Lightweight Structural Foams by Foam Injection Moulding with Optimized Materials and Variotherm Moduls
This thesis focuses on the polymer processing technology "Foam injection moulding (FIM), with an emphasis on the description of the mechanical behaviour of injection moulded structural foams and on the development of a new processing method enabling the manufacturing of very lightweight structural foams not accessible with state of the art moulding technology. The aim is to describe and understand the correlation between the foaming conditions during foam injection moulding, the developed structural foam morphology and the mechanical properties of typical polypropylene materials. Further aim is the development of an manufacturing process enabling the production of very lightweight structural foams independent of their initial part thickness, to achieve very stiff integral structures at low mass per unit area.
The combination of vertical flash-face moulds with a variotherm cavity temperature device enables the effective control of the three important physical foaming parameters, as there are the pressure of the gas-laden melt, the degree of expansion of the cellular core as well as the temperature gradient of the polymer at the instant of foaming. Structural polypropylene foams produced by this process offer at a comparable thin part thickness a very high degree of expansion (density = 150 g/l) resulting in a high specific flexural stiffness (20-fold compared to compact polymer). These variotherm moulded structural foams possess a high capability for modern lightweight construction in transportation industry.
Furthermore, at a given final part thickness, maximisation of the compact skin layer thickness und reduction of the density of the cellular core must be aspired, to raise flexural stiffness and impact toughness. Finally, it can be stated, the level of the mechanical properties of structural foams is dominated by the relative amount of compact skin layers as well as by the total part thickness. The effect on mechanics of a homogeneous foam structure with an average cell size below 200 µm can be neglected.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Foam, polypropylene, structural foam, variotherm, foam injection moulding
Institute / chair: Fakultät für Angewandte Naturwissenschaften der Universität Bayreuth
Technical consultant for expert services: Prof. Dr.-Ing. Volker Altstädt (Betreuer), Prof. Dr.-Ing. Dietmar Drummer
Publication year: 2010
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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