Papers by Keyword: Microwave Curing

Abstract: Process time reduction and energy/cost savings are usually in the focus of production process improvements. New technologies provide possibilities to achieve significant enhancements for relevant operation figures.Curing cycle times for CFRP manufacturing depend on several requirements: Type of resin, requested glass transition temperature, used equipment and energy source as well as sample size, weight, fibre volume ratio, fibre orientation etc. Conventional methods are mostly based on heat conduction while microwaves offer a selective and volumetric heating of the samples. Process time reduction and energy saving are the positive effects of the microwave curing technology.This paper will give an overview of the current status of this process technology not only focussing on technical aspects but also covering the process and economic effects.This work has been performed under the German BMBF project 02PJ2131, FLAME under the program Energy Efficient Light Weight Construction.

Abstract: Temperature monitoring was done on microwave curing of epoxy resin system consisting of di-glycidyl ether of bisphenol-A(DGEBA) E-51 and curing agent 4,4’diamino-diphenyl-methane (DDM). The study shows that microwave curing of epoxy resin system is an exothermic reaction and the temperature variation during microwave processing has the obvious characteristics of “temperature increment - heat release - temperature falling”. Analysis on the infrared thermal images indicates that each moulding body has its own temperature distribution and differs from others. The non-uniform temperature distribution reveals the uneven electric field distribution in the domestic microwave oven.

Abstract: This paper presents a feasibility of microwave curing for SiO₂/UPR composites. Experimental results show that the curing time by microwave curing is shorter than that of heat curing. Compared with the heat cured samples, the mechanical properties and infrared structure of the samples cured by microwave is constant. Research shows that microwave curing is efficient that for SiO₂/UPR composites.

Abstract: In this present work attempts have been made to study the difference between microwave heating and conventional thermal heating in curing the epoxy-amine system of di-glycidyl ether bisphenol-A(DGEBA) with the curing agent of 4,4′Diamino diphenyl methane(DDM). Curing behaviors and mechanical properties of the system were studied through a number of experiments. Differential scanning calorimetry (DSC) technique was implemented to measure the glass transition temperature and kinetic parameters, and fourier transform infrared spectroscopy(FT-IR) was used to analyse the cure reaction mechanism of the resin system. Finally, microstructure of microwave-cured materials was also studied by using a scanning electron microscope(SEM) in order to analyze the morphology of cured specimens.

Abstract: The curing rate of epoxy/Versamid 125 (V125) by heating curing, room-temperature curing and microwave curing was compared. It is founded that applying microwave technology could effectively improve the curing rate and the curing time is only 3-4minutes. 140W microwave could cure the epoxy system in good condition, but 280W and 420W were easy to make the materials coking. The impact of diluent on mechnical properties of curing product were studied and it is showed that the impact strength increases and the impact ductility will be improved with the content of diluent increases, while the compressing strength, bending strength and tensile strength decrease.

Abstract: Nano-Fe particles were selected as microwave-absorber, and added in the epoxy resin. Epoxy resin/nano-Fe composite materials were cured by microwave irradiation and heating. Vector network analysis, dynamic mechanical analysis(DMA) and scanning electron microscope(SEM) were used to study the curing behaviors of composite materials under the different curing ways. Results show that the dielectric constant(εr) and the dielectric loss factor(tanδ) of the epoxy resin increased obviously when nano-Fe particles were added, and microwave absorption properties of epoxy resin/nano-Fe composite materials improved greatly with increasing contents of nano-Fe particles. DMA results indicate that the storage modulus (E’) and glass transition temperature(Tg) of epoxy resin samples with nano-Fe particles were higher than those without nano-Fe particles. The microstructure and phase composition of the samples were studied by SEM and EDX. Results show that nano-Fe particles were homogeneously dispersed in the epoxy resin matrix under microwave irradiation, which implies improved strength and toughness of epoxy resin/nano-Fe composite materials.

Abstract: Two biphasic BCP ceramic samples were synthesized by chemical precipitation and microwave curing of calcium deficient hydroxyapatite CDHA under the same pH value and temperature but varied in their initial Ca/P molar ratio. Precipitates were characterization after thermogravimetric analysis, fourier transform infrared spectroscopy, X-ray diffraction, atomic absorption spectroscopy and TEM. Hydroxyapatite (HA) contents were measured for the two biphasic calcium phosphate (BCP) ceramics by sintering the calcium-deficient apatites (CDHA). The results reveal two condensation mechanisms of HPO42- affecting the Ca/P molar ratio after calcination. The X-ray diffraction patterns of BCP powders show the in situ formation of -TCP in the BCP powder. The amount of -TCP phase increases as the initial Ca/P molar ratio decreases due to more calcium deficiency in CDHA structure. The influence of HPO42- incorporation on increasing -TCP phase content after calcination is evaluated. TEM micrographs proved the effect of microwave curing during the preparation process on reducing of particle size to nanoscale range and the destruction of CDHA to finer HA and -TCP particles upon calcination.