Thermal Stability: A Review of Methods and Interpretation of Data

Abstract

The assessment and understanding of thermal instability associated with process materials is a prerequisite for safe manufacturing. This is particularly true for materials exposed to elevated temperatures during processing. Information gathering on thermal stability should commence as early as possible in the process development lifecycle such that, initially, highly energetic substances can be identified and handled accordingly. Further studies to accurately define safe exposure temperatures should then be performed using equipment and methods specifically appropriate to the plant or processing technique selected, or envisaged, for scale-up. A simplified procedure for thermal stability assessment is proposed which takes into account decomposition and oxidation activity which are both commonly observed with organic substances. The strengths and weaknesses of individual test methods are reviewed, and information is provided on correct application of the resulting data.

On the Use of Differential Scanning Calorimetry for Thermal Hazard Assessment of New Chemistry: Avoiding Explosive Mistakes

“…Fora nalysing the thermallyinduced decomposition of potential energetic materials, sealed high-pressure (HP) rated crucibles are vital (Figure 4b;s ealed glass ampoules have been shown to be an alternative [18] ). [4,19,20] Hermetic (or crimped) aluminium crucibles are ubiquitous for other DSC measurements,s uch as phase transitions,a nd are used open, with ap ierced lid, or hermetically sealed with apress.T hese are inappropriate for hazard assessment however,a se ven when properly sealed they are incapable of withstanding much generated pressure and often rupture,c ausing as udden endotherm (Figure 3b).…”

Carbonization of methacrylonitrile and methacrylic acid copolymer with subsequent investigation of carbonized products

“…The cyano group peak at 2236 cm −1 is observed up to 750 • C. The carbondiimide peak -N=C=N-(2150 cm −1 ) disappears at temperatures above 350 • C. There are a number of peaks between 1690 and 1600 cm −1 which may indicate the presence of lactones, lactams, amines, pyridines, ketones, quinones and aromatic carboxyl groups. Most of these peaks disappear at 750 • C. Considering thermal stability, lactones, lactams and amines should be cleaved at the lowest temperature [17]. The absorbance due to the bending mode of the -OH group (1393 cm −1 ) is observed up to 600 • C. Two N-O absorbances are observed in the FT-IR spectra: N-O coupled with an aliphatic substituent at 1100-1000 cm −1 are seen in the spectra heated to 300-400 • C; N-O with an aromatic substituent exist from 300 to 750 • C.…”

Continuous Safety Improvements to Avoid Runaway Reactions: The Case of a Chloro-Thiadiazole Intermediate Synthesis toward Timolol

“…Based on the “100 K rule”, used for many years in the past, a rough estimation of the process safe temperature can be obtained. The rule consists in performing a dynamic DSC scan, determining the DSC onset, and subtracting 100 K (or less, according to the scan rate) from this temperature, obtaining the “safe temperature”.…”