Research On The Forming Method Of PP/CF Die-drawn Prefabricated Blanks Based On Sand Canal-stone Canal Transformation

With the rapid development of aerospace technology,micro-manufacturing technology and assembly technology,and 5G communication technology,the degree of integration and powerization of products,equipment,and various components is increasing,resulting in an increasingly prominent problem of rapid heat accumulation.However,there is a big bottleneck in exploring methods to enhance the thermal conductivity of polymer composites and improve the thermal conductivity/heat dissipation capacity of polymer composites.Although the thermal conductivity can be improved by an order of magnitude in theory,the actual improvement effect is often not ideal.It is necessary to introduce new ideas and new performance enhancement methods to achieve greater breakthroughs.Even though many domestic articles have reported many methods for preparing high thermal conductivity composite,they are often limited by processing efficiency,cost,etc.in practical applications,and it is difficult to achieve industrialized and continuous production.This paper mainly proposes and verifies a transformation theory based on"sand canal-stone canal",and combines the space confined forced assembly method（SCFNA）based on the theory with injection molding,and proposes a multiple injection-compression molding method.Multiple injection-compression molding processing method is expected to achieve industrial application.The main contents are as follows:（1）The transition mechanism of“sand canal to stone canal”is proposed.On the basis of the SCFNA method,adding different kinds of rigid particles into the polydimethylsiloxane（PDMS）composite significantly improves the thermal conductivity of the composite,proving the feasibility of the theory;among them,the highest thermal conductivity can be up to 23.415 W/m·K.（2）An efficient processing method of multiple injection-compression molding is proposed.The PP/CF composites with the same thickness were prepared by injection molding,injection compression molding,and multiple injection-compression molding respectively.The results show that the thermal conductivity of the composite prepared by the multiple injection-compression molding process is 1.26 times that of the injection molding product,and the value is 0.364 W/m·K,which verifies the feasibility and effectiveness of the method.（3）Explore the application of the SCFNA method based on the"sand canal-stone canal"transformation on the injection molding machine and the advantages of the multiple injection-compression molding process.3 mm injection molding,3 mm injection compression molding,3×1 mm and 6×0.5mm PP/CF/SiO₂,PP/CF/Al₂O₃,PP/CF/graphene nanosheets（Gnp）composite were prepared separately,once again verify the feasibility and effectiveness of the multiple injection-compression method;at the same time,the thermal conductivity of PP/CF/Gnp composite is higher than PP/CF/SiO₂,PP/CF/Al₂O₃.（4）Improve the distribution and dispersion effect of graphene,and explore the effect of different PP morphology and graphene micro-platelet（Gmp）content on the properties of composites.The results show that the thermal conductivity of PP pellets/（10 wt%）Gmp composite is 0.374 W/m·K,which is better than that of PP powder/（10 wt%）Gmp.The eccentric rotor extruder blends PP/CF/Gmp to improve the dispersion effect of Gmp.In the preparation of PP/CF/Gmp composite by multiple injection-compression,the thermal conductivity（0.620 W/m K）,elongation at break（6.32%）and tensile strength（15.29 MPa）are much higher than those of PP/CF/Gnp composites blended by screw extruder.