The development of optimum formulations and the selection of proper foaming parameters to produce thermoplastics foams using chemical blowing agents is not trivial. Thus, it is necessary to develop techniques capable to provide reliable technical information about the "foamability" of a given system and scientific information about the mechanisms taking place. This work presents two novel techniques devoted to provide knowledge on the previous aspects. They are based on the analysis of a sequence of high resolution images (>5MPixels) acquired in-situ while the studied materials expand. For this purpose special furnaces -optical and X-ray transparent furnaces, respectively- have been built allowing for visualization the foaming process. In the case of optical expandometry the volume evolution versus time (or temperature) is obtained and therefore important technical information about the optimum composition parameters (type of polymer, blowing agent content, additives, etc) and the optimum foaming parameters (temperature and time) can be obtained considering the maximum expansion, expansion rate and the foam decay with time. On the other hand, X-ray radioscopy can provide similar results to those obtained by optical expandometry but, in addition, it allows for visualization of inner structure of the polymer foam during the expansion process allowing studying internal phenomena such pore coarsening, cell size evolution, and material distribution. These two special techniques are of a great potential to study in detail the foamability of thermoplastics although other polymeric foams such thermosets could be studied as well.
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