Composite Polymer for Hybrid Activity Protective Panel in Microwave Generation of Composite Polytetrafluoroethylene -Rapana Thomasiana

Abstract

During the microwave sintering of a polymer-ceramic composite plasma discharge is experienced. The discharge could occur failure of the power source. The solution proposed by the paper is original, no similar solutions being presented by the literature. It consists of using a polymer-ceramic composite protective panel, to stop the plasma discharge to the entrance of the guiding tunnel. Six composites resulted by combining three polymers, Polytetrafluoroethylene (PTFE), STRATITEX composite and Polyvinylchloride (PVC) with two natural ceramics containing calcium carbonate: Rapana Thomasiana (RT) sea-shells and beach sand were used to build the protective panel.Theoretical balance of the power to the panel was analysed and the thermal field was determined. It was applied heating using 0.6-1.2-1.8-2.4-3.0 kW microwave beam power. The panels were subjected to heating with and without material to be sintered. It was analyzed: RT chemical (CaCO3 as Calcite and Aragonite), burned area (range: 200–4000 mm2) and penetration (range: 1.6–5.5 mm), and thermal analysis of the burned areas comparing to the original data. PTFE-RT composite proved the lowest penetration to 0.6 and 1.2 kW. Other 1.2 kW all composites experienced vital failures. Transformation of the polymer matrix of composite consisted of slightly decreasing of the phase shifting temperature and of slightly increasing of the melting start and liquidus temperature.

Hydroxyapatite from Natural Sources for Medical Applications

“…To investigate the mechanical properties of the sintered specimens, all tests (compressive strength evaluation, micro-hardness measurement, and wear test) have been conducted in accordance with the international standards in force [ 39 , 40 ], but also based on our previous experience [ 41 , 42 ].…”

Microwave Technology Using Low Energy Concentrated Beam for Processing of Solid Waste Materials from Rapana thomasiana Seashells

“…In terms of optimization of the direct microwave heating process, the calculation of the minimum impedance of electrical circuit and maximization of transferred power from microwave generator to RT samples has led to the following balance power chart (see Figure 7a,b). The theoretical approach of the simulation of the thermal field started from the equations of heat transfer in solid materials [49,87].…”

“…The heating process was performed without RT samples placed inside the crucible and it was stopped when the crucible started to melt or the plasma arc occurred [86]. The theoretical approach of the simulation of the thermal field started from the equations of heat transfer in solid materials [49,87].…”

“…The main advantages of using RT are the very high CaCO 3 content (95-99% by weight) and the mechanical properties similar to hard tissues, such as human bones, and the low cost of production [48]. As a result, RT shells can be used as a natural source of calcium for the synthesis of biomaterials with applications in bone tissue engineering (TE) [49].…”

“…The research was oriented to obtain new products from RT seashells solid waste by applying two sintering technologies: the first technology was microwave sintering, consisting of direct microwave sintering and hybrid microwave sintering; the second technology was conventional sintering using an experimental oven with electrical resistance. In the case of powders obtained from domestic or natural solid residues based on RT seashells, according to the literature [49,85] they are susceptible to microwaves and can be heated for sintering, thus obtaining new products for biomedical applications and more. However, effects such as thermal runaway or the appearance of the microwave plasma arc, which can lead to the destruction of samples or even the microwave generator, often limit pure microwave sintering technology.…”