Effect of chain extension on processability and mechanical properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Poly(3-hydroxybutyrate-4-hydroxybutyrate) (P34HB) copolyester is a new type of biodegradable polymer material, but it cannot meet the market requirements because of its poor thermal stability. In this work, P34HB with a low degree of cross-linking was successfully prepared by incorporating a small amount of a multiple epoxy chain extender, known as Joncryl ADR-4380 (styrene-methacrylic acid glycidyl ester copolymer), through reactive extrusion. The rheological properties, thermal stability, thermal behavior, and mechanical properties of the materials were investigated. Fourier transform infrared spectroscopy and gel content test showed that there was a significant chemical interaction between P34HB and ADR4380, and a cross-linked structure was produced. Compared with pure P34HB, the samples after chain extension showed improved rheological properties, with increased viscosity and melt elasticity due to the formation of a gel network. Thermogravimetric analysis, dynamic time scanning experiment, and melt flow index (MFI) provided strong evidence for the enhanced of thermal stability of P34HB. The onset decomposition temperature of P34HB increased by 13.5 degrees C, and its MFI decreased from 23.30 to around 5 at 170 degrees C, and the complex viscosity remained relatively stable with time after modification. In terms of mechanical properties, the maximum elongation at break increased by 88.08% due to the improvement of toughness. Researchers successfully modified and prepared biodegradable material P34HB by incorporating a small amount of Joncryl ADR-4380 through reactive extrusion. The reaction between P34HB and ADR resulted in extended molecular chains and the formation of a low-crosslinked structure, leading to improved rheological properties, enhanced thermal stability, and increased toughness. image