This paper is concerned with the nature and morphology of deposited Carbon -Alumina coatings produced under various discharging conditions of the Impulse Plasma Deposition (IPD) process. The deposition of the coating material was carried out on a non-heated steel substrate by means of plasma pulses generated from a coaxial plasma gun. The pulsed plasma mainly consists of two kinds of ions: working gas ions and inner electrode ions. Coatings were produced by a number of plasma pulses (50 -200) from 15.42 µF capacitor bank at 13.5 kV discharging voltage. The microstructure of the deposited films was observed using scanning electron microscope (SEM). Structural features were greatly affected by the type of the working gas which controls the ionization potential. Using the Acetylene (C 2 H 2 ) only as a working gas produces a layer of graphite and coarse alumina particles (AL 2 O 3 ) with non uniform distribution. Mixing the used gas with a molecular gas (either N 2 or H 2 ) enhances the ionization and gives more uniform distribution of finer alumina particles.
Epoxy resins are widely utilized as high performance thermosetting adhesives. Polyamide cured epoxies provide improved flexibility, moisture resistance, and adhesion. Moreover, Versamid could provide lower viscosity, better compatibility, and better cure profiles under adverse conditions. Thus, the use of polyamide (Versamid 125) as a curing agent and HTPB as an elastomeric rubbery modifier give this study an importance in formulating adhesives to be used in high temperature applications. A systematic study has been conducted to investigate the modification of DGEBA-based epoxy systems by the incorporation of hydroxyl-terminated polybutadiene (HTPB) as an elastomeric rubbery modifier in different proportions (0.75, 1.5, 2.5, 5, and 10% by weight) into an epoxy resin. Mechanical mixing process, accompanied with vacuum to get rid of cavitations, was employed to disperse the particles homogeneously into the resin system. Thermal and mechanical properties of the composite and the neat resin were measured with DSC, Zwick universal test machine, and Zwick durometer hardness tester. The composite shows an improvement in stress, strain, shore D hardness, flexural and compressive values. Nearly 2.5% of HTPB was quite enough to obtain a compromise of the desired mechanical and thermal properties. The detected decrease in T g as the rubber content increases means that this modifier can enhance plasticity of the matrix. Reduction in the cross-linking density of the thermoset because of the added modifier has been confirmed and explained.
KeywordsEpoxy resins/ Adhesives/ Modifiers/ Thermal and mechanical properties / HTPB. Egyptian Armed Forces
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