DMA of polyester-based polyurethane elastomers for composite rocket propellants containing different energetic plasticizers Maurı ´cio Ferrapontoff Lemos 1 • Manfred August Bohn 2 Received: 19 May 2016 / Accepted: 6 November 2016 / Published online: 16 November 2016 Ó Akade ´miai Kiado ´, Budapest, Hungary 2016 Abstract The aim of this work is to evaluate the effect of several types of plasticizers on the glass–rubber transition temperatures (T g ) of polyester-based polyurethane binders, using dynamic mechanical analysis (DMA). The polyester polyol commercially named Desmophen Ò 2200 (D2200 Ò ) has been investigated for use as binder for composite propellant applications due to its good ballistic properties and also due to its potential glass–rubber transition tem- perature when mixed with polar energetic plasticizers. Therefore, it is important to evaluate the behavior of D2200 Ò with different energetic plasticizers. In the present work, this inert polar binder was mixed individually with several different plasticizers and cured with a polyiso- cyanate commercially named Desmodur Ò N3400. The plasticizers used were: nitrate ester methyl trimethylol ethane trinitrate (TMETN), N-(n-butyl)-N-(2-nitroxyethyl) nitramine (Bu-NENA), bis-(2,2-dinitropropyl) formal and bis-(2,2-dinitropropyl) acetal mix 1:1 (BDNPF-A), nearly monodispersed low molar mass azido-terminated glycidyl azide polymer (GAP-A), ethylene glycol bis-(azidoacetate) (EGBAA) and 1,2-bis-(2-azidoethoxy) ethane (TEGDA) or BATEG, bis-azido-triethylene glycol, in an amount of 35 mass/%. The cured elastomers were characterized using torsion DMA at several frequencies, and the loss factor curves were described with exponentially modified Gaus- sian (EMG) distribution functions. Increasing deformation frequency in DMA increases T g , and an apparent activation energy was correlated with plasticizer performance. The plasticizer ability to decrease T g follows the order: TEG- DA [ butyl-NENA [ GAP-A [ EGBAA [ BDNPF-A [ TMETN. The ability of each energetic plasticizer could be related to its molecular structure, as well as to its molar mass and interaction possibilities with the polymer chains. Keywords Energetic plasticizer Á Desmophen Ò 2200 Á DMA Á Propellant Á EMG Introduction Currently, great effort is being spent on investigation and development of new energetic substances for binders of composite rocket propellants (CRP). The main interests are to increase energetic performance and allow non-toxic combustion with minimum formation of smoke [1]. How- ever, the insertion of energetic groups in elastomers often leads to poor mechanical properties at low temperatures. This is in general related to the reduction in chain mobility due to higher energetic interaction between elastomers molecules and chains by polar chemical groups [1–3]. At this point, the importance of plasticizers arises: increasing energy in the formulation, but avoiding these issues [4, 5]. D2200 Ò is a polyester polyol used in polyurethane for- mulations and has been investigated for application as a binder for CRP. Previous works have indicated that CRP based on this binder containing 35 mass/% of TMETN as energetic plasticizer (EP) can give good ballistic perfor- mance, but with still somewhat high T g [1, 6]. To be most effective in lowering the T g , a plasticizer may not contain adversely active chemical groups and should have low molar mass [7–12]. Intermolecular interactions should be low, although some are desirable to reduce loss of & Maurı ´cio Ferrapontoff Lemos engmlemos@gmail.com 1 Brazilian Navy Research Institute, Ipiru St. 2, Rio de Janeiro 21931-095, Brazil 2 Fraunhofer Institute for Chemical Technology, ICT, 76318 Pfinztal, Germany 123 J Therm Anal Calorim (2018) 131:595–600 https://doi.org/10.1007/s10973-016-5945-1