서강대학교

초록/요약

Conventional highly filled polymer composites have been produced based on monomeric binders because of low impregnation and pore generation during processing. The monomeric binder polymer composites should involve a (curing) reaction process in addition to the particle dispersion processing. In order to improve the inefficient production process of such a monomer binder, researches on the production process of highly filled composite materials based on thermoplastic resin have recently been conducted. Unlike monomeric binders, thermoplastic binders have high viscosity, which makes it difficult to develop the manufacturing process. In this study, we have developed better and more economical process which can produce highly filled thermoplastic composites in one step continuous twin extrusion process. In the previous PBX manufacturing field, HTPB and IPDI have been used as binder for a large amount of explosives. The effect of temperature rising rate and catalyst type on the reaction of HTPB and IPDI binder was confirmed. The energy of each curing reaction was calculated by DSC and the activation energy was also determined by applying it to some plot. The reaction rate constant and pre-exponential factors were also evaluated to predict the curing completion time according to the curing temperature. From those results, it was found that a curing process, depending on temperature, of 4 days or more was required in addition to the particle dispersion process. From the rheological point of view, the cure behavior was also confirmed. The binder structure was constant at the gel point regardless of temperature, and the activation energy was also consistent with DSC results. The characteristics of highly filled thermoplastic composites were analyzed in order to overcome the disadvantage of monomer binder. In unimodal particle system, the viscosity increased with exponentially according to the content of fillers and the viscosity measured by rotational rheometer in different stress control was changed. It is confirmed that the Cox-Merz rule cannot be applied anymore in this system. In the case of two particles having different sizes, the viscosity tendency was different according to the size ratio between particles and small particle fraction. The reason for the minimum viscosity behavior at a ratio greater than the theoretical size ratio is due to the size distribution of the particles. For the maximum packing fraction of particles, it is important to improve the dispersibility of the polymer composites material. The effect of particle feed sequence, the use of plasticizer to reduce binder viscosity, the influence of screw type, and finally, the application of supercritical fluid to the twin screw extrusion process improved the dispersibility of the polymer composites. In the case of highly filled thermoplastic composites, high viscosity can cause many processing problem. A study was carried out to stabilize the twin screw extrusion process using various extrusion process conditions. A suitable diameter size of die for highly filled composites was determined. Through a vacuum degassing or vent step, residual air injected with the particles was removed and the effect of OD/ID ratio change on extruder was confirmed. More stable process was organized when the OD/ID ratio was 1.88 and appropriate L/D was also found. In addition to production process, quantitative analysis of composites content was also studied. In the case of TGA, there was a large error in the content analysis when the final residue was present. The ATR with relatively accurate results and safety decreased in accuracy as the number of particles increased. NMR analysis was able to determine exact content, but it was difficult to find a appropriate solvent. Density analysis through comparison with theoretical evaluation results can be measured immediately after processing, and defects due to residual air can be confirmed. Furthermore, the effect of the characteristics of the particles was also verified by comparing the rheological properties of the PBX and its simulant. The results of this study can be utilized as information for practical application of PBX manufacturing process.