Miscibility and crystallization behaviors of poly(3‐hydroxybutyrate‐co‐11%‐4‐hydroxybutyrate)/Poly(3‐hydroxybutyrate‐co‐33%‐4‐hydroxybutyrate) blends

Abstract

Biopolyesters poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with an 11 mol % 4HB content [P(3HB-co-11%-4HB)] and a 33 mol % 4HB content [P(3HB-co-33%-4HB)] were blended by a solvent-casting method. The thermal properties were investigated with differential scanning calorimetry. The single glass-transition temperature of the blends revealed that the two components were miscible when the content of P(3HB-co-33%-4HB) was less than 30% or more than 70 wt %. The blends, however, were immiscible when the P(3HB-co-33%-4HB) content was between 30 and 70%. The miscibility of the blends was also confirmed by scanning electron microscopy morphology observation. In the crystallite structure study, X-ray diffraction patterns demonstrated that the crystallites of the blends were mainly from poly(3-hydroxybutyrate) units. With the addition of P(3HB-co-33%-4HB), larger crystallites with lower crystallization degrees were induced. Isothermal crystallization was used to analyze the melting crystallization kinetics. The Avrami exponent was kept around 2; this indicated that the crystallization mode was not affected by the blending. The equilibrium melting temperature decreased from 144 to 140 C for the 80/20 and 70/30 blends P(3HB-co-11%-4HB)/ P(3HB-co-33%-4HB). This hinted that the crystallization tendency decreased with a higher P(3HB-co-33%-4HB) content.

Isothermal Crystallization Kinetics, Morphology, and Mechanical Properties of Biocomposites Based on Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and Recycled Carbon Fiber

“…A single T g was also detected at around −3 °C from the DSC traces. It is interesting to note that both neat P(3,4HB) and its composite exhibit a unique dual cold crystallization behavior, in which two T p s are denoted as T p1 and T p2 from low to high temperatures at the given heating rates . According to the investigation on the crystalline structure of P(3,4HB) by WAXS in the following section, there was no transformation of crystal form observed when the annealing temperature was changed.…”

“…It is interesting to note that both neat P(3,4HB) and its composite exhibit a unique dual cold crystallization behavior, in which two T p s are denoted as T p1 and T p2 from low to high temperatures at the given heating rates. 32 According to the investigation on the crystalline structure of P(3,4HB) by WAXS in the following section, there was no transformation of crystal form observed when the annealing temperature was changed. Therefore, this phenomenon of multiple cold crystallizations is due to the improvement of crystalline integrity, i.e., the perfection of an integrated crystal like spherulite, resulting from the annealing process.…”