Green recycling of aluminum plastic packaging waste by solid-state shear milling and 3D printing for thermal conductive composites

Aluminum-plastic packaging is a multilayer material composed of polymer and aluminum, which has been applied in food, medical, and other fields, due to the excellent fresh-keeping and barrier performance. However, it is difficult to recycle aluminum-plastic packaging waste (APPW) due to the complicated components and the low value of reclaim products. This paper reports a green way to recycle the APPW by solid-state shear milling ((SM)-M-3) technology and then fabricate APPW/expandable graphite (EG) composite parts with high thermal conductivity by fused deposition modeling (FDM) process. After the (SM)-M-3 treatment, the ultrafine APPW powder with the size of 7 similar to 8 um was obtained, and it showed excellent processibility and the APPW/EG composite parts were successfully processed by FDM technology. The APPW/EG three-dimensional (3D) printed parts showed excellent mechanical and heat transfer performance along the stretch direction (0 degrees), where the tensile strength and thermal conductivity reached 13.58 MPa and 2.71 W/mK for APPW/EG (80/20) composites, respectively, much higher than those of pure APPW composite (7.71 MPa and 0.62 W/mK). Theoretical calculations showed that the interfacial thermal resistances of APPW/EG 3D printed parts with aligned fillers were lower than other samples. Furthermore, the APPW/EG composites with 20 wt.% EG loading showed a low electrical conductivity of 10(-10) S/cm because the oxidation layer was formed on the surface of Al flakes during the (SM)-M-3 process, which can be used in the thermally conductive insulating field. The new strategy presented in this work provides a new sight to recycle APPW for value-add material.

Automated summary

Aluminum-plastic packaging waste is difficult to recycle due to its complex composition and low value of reclaim products. However, a green recycling method using solid-state shear milling (SM)-M-3 technology has been reported in this study, allowing the fabrication of high thermal conductivity APPW/expandable graphite (EG) composite parts.