Evaluation of the effect of plasticizers on the DMA loss factor, the thermal and mechanical properties of Desmophen® 2200 based elastomers used for composite propellants
One of the main challenges concerning energetic materials regards the establishments and evaluations of new binders as alternative for the HTPB based composite rocket propellant formulations currently in use in the western countries. For this reason not only new energetic binders are considered (e.g the polyether Glycidyl Azide Polymer, GAP), but also new energetic components such as energetic plasticizers, which consist of low molar mass energetic polymers. Despite being inert, the polyester polyol Desmophen® 2200 (D2200®) has been investigated because of its good glass-rubber transition properties when mixed with polar energetic plasticizers. Also previous work has indicated that composite propellants based on Desmophen®2200 binder mixed with 35 mass-% TMETN as energetic plasticizer can give good ballistic performance properties compared to HTPB and GAP based formulations. But the strain capability and glass-rubber transition are still an issue to investigate. Thus, in the present work different pure binder were formulated and characterized. The aim was to evaluate the effect of changing the plasticizer type and its amount on the glass-rubber transition temperatures and mechanical properties of D2200® based binders. The polar binder D2200® was mixed individually with TMETN, Bu-NENA, BDNPF-A, GAP-A, EGBAA and TEGDA in amounts of 5, 20 and 35 mass-%, and cured with Desmodur® N3400. The cured elastomers were characterized using torsion DMA, tensile properties and thermal properties. The loss factor curves obtained by DMA were modelled with exponentially modified Gaussian (EMG) functions, and the effects of the plasticizer on the EMG parameters were evaluated. The description of the shift of the glass-rubber transition temperature with plasticizer concentration is undertaken.