Cell structure is a key factor that determines the final properties of microcellular polylactide (PLA) product. In the mold opening process, adjusting the rate of mold opening can effectively control cell structure. PLA and PLA composites with a void fraction as high as 50% were fabricated using the mold opening technique. The effects of mold opening rate and the addition of nanoclay on the cell structure, mechanical properties, and surface quality of microcellular PLA and PLA composites samples were investigated. The results showed that finer cell structure was received in the microcellular PLA samples and the surface quality was improved effectively when decreasing the rate of mold opening. The effect of mold opening rate on the foaming behavior of microcellular PLA–nanoclay was the same as that of microcellular PLA. The addition of 5 wt % nanoclay significantly improved the foaming properties, such as cell density, cell size, and structural uniformity, which consequently enhanced the mechanical properties of foams and the surface quality.

Rapid heat dissipation in dense-power and miniaturised electronic devices is becoming increasingly crucial as electrical technologies improve. Scientists have developed a number of thermal-conductive materials to enhance heat dissipation. Since then, polymer composites have attracted a lot of attention for their lightweight, anti-corrosion, and electrical insulating properties. Interfacial thermal resistance (ITR) is one of the most critical factors to elevate the thermal conductivity of composites. Toward ITR, the molecular dynamic (MD) simulation demonstrates its powerful capabilities for interpreting and predicting macroscopic thermal phenomena based on calculated microscopic structures, thermodynamics, kinetics, and other information. To make full use of MD simulations, one needs to validate the simulation results to ensure that the MD simulation is correctly carried out and the findings are meaningful, reliable and of good repeatability. With these considerations in mind, we highlight the role of MD simulations in heat transfer, the technical issues associated with the nonequilibrium molecular dynamic (NEMD) simulation, the analysis methods for the underlying mechanism, and the strategies to reduce ITR. Furthermore, we also make comments on the perspective of MD simulations in heat transfer.

Understanding heat transfer across an interface is essential to a variety of applications, including thermal energy storage systems. Recent studies have shown that introducing a self-assembled monolayer (SAM) can decrease thermal resistance between solid and fluid. However, the effects of the molecular structure of SAM on interfacial thermal resistance (ITR) are still unclear. Using the gold–SAM/PEG system as a model, we performed nonequilibrium molecular dynamics simulations to calculate the ITR between the PEG and gold. We found that increasing the SAM angle value from 100° to 150° could decrease ITR from 140.85 × 10⁻⁹ to 113.79 × 10⁻⁹ m² K/W owing to penetration of PEG into SAM chains, which promoted thermal transport across the interface. Moreover, a strong dependence of ITR on bond strength was also observed. When the SAM bond strength increased from 2 to 640 $\mathrm{kcal}\mathrm{\cdot }{\mathrm{mol}}^{\mathrm{-}\mathrm{1}}{\mathsf{\AA }}^{\mathrm{-}\mathrm{2}}$, ITR first decreased from 106.88 × 10⁻⁹ to 102.69 × 10⁻⁹ m² K/W and then increased to 123.02 × 10⁻⁹ m² K/W until reaching a steady state. The minimum ITR was obtained when the bond strength of SAM was close to that of PEG melt. The matching vibrational spectra facilitated the thermal transport between SAM chains and PEG. This work provides helpful information regarding the optimized design of SAM to enhance interfacial thermal transport.