The author investigated a two-component pyrotechnical mixture used in the manufacture of delay detonators. Comparing the thermogravimetric, derivative thermogravimetric and differential thermal analysis curves of components with that of mixtures containing the components in different ratios, a relation has been found between the reaction rate and ratio. Initial temperature of reaction can be defined as well. Release of oxygen and oxidation takes place separately at certain temperatures and ratios. Mixture of highest rate of reaction generates the lowest heat of reaction.In the last twenty years delay detonators have been widely employed in blasting techniques to improve the efficiency of blastings [1, 2]. As delay elements usually pyrotechnical mixtures are used, containing combustible, oxidants, inhibitor and binding material [3,4]. Their speed of combustion can mostly be controlled empirically, by variation of the composition and grain size. Since the combustion time, delay effect and the reaction mechanism are closely related, it is hoped that the study of the latter during combustion will help in designing and adjusting the timing of delay detonators. The differential thermal analysis of pyrotechnical mixtures has been described [5][6][7]. If the behaviour of the components with increasing temperature is known, changes in the behaviour of mixtures indicate reactions among the components. When dealing with several components, it is necessary to investigate mixtures of various ratios of two, three, etc., components by means of the Derivatograph [8]. In the present paper it is intended to demonstrate this method on data referring to a mixture containing one oxidant and one combustible. ExperimentalThe tests have been carried out with a MOM Derivatograph using a ceramic specimen holder. Combustible: FeSi90 of technical grade (made by 13tv6zetgy~tr, Zagyvar6na, Hungary). Oxidant: MnO 2 of mineral grade (pyrolusite homogenized by AKZO, Amsterdam).

A two-component pyrotechnical mixture containing MnO 2 and PbuOl has been investigated by TG, DTG and DTA. It was found that under 48 ~ MnO 2 content the oxygen release exceeds the value calculated on the basis of the reactions MnO~ ~ Mn30~ and Pb30~ ~ PbO. Above a MnO~ content of 7.5 ~ the decomposition is partly delayed and shifted to higher temperatures. With under 60 % of MnO~, at about 700 ~ the components react exothermally with an increase in weight. The combined heats of the reactions MnO~--* Mn203 and Pb30~---r PbO give the highest value at 83 To of MnO~.The behaviour of the MnQ + FeSi 90 mixture was reported previously [1 ]. The investigation of the oxidant mixture MnO, + Pb304 is presented in this paper. ExperimentalOur tests had been carried out by a MOM Derivatograph using a ceramic sample holder. The components were MnO2 of mineral grade (pyrolusite homogenized by AKZO Amsterdam) and PbaO4 of technical grade 99~ purity (made by Metallochemia Budapest). The components were air dried. Grain size: > 60 pro.Weight of sample was 2000 • 5 mg in every case. The heating rate was 10~ The TG, DTA and DTG sensitivities were constant. The tests were carried out in air. The TG scale was marked by mg as the weight of" sample was constant. ResuLtsThe thermal decomposition of the pure Pb304 is presented in Fig. I. The thermal behaviour of MnO,, has been discussed in a previous paper [1 ].In the thermal treatment of Pb304, the following reaction takes place: Pb304 --* PbO indicated by the simultaneous change on DTA and DTG curve. The second DTA change indicates the melting of PbO. The temperatures of changes