Bitte wählen Sie ihr Lieferland und ihre Kundengruppe
The induction heating technique using particulate susceptors was successfully adapted for polymer-polymer composites. The heating is working on a contactless base due to its advantage to obtain the energy from an electromagnetic wave. It is intrinsic, locally applicable, and enables a precise temperature control which proved to be suitable for temperature sensitive composites. The studies included the investigation of material related variables, like susceptor material and fraction, as well as process related variables, like magnetic field strength and coupling distance. The heating was successfully achieved with ferromagnetic particles, cast iron and magnetite, at a filler fraction of a minimum of 5 wt-%. The electromagnetic field was driven with a frequency of 453 kHz at the maximum power level of 10 kW. By using these parameters, PA6 (polyamide) and HDPE (high density polyethylene) samples as well as the investigated self-reinforced polymer systems, HDPE/PP (polypropylene) and PP/PET (polyethyleneterephthalate), could be melted within three minutes. The fiber integrity was observed by means of microscopic and mechanical analysis and was not found to be significantly damaged during the heating process. On the one hand, cast iron was examined to deliver higher heating rates than competing magnetite particles. On the other hand, environmental studies have revealed a surface corrosion of iron particles. The corrosion does not decrease the heating ability and the matrix properties, but limits the applicability of the cast iron particles. In contrast, magnetite offers a higher applicability due to its impotence to corrode and to interact with other chemicals. In contrast, longer process cycles or higher susceptor fractions have to be accepted with magnetite. The expected selective character of a heat transfer by particles could only be validated to a certain extend. After the electromagnetic activation of particles, the thermal conduction was identified as one of the driving mechanism of particle induction. The particles heat the macroscopic sample in an intrinsic way, whereas on a microscopic scale, the heat transfer does not distinguish between reinforcement and matrix. As a consequence, reinforcement melting is theoretically also possible with particle induction but strongly depends on susceptor distribution. For spreading the induced heat mainly in the matrix, the matrix thermal conductivity had to be increased by the factor of 103, which was analytically investigated on the basis of the developed FEM (finite element method) model. Nevertheless, the necessary increase in thermal conductivity to homogenize the heating is not realizable in practice. The FEM model can moreover help potential customers to decide on the required amount of heating susceptors in future applications and to evaluate the time until the material processability is reached.