Bio-based Copolyesters from p-Hydroxybenzaldehyde: Synthesis, Characterization and Thermo-Mechanical Properties

Petroleum-based polyesters are widely used in daily life. However, their reliance on petroleum resources and non-biodegradability have raised concerns. Due to the advantages of being renewable, degradable, and abundant, bio-based polyester is expected to become a breakthrough in replacing petroleum-based polyester. In this study, p-hydroxybenzaldehyde, a bio-based monomer, was used to synthesize a novel diol, 2,2′-(4-((4-ethylphenyl)diazenyl)phenylazanediyl)diethanol (EDPD). The EDPD was then polymerized with 1,4-cyclohexanedimethanol (CHDM) and aliphatic diacids to synthesize a series of aliphatic-aromatic polyesters. Thermal analysis showed that the Tg varied from 43°C to 104°C, while the melting point (Tm) varied from 118°C to 156°C. All the polyesters exhibited high yield strengths (48–79 MPa) and tough values (elongation at break of 240–330%). After 30 weeks of soil incubation, the mass loss of the copolyester could reach 4.3%. The investigation of the eco-toxicity of the copolyesters showed that the survival rate of Eisenia foetida was more than 80%, demonstrating their low toxicity in natural habitats. The copolyesters investigated in this study exhibited good thermal, mechanical, and biodegradability properties. The properties of the copolyesters can be adjusted by varying the length of the carbon chains of the dicarboxylic acid moieties. These bio-based copolyesters could provide an important way to promote carbon neutrality and sustainable development of bio-based plastics.