Paper caps

Russia and other counrries it. has been used for prepn of "snaps", "pull-crackers", paper caps for toy pistols and "jumpiog frogs". Also in amusement devices such as "cigars" and "spiders". If a few grains of wet SF are spread on a floor, loud cracks are heard if they are walked upon (See Beil 1, 722 and AddnlRefs for SF)... 

Rockets of the smaller sizes, for use as toys, are closed at the top with plugs of solid clay and are supplied with conical paper caps. They produce the spectacle only of a trail of sparks streaking skyward. Rockets are generally equipped with sticks to give them balance and direct their flight and are then fired from a trough or frame, but other rockets have recently come on the market which are equipped with vanes and are fired from a level surface while standing in a vertical position. 

The so-called Japanese torpedoes appear to be an American invention. They contain a paper cap placed between two masses of gravel, and in general require to be thrown somewhat harder than silver torpedoes to make them explode. The same torpedo board is used as in the manufacture of silver torpedoes, but a gravel board which holds only about half as much gravel. After the gravel has been put in the paper cups, a paper cap, still moist, is placed on top of it, more gravel, substantially equal in amount to that already in the cup, is added to each, and the tops are twisted. 

Muffler pipe for samples producing loud noises (like sporting paper cap, PETN, RDX, HMX, and primary explosives) shown in Figure 3.9. 

Figure 3.11 The accumulated explosion rate plotted on semi—log paper in normal and logarithm scale with Sporting Paper Cap.

CMC-Silver azide Black Powder Picric acid(coarse) Picric acid(fine) Trinitrotoluene (TNT) Nitroguanidine Guanidine nitrate m-Dinitrobenzene Others Dibenzoylperoxide Sporting paper cap Flat paper cap DPT" ... 

Figure 3.11 shows the distribution of the accumulated explosion ratio frequencies for a drop ball test using sport paper caps 2 4 . Test trials at each fall height are done 30 times (a) is the case where the fall heights are taken at the same interval and (b)is the case where the logarithms of the fall heights are taken at the same interval. Apparently the case where log H is taken with the same intervals shows better linearity and is nearer to a normal distribution. 

The next problem is to determine an adequate up and down interval.Dixon indicated that the interval near a is adequate and should be in the range of 0.5-2.0 o 2 n. The impact sensitivity of the sport paper caps had a narrow deviation range, and it was observed that the distribution was nearer to a normal logarithmic distribution. However, common explosive substances do not always behave this way. Figure 3.12 shows an example. 

Some substances make a loud sound upon exploding and others hardly make a sound in drop ball impact sensitivity tests. The simple contact mixture of potassium chlorate and red phosphorus is one of the substances which makes loud sound when exploding. About a lOOdB (A-fast) noise is measured at a distance of 3m. The frequency distribution is shown in Figure 3.19 J 21. However the mixture does not always make the same explosive sound sometimes it makes softer sound, and other times, no sound at all. Sporting paper caps and toy paper caps cause loud noises with narrow frequency... 

The commercial products, sporting paper caps (SPC potassium chlorate, red phosphorus and sulfur), toy paper caps (same components as SPC) and silver azide cartridges for breaking renal calculi have lower sensitivity than their powdery components because they are packaged as cartridges. 

The sporting paper caps which are used for starting signal pistols in Japan each contain about 0.05 g of a composition consisting of 74% potassium chlorate, 18% red phosphorus, 8% sulphur and small amount of starch. Recently, the hazard classification on the packaging of these paper caps for transportation on ships was discussed. 

The commercial products of RADIE Co. Ltd. (trade name EVERNEW) were used as the sampls of sporting paper caps. Fig.5.1 and Fig.5.2 show the structures, cases and packages of the sporting paper caps. 

Fig. 5.3 MKm ballistic mortar into which a sheet of paper cap was inserted...

The explosive power of 100 sporting paper caps (about 5 g of explosive)was measured by use of MKIII ballistic mortar initiated by a No.6 detonator as shown in Fig.5.3. 

The length of the ballistic pendulum swing from the explosion of 100 sporting paper caps and one No. 6 detonator is 165 mm. That from only one No.6 detonator is 30 mm, so the net result from 100 sporting paper caps is 135 mm. In comparison with a 151 mm swing from 5 g of TNT, the explosion power of the sporting paper caps is 89% of that of TNT. 

The test results are shown in Table 5.1. B is the relative power to TNT. Even if the length of gap is increased up to 110 mm, the paper caps explode, so we cannot determine the length of gap in which the paper caps do not explode. It is known that for some substances with logE r, o = -1.34 in drop ball test, they cannot be measured in the small gap test. 

Table 5.1 The test results of sporting paper caps in small gap test by use of MKIII ballistic mortar...

Adhesive tape Paper caps(10) Glass lube No. 0 detonator... 

Fig. 5.4 Set-up for gap test using MKHI ballistic mortar and paper caps...

Table 5.3 The results of small gap test(II) of sporting paper caps...

Table 5.4 test results for the sympathetic explosionof sporting paper caps inside small cases... 

The UN pressure vessel test was applied to one sheet of sporting paper caps (about 5 g of explosive). The bursting pressure of the rupture disk was 5.9 kg/cm 2, and the average rate of temperature rise was 30 °C /min. 

The test results are shown in Table 5.5. Because the paper caps are well-sealed they decompose violently when heated. 

A package of five large cases containing sporting paper caps was placed in a hole in the ground,and the stack test was carried out similarily to the single package test. 

To observe the burning situation of sporting paper caps, one begins with a burning test one a larg case containing 3000 caps. 

The large case was burned for 5 minutes a violent combustion was not observed. The combustion was similar to the slow combustion of paper caps. 

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