Surface chemistry of a microcoated energetic material, pentaerythritoltetranitrate (PETN)

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Abstract
A microcoating technique was used to apply a polymer to an energetic explosive material. The explosive was pentaerythritoltetranitrate (PETN), and the coating was a copolymer consisting of vinylchloride/trifluorochloroethylene in a 1.5/1.0 molecular ratio. X‐ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to study the surface and interfacial chemistry of PETN powders and pellets made from compressed powders having either 0.5 or 20 wt% coating. Two simple models were used to discuss the nature of the copolymer film on the PETN. Model I shows the copolymer completely coating PETN; Model II depicts the copolymer as only partially covering PETN. Model II was applicable in explaining the 0.5 and 20 wt% microcoating of powders, as well as the 0.5 wt% coated pellets. However, the pellets with 20 wt% coating showed the copolymer to completely coat PETN (Model I), suggesting copolymer redistribution during pelletization. XPS and ISS results showed the copolymer film to be thin. An XPS expression modified to accommodate ISS data was developed for the calculation of the average copolymer thickness of PETN. The thicknesses were determined to be 10 Å and 6 Å for 0.5 wt% coated PETN powders and pellets, respectively. Bonding between the copolymer and PETN was concluded to be mechanical.