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The effect of tetragonal‐zirconia nanoparticle inclusion on the temperature‐dependent storage modulus, or the temperature‐degradation rate, of polyethylene glycol (PEG)‐based composites was investigated using shear‐mode dynamic mechanical analysis (DMA) at temperatures ranging from room temperature up to 75°C. We carried out further investigations in the rubbery area in terms of the characteristic of the degradation rate with temperature and compared it with silica‐quartz‐filled PEG composites, which exhibited a potential as phase‐change materials (PCMs). The investigation began by plotting the shear storage modulus (G′) of the composites and observing the slopes of the curves in the range of the rubbery area, which were assumed to follow a straight‐line equation. Then, we completed the investigation by developing and introducing a temperature‐dependent storage modulus model in the rubbery area for describing the storage modulus of such filler‐dispersed PEG/inorganic composites, to yield the degradation rates of the composites. The new model includes parameters k1 and C that are associated with the degradation rate and the amount of a filler, respectively. The model shows a satisfactory agreement with the experimental data of G′ in the rubbery area, being parameter k1 is associated with a linear degradation rate.

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Abstract. Zircon powders have been produced from raw materials of amorphous zirconia and amorphous silica powders obtained from natural zircon sand of Kalimantan Tengah, Indonesia. Synthesis process was started with the extraction of zircon powder to produce sodium silicate solution and pure zircon powder. The amorphous zirconia and silica powders were prepared by alkali fusion and co-precipitation techniques. The powders were mixed using a planetary ball mill, followed by a calcination of various holding time of 3, 10, and 15 h. Phase characterization was done using X-Ray Diffraction (XRD) technique and analysis of the diffraction data was carried out using Rietica and MAUD software. The identified phases after the calcination were zircon, tetragonal zirconia, and cristobalite. The highest zircon content was obtained in the sample calcinated for15 hours -reaching 99.66 %wt. Crystallite size analysis revealed that the samples calcinated for 3, 10, and 15 h exhibited zircon crystal size of 176 (1) nm, 191 (1) nm and 233 (1) nm respectively.

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