Effects of the shapes and addition amounts of crosslinking reagents on the properties of poly-3-hydroxybutyrate/poly(caprolactone) blends

The effects of the shapes and addition amount of crosslinking reagents on the expression mechanisms of polymer properties of poly(3-hydroxybutyrate) (PHB) and poly(caprolactone) (PCL) blends are investigated. A static tensile test is carried out on 60%PHB/40%PCL blends by adding liquid and solid crosslinking reagents, showing that the Young's modulus of the blends decrease with increasing effective peroxide value of the crosslinking reagent. In addition, the elasticity of the blends increases only when the liquid crosslinker is added, even though T1H analysis and scanning electron microscopy observation reveal that both crosslinking reagents improve the miscibility of the blend. Furthermore, the H-1 and C-13 PST-MAS NMR spectra related to the molecular motions of polymer main chains in the blends increase with increasing effective peroxide value of the crosslinking reagents. However, the local molecular motions of substituents in the blends matched with the T1C values reveal an opposite trend between the rigid PHB and flexible PCL with the addition of the solid crosslinker. The solid-state NMR spectral and relaxation time analyses suggest the possibility of the polymer chain scission as a side reaction, as well as the occurrence of intra-domain crosslinking, both of which reduce the toughness of the blends containing the solid crosslinker.

Automated summary

The study investigated the effects of various shapes and addition amounts of crosslinking reagents on the expression mechanisms of polymer properties in PHB and PCL blends. It was found that the elasticity of the blends increased with the addition of liquid crosslinking reagents, while the toughness decreased with the addition of solid crosslinking reagents.