DOI: 10.1002/prep.201300040 Experimental Diagnosis on Frictional Initiation of a Match Head Composition at Different Contact Materials Suthandathan Paramashivan Sivapirakasam,* [a] Mohamed Ismail Nalla Nalla Mohamed, [a] and Mahadevan Surianarayanan [b] 1 Introduction Accidental initiation by friction in the processing of match head composition due to different material contacts leads to fire and explosions. From the process safety point of view, the pace of initiation (i.e. initiation time) has to be evaluated to understand the initiation mechanism under frictional loading instead of the mere measurement of the friction sensitivity. Information relating the initiation phe- nomena of chemical mixtures to the materials and condi- tions are limited [1–5]. Hence, such a study dealing with the various materials becomes inevitable to avert accidents during manufacturing. In order to measure the pace of ini- tiation and hence to understand its mechanism under fric- tional loading, a well-designed test equipment is needed. Yet, frictional load slightly over threshold load (critical load) has been a credible route to violent detonation (the degree of violence) of energetic mixtures. Besides predict- ing the threshold load, an understanding of the effect of loads higher than the threshold limit, on the pace of initia- tion could give an insight on the mechanism of ignition and growth of reaction which are still poorly understood. With the modern data capture techniques such as optical microscopy, heat sensitive films [6], high-speed photogra- phy [7, 8] and oscilloscopic methods [9] the ignition mecha- nism caused by impact stimuli could be analyzed. Though these techniques had been used to measure the initiation caused by the impact stimuli, no work has been reported which examines the frictional initiation of energetic mix- tures using these data capture techniques. Visual evidence of ignition mechanism using high-speed photography is invaluable. However, optical photography can only observe in the order of a 0.1 mm length scale, which is much larger than the order of hotspots which typi- cally occurs between 0.1 and 10 mm [10]. Nevertheless the use of combined methods of optical microscopy, heat sen- sitive film, and high-speed photography to establish the ig- nition mechanism of energetic materials is highly expen- sive. The oscilloscopic method is found to be a simple ap- proach to get the information about the initiation of ener- getic mixtures under frictional load even at microsecond timing. The objective of this work was the experimental evalua- tion of the initiation mechanism of energetic mixtures like match head compositions under frictional loading. This has been investigated for the commonly used materials viz: steel Àsteel, aluminumÀ aluminum and brass À brass contacts by measuring the event of ignition and the critical load using a newly designed instrumental version of the BAM friction tester. The other objective was to study the influ- ence of load higher than the threshold frictional load on the degree of violence. A range of diagnostics and meas- urements of the critical load are the useful data suitable for understanding the initiation characteristics of the match head composition to enable safe manufacturing. Abstract : The mechanism of initiation is essential to enu- merate the sensitivity and evaluate the risks associated with energetic mixtures. To understand the mechanism of initiation under frictional loading, the initiation events such as initiating time and critical load have to be evaluated. This study aims to assess experimentally the initiation mechanism under frictional load by measuring the event of initiation and the critical load using a modified version of the BAM friction tester augmented with a press force sensor, an accelerometer and a photodiode arrangement. Differences in the range of diagnostics were identified for various material interactions. The data generated have the implications for assessing the safety of energetic mixtures. Keywords: Friction sensitivity · Initiation mechanism · Initiation time · Critical load · Process safety · Experimental diagnosis [a] S. P. Sivapirakasam, M. Nalla Mohamed Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli 620015, India *e-mail: spshivam@nitt.edu spsivam@yahoo.com [b] M. Surianarayanan Cell for Industrial Safety and Risk Analysis, Central Leather Research Institute, Adyar, Chennai-600020, India Propellants Explos. Pyrotech. 2013, 35, 1 – 8  2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim &1& These are not the final page numbers! ÞÞ Full Paper