Influences on the loss factor of elastomer binders and its modelling

摘要

The glass transition temperature of elastomer bonded composite rocket propellants and explosives is an important property determining their in-service application. It is defined as the main maximum of the loss factor (tanS). The loss factor as function of temperature is determined by DMA (dynamical mechanical analysis) measurements at some forced si-nusodial deformation at lower frequencies in the range of 0.01 to 100 Hz. With the term transition the center part of the molecular rearrangement process is meant, in which the transition from the energy elastic ('glassy elastic') to the entropy elastic ('rubbery elastic') behaviour, or vice versa, occurs. The loss factor of an elastomer binder is influenced by several factors: (1) filler type and content, (2) plasticiser type and content, (3) sterical hindrance, (4) interaction forces between all ingredients, (5) polymer chain conformation of the elastomer, (6) curing type and agent. Because the loss factor region of most elastomers filled with rigid particles consists of several sub-transitions, which can change differently during ageing, a special modelling of the loss factor curve is presented using so-named exponentially modified Gauss distributions. Therewith a separation of the molecular rearrangement regions or binder mobility fractions is achieved, after the application of a suitable baseline correction function to the loss factor curve.