Polypropylene/graphite intercalation compound (PP/GIC) composites are prepared via melt mixing at three different temperatures (180, 200, and 220 °C). The dispersion of GICs in the composites is clearly improved due to the increased interlamellar spacing caused by in situ expansion of GICs at higher temperatures, which facilitates the intercalation of PP molecular chains into the GIC galleries. As a result, the PP/GIC composite with 10 wt% GICs prepared at 220 °C (PG220) presents a dielectric constant of about 1.3 × 108 at 103 Hz, which is about six orders higher than that of the composite prepared at 180 °C (PG180). Moreover, the thermal conductivity of the PG220 sample (0.63 Wm−1K−1) is 61.5% higher than that of the PG180 sample. The well-dispersed GICs accelerates the crystallization of PP by increasing the nucleation point and enhances the thermal stability of the composites. The PG220 sample shows a Young’s modulus that is about 21.2% higher than that of the PG180 samples. The results provide an efficient approach for fabricating polymer/GIC composites without complex exfoliation and dispersion processes.

Optical glass-microprism arrays are generally embossed at high temperatures, so an online cooling process is needed to remove thermal stress, but this make the cycle long and its equipment expensive. Therefore, the hot-embossing of a glass-microprism array at a low strain rate with reasonable embossing parameters was studied, aiming at reducing thermal stress and realizing its rapid microforming without online cooling process. First, the flow-field, strain-rate, and deformation behavior of glass microforming were simulated. Then, the low-cost microforming control device was designed, and the silicon carbide (SiC) die-core microgroove array was microground by the grinding-wheel microtip. Lastly, the effect of the process parameters on forming rate was studied. Results showed that the appropriate embossing parameters led to a low strain rate; then, the trapezoidal glass-microprism array could be formed without an online cooling process. The standard deviation of the theoretical and experimental forming rates was only 7%, and forming rate increased with increasing embossing temperature, embossing force, and holding duration, but cracks and adhesion occurred at a high embossing temperature and embossing force. The highest experimental forming rate reached 66.56% with embossing temperature of 630 °C, embossing force of 0.335 N, and holding duration of 12 min.

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Poly(vinylidene fluoride)/polyamide 6/expanded graphite (PVDF/PA6/EG) composite is prepared via one-step melt extrusion. The EG is well dispersed with the addition of PA6 and mainly distributed in the PA6 phase due to the stronger affinity between them. As a result, the PVDF/PA6/EG sample presents higher dielectric permittivity than the PVDF/EG sample and maintain a low dielectric loss due to its sea-island phase structure, which impedes the formation of conductive path in the composite. The mean interlayer spacing of the EG in the polymer matrix decreases obviously due to its improved dispersion state, which is in favor of the phonon transportation in the composite. As a result, the PVDF/PA6/EG sample exhibits a significantly improved thermal conductivity of about 0.48 W m À1 K À1 , which is 140% higher than that of the PVDF sample and 37% higher than that of the PVDF/EG sample. Moreover, the PVDF/PA6/EG sample presents higher Young's modulus and tensile strength than the PVDF/EG sample. While the elongation at break of the PVDF/PA6/EG sample is only a little lower than that of the PVDF/EG sample. This means that the tensile properties of the composite are not destroyed obviously by melt blending with the immiscible PA6.