Thermal interface materials (TIMs) are one of the important components of materials used in electronic packaging processes to reinforce the interface heat transfer between electronic components. High thermal conductive filler-reinforced polymer composites are receiving increasing attention in electronic packaging for their excellent thermal conductivity and low cost, but their applications are limited by complex preparation processes and difficult to produce on large scale. This paper presents an efficient blending method with dry ice airburst synergistic shear force field for large-scale preparation of natural rubber/expanded graphite (NR/EG) polymer composites. The thermal conductivity of the composite in presence of dry ice airburst is 2.317 W/(m·K) for EG content of 30 wt%, compared to 1.206 W/(m·K) for the control sample without dry ice airburst, an improvement of 92.1%, indicating a significant improvement in thermal conductivity. In addition, after introduction of dry ice, tensile strength and elongation at break of composites increased by 33.7% and 9.2%, respectively, showing promising mechanical properties. The calculations showed that the shear flow field strength was increased 68.2 times by heat absorption of dry ice, and the EG exfoliation mechanism was proposed. The strategy proposed in this work provide green, simple and efficient method to prepare high thermal conductive composites without the involvement of chemical solvents, which has enormous potential in large-scale preparation of high thermal conductivity filler reinforced polymer composites.
Jingyu Chen,Dingyi Duan,Sen Xue,Yongzheng Zhang,Kai Wu,Qiang Fu
Owing to the limited solubility of cellulose in conventional solvents, the development of efficient solvent systems to dissolve cellulose is necessary for its subsequent processing into value-added cellulose-based materials. In recent years, a green, low-cost, and sustainable CO2-based reversible solvent system (CO2/DMSO/DBU) has been developed. In this system, dimethyl sulfoxide (DMSO) facilitates the swelling of cellulose, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) provides a strong alkaline environment, enabling the derivatization of cellulose with CO2 to form cellulose carbonate, which is soluble in the solvent. Nevertheless, these systems have drawbacks, including high temperature (>50 °C) and inadequate mechanical properties of the regenerated cellulose films. In this study, ball milling was used to lower the dissolution temperature of cellulose and further improve the mechanical properties of regenerated cellulose films. To do this, dry ice as a source of CO2 and DMSO/DBU as mixed solvents, together with cellulose, were ball-milled at room temperature. A series of regenerated cellulose films were prepared at different dry ice contents and ball milling times. The results demonstrate that the cellulose can be readily dissolved within 0.5 h at room temperature, resulting in a stable cellulose solution (4.48 wt%), thanks to the mechanochemistry provided by ball milling. The prepared regenerated cellulose films exhibit satisfactory mechanical properties with a tensile strength of up to 77.3 MPa and a tensile strain of 8.6%, which are among the highest values reported for regenerated cellulose films. This work illustrates a simple, mild, and efficient method for green cellulose processing.
危险品化学品经营许可证（带存储）