Experimental Investigation on Ablation Characteristic of EPDM Insulator in Different Gas Environments

Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.

Experimental Research on Dynamic Erosion of EPDM Insulation Subjected to Particle-Laden Flow

The instantaneous degradation of erosion surface of ethylene propylene diene monomer(EPDM)insulation subjected to the particle-laden flow in two operating conditions was measured by using a real-time X-ray radiography system.The images of its erosion state and dynamic ablation rate were obtained.And the charring-layer was analyzed by using SEM and energy spectrum.The experimental results indicate that the erosion rate of EPDM insulation layer impacted by low speed and low concentration particle flow is relatively small in the 1st second since the motor starting,but increases rapidly in 1 to 2.5 s,while the erosion rate of EPDM insulation layer impacted by high speed and high concentration particle flow increases rapidly in the 1st second;the ablation rate at the section eroded intensively by particle flow increases at first,then decreases,and goes to stabilization after 4.5 s;the higher speed and concentration particle flow are,the deeper particles get into charring layer,which lead to more thermal increment and thinner charring layer.

Flame retardant synergy between interfacial and bulk carbonation in glass fiber reinforced polypropylene

Glass fiber reinforced polypropylene(GF-PP)composites have high flammability on account of wick effect which leads to accelerated flow of the polymer melt along the glass fibers(GF)surface to the flame zone.In this study,dipentaerythritol(DPER),a charring agent,was adsorbed on the GF surface through the hydrogen bond between silane coupling agent and DPER.DPER has a synergistic effect with the intumescent flame retardants(IFR)added in the composites,which can induce interfacial carbonization on the surface of GF,thus transforming the intrinsic smooth GF surface into roughness one.In this way,the negative effect of the wick effect in flame retardancy is weakened.Moreover,the char residues remained on the surface of GF can bring an improved adhesion between GF and char residues formed in the resin so that a more stable barrier char layer is formed.The PP composites with 20 wt%modified glass fiber(M-GF)and 30 wt%IFR can achieve the UL-94 V-0,and its limiting oxygen index(LOI)value increased from 16.5%to 29.5%.Simultaneously,the heat release rate(HRR),total heat release(THR)and total smoke release(TSR)decreased significantly,and the peak of heat release rate(PHRR)reduced60.6%compared with GF-PP.

Ablation characteristics of insulator under high-temperature gas dual-pulse erosion

This study numerically simulated and investigated the flow field characteristics of a typical dual-pulse solid rocket motor with a soft pulse separation device through thermal insulation ablation under high-temperature dual-pulse erosion.The ablation rate of ethylene-propylene-diene monomer(EPDM)insulator was measured after the experiment.Experimental results were analyzed through scanning electron microscopy and microcomputed tomography.The ablation mechanism of the EPDM insulator under the operation conditions of a dual-pulse solid rocket motor was evaluated by analyzing the results.The results reveal that the internal flow field of the motor with a soft pulse separation device is uniform.The original charred layer existing on the EPDM insulator surface in the first pulse combustor is the decisive factor affecting the final ablation rate of the dual-pulse motor during the second pulse operation,and the ablation characteristic region is easily formed with the exfoliation of the charred layer.The ablation rate difference of the insulator increases with gas velocity.