In developing flow behavior of plasticized prepolymer as liquid content of composite solid propellant, zero shear viscosity (ZSV) is a critical parameter that Goh-Wan equation is developed to model it recently [1]. Thus, this work aims to analyze the compatibility of the Goh-Wan equation toward the liquid content of propellant, characterize it, and determine the limit. In this work, a varied flow behavior index was obtained by using Hydroxy terminated polybutadiene (HTPB) and HTPB-DOA (Dioctyl adipate) system with the variable of its concentration, pre-heating, and pre-stirring methods as samples. Viscosity was measured at 2, 3, 4, and 5 rpm by using the disc spindle of Brookfield viscometer. For the minimum shear-rate investigation, as a limit of compatibility, other three sets of shear rates are applied, which are 0.6 – 5 rpm, 1 – 5 rpm, and 1,5 – 5 rpm. By functioning Goh-Wan equation (model 1) and Power-Law (model 2), a model was categorized as compatible if yields lower value of ZSV than the first experimental measured viscosity (η1st). Characterization was determined by a graph of plotting percentage difference of ZSV obtained from models 1 and 2 towards the index of flow behavior. The 3% of the difference between ZSV obtained from model 1 and η1st was set to be a minimum value for a set of applied shear-rate to be acceptable. It is reported that the Goh-Wan model is compatible with the liquid content of propellant and characterized by a perfect linear correlation. It is also found that a minimum applied shear rate of 1.5 rpm is acceptable for model compatibility.
Analisis rheologi perlu dilakukan terhadap slurry propelan untuk mengetahui viskositas dan castability-nya. Hal ini berpengaruh pada tingkat homogenitas dan nilai Isp sebagai karakteristik utama propelan padat komposit. Penelitian ini bertujuan untuk mengetahui karakteristik rheologi slurry propelan berbasis HTPB dan DOA menggunakan analisis viskositas. Metode pengukuran viskositas dilakukan dengan parameter suhu, waktu curing dan shear rate. Hasil pengukuran menunjukkan bahwa viskositas menurun dengan kenaikan suhu dan juga sebaliknya, viskositas meningkat dengan bertambahnya waktu curing. Melalui persamaan Power Law, diperoleh Koefisien konsistensi (K) antara 2,1148-2,2877 yang nilainya meningkat seiring dengan turunnya temperatur. Bertambahnya nilai K mengartikan energi yang dibutuhkan oleh unit operasi untuk mencetak propelan ke dalam tabung cetakan juga semakin meningkat. Sedangkan nilai indeks sifat alir (n) antara 0,1535-0,5128 menunjukkan bahwa slurry propelan merupakan fluida Non-Newtonian dengan perilaku shearthinning (pseudoplastik) karena n<1.
HTPB is the ultimate component of matrix builder for high-filled composite materials. Flow behavior of HTPB in low shear is crucial in casting the composite. Considering the characteristics of hydrocarbon, this work aims to investigate the effect of microstructure composition of HTPB on its flow behavior. In this work, HTPB with different composition of 1,4-cis, 1,2-vinyl and 1,4-trans microstructures were used. Fourier-Transform Infra-Red spectroscopy (FT-IR) was used to determine the composition. It was calculated as a ratio of peak area of 710, 910 and 970 cm-1 for 1,4-cis, 1,2-vinyl, 1,4-trans isomers respectively. Viscosity was measured using a rotational viscometer at various low shear rates. It is found that HTPB with high 1,2-vinyl/1,4-trans isomers shows shear thickening behaviour, distinguished significantly from Newtonian flow of the others. It is suggested that mechanism of shear thickening involves a certain configuration of 1,2-vinyl and 1,4-trans isomers that builds different degrees of flow resistance from one to other shear layers. The configuration and flow resistance changes among layers as shear increases.
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