Dextrins modification

The introduction of LA into commercial detonators resulted in an unacceptably high level of explosions during manufacture and use and hence its use was discontinued until it could be prepared in less sensitive form. A number of methods have been used to prepare LA in a less sensitive form. The main control of properties is by synthesis rather than by any other approach. Lead azide compositions RD 1343 (improved CMC co-precipitated LA), RD 1352 (improved dextrinated LA) and Service lead azide (SLA) illustrate some modified LAs which are used depending on the requirements. Different processes developed for the modification of LA may be summarized as follows ... 

BRITISH GUM. — Artificial Gum—Torrefied Starch—Dextrin,—Under theso names a modification of stsroh Is known, which is often prepared in the following manner —... 

In comparative studies of starch fractions, Wilson, Schoch and Hudson, and also Kerr, - showed that the amylose fraction of starch gave much higher yields of Schardinger dextrins (up to about 70 %) than did the amylopectin fraction. Starch modification or degradation products in general gave reduced yields especially with beta amylase limit dextrins or acid hydrolyzed starch sirups there was no detectable production of crystalline dextrins. 

Although early workers had arrived at a hexasaccharide character for one modification of a-dextrin ( a-hexaamylose ) this result was of questionable significance because of the simultaneous findings that compounds now regarded merely as different crystalline modifications or complexes of a-dextrin were reported as a-diamylose, a-tetraamylose," a-octaamylose," a-amylosan, a-isoamylosan, and so on. If there was an element of truth here, it was well concealed by the surrounding confusion. 

The case of the a-dextrin represents an intermediate situation. Several different crystalline modifications , lu, ii4 crystallize in such a way that... 

The basic process has been documented in readily available sources [7,8], thus it will suffice to mention only the critical parameters for reference in comparing the more recent modifications to the processes and products. Dextrinated lead azide is made by adding over a period of 30 min a dilute (3%) solution of sodium azide to an equal volume of a 7% lead acetate solution, maintained at 60°C. The sodium azide solution, which contains an amount of potato dextrin roughly equal to 6% of the expected yield of lead azide, is made slightly alkaline with sodium hydroxide. The lead azide is thus formed mainly in the presence of excess dissolved lead salt and with a reasonably constant concentration of dextrin. The indir idual granules of dextrinated azide are formed by accretion in concentric layers of microcrystals bound with lead dextrinate (Figure 11). giving a product which is about 92% pure. 

Ch er the years numerous proprietary modifications have been made by private industry in order to improve the flow, pressing, and general handling and safety characteristics of dextrinated material. Figure 1 Id. for example, is a micrograph of a product known as Elcoat, manufactured by the duPont Company, which has 0.25% calcium stearate added as a coating to the dextrinated particles to decrease the sensitivity and improve the compactability of the powders. 

The air-dried dextrins were analyzed by established methods [11], except for absolute dextrin content, which was determined by a modification of the Munson-Walker method for determining reducing sugars [12]. In the determination of absolute dextrin, the described method was applied to the hydrolysate to... 

Animal gelatin can be used for crystal modification and desensitization of lead azide in a manner similar to dextrin. A product recently described by... 

The same authors " prepared copoly(vinyl alcohol-styrenesulfonic acid) resins which catalyze the hydrolysis of cubohydrates, among them dextrin and sucrose. Also, cation-exchanger membranes (from radiochemical grafting of styrene followed by reaction with chlorosulfonic add) were patented for the hydrolysis of dextrin to D-glucose. The results discussed may be useful for introducing subtle modifications into dextrins already prepared. A review on modified (converted) starches appeared in 1987. 

The uses of starch apply not only to the raw starches but to the endless variety of starch modifications achieved through gelatinization, wet and dry dextrinization, and derivatization (the formation of ethers and... 

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