Green preparation of poly (butylene succinate-co-butylene terephthalate) foam with tunable degradability and mechanical properties by supercritical CO2

Poly (butylene succinate-butylene terephthalate) (PBST) with different chain segments was synthesized by in -situ polycondensation, and foams were prepared by supercritical CO2 foaming. The crystallinity and tensile modulus of PBST increases with the aromatic content, slowing down the diffusion of CO2 and enhancing the dimensional stability of PBST foam. The rheological analysis reveals that a higher temperature of PBST modulus platform is correlated with a higher aromatic content, which is more conducive to the cell stability. The foaming temperature window is 60 - 80 degrees C at 30% aromatic content, which moves to 160 - 175 degrees C at 70% aromatic content, and the maximum expansion ratio of PBST foam decreases from 40.7 to 9.8. With the increase of aromatic content from 30% to 70%, there is an obvious improvement in the compressive modulus of PBST foam, from 0.92 MPa to 6.65 MPa, accompanied by a reduction in the weight loss rate of degradation decreased from 10.78% to 3.04% in 10 days. Hence, there is a careful balance between degradability and foamability of PBST foams. Introducing a suitable aromatic content obtained higher strength to improve the cell stability on the premise that the strong degradability can be maintained, which provides an effective strategy to prepare PBST foams with good degradability and favorable mechanical properties.