The Use of the Specific Area in the Modelling of Sintering of Non-Spherical Polymer Particles
Fernando G. Torres, M. Cubillas, C. Aragon
POLYCOM - PUCP / Catholic University of Peru
PERU

Keywords: composites, sintering, modelling

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Polymer sintering has not been the subject of many studies in the past 50 years. For a long time the Frenkel-Eshelby model had been the only theoretical framework considered when analysing the sintering of polymer powders. That might have been due to the fact that polymer sintering did not find many industrial applications, but in the processing of highly viscous polymers, such as ultra high molecular weight polyethylene (UHMWPE) and polytetrafluorethylene (PTFE). With the development of rotational moulding as a common plastic parts manufacturing technique, the study of polymer sintering has gained some interest recently. Modifications of the original models have been proposed by several authors, considering the viscoelasticity of the materials and treating the sintering of two polymer particles as coalescence. However, the modelling of non-spherical particles has not been considered, in spite of the fact that in many rotomoulding applications the polymer powders show quite an irregular surface invalidating the "spherical-particle" assumption frequently used for modelling purposes.
In this paper we give a review of the existing approaches available for the modelling of polymer sintering. An original approach for the modelling of polymer sintering when non-spherical particles are involved is proposed. In the present study, the powders specific area is defined as a tensor. During the sintering process, the integral of that tensor over the whole domain decreases and tends to zero as full density is approached. Experimental techniques for the measurement of the specific area at different time intervals during sintering are also discussed.