as good as that of the other primer types, their mechanical properties are superior. 

Good adhesion of primers to metal substrates can best be achieved by ensuring cleanliness of the metal surface and by selection of generic coating primer types based on binders with chemical groups that can bond strongly to surfaces. 

Paint 20 Zinc-Rich Primers (Type I, Inorganic, and Type II, Organic)... 

Cutback asphalts comprise four types in the US (I-IV) and three types (I-III) in Canada. The No. I type consists of straight-run asphalt, and solvent and either a small amount of fiber or none the No. II type is obtained by adding a large amount of fibers and filler to the asphalt cut with solvent and No. Ill is primer-type in solution without any fillers or fibers. 

SGA of two-component types used in elevator structure SGA of main resin-primer type SGA of two-component type... 

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