Heat insulating PLA/HNTs foams with enhanced compression performance fabricated by supercritical carbon dioxide

Biodegradable PLA foams are in great demand in many fields such as packaging and construction. However, foaming ability of PLA is confined by its poor melt viscoelasticity. To address this problem, a naturally formed nanofiller, halloysite nanotubes (HNTs) were added. By adding HNTs, foaming window of PLA was successfully extended. The compressive performance and thermal conductivities of the obtained foams were investigated. It could be seen that the PLA/HNTs composite foam with an expansion ratio of 19.2 folds exhibited the lowest thermal conductivity 34.29 mW/(m center dot K). The compressive modulus increased from 3.6 to 11.8 MPa with the increase of mass fraction of HNTs from 0 to 5 wt%. To further improve the compressive performance of foams, an annealing process was conducted. After annealing, compressive modulus of pure PLA foam almost doubled because of the increased crystallinity. Vicat softening temperature of annealed foams also increased by about 5 degrees C.

Automated summary

The addition of halloysite nanotubes (HNTs) to PLA improved its foaming ability, and an annealing process further increased the compressive performance of the foam.