Non-Isothermal Crystallization Kinetics of Poly(4-Hydroxybutyrate) Biopolymer

Abstract

The non-isothermal crystallization of the biodegradable poly(4-hydroxybutyrate) (P4HB) has been studied by means of differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). In the first case, Avrami, Ozawa, Mo, Cazé, and Friedman methodologies were applied. The isoconversional approach developed by Vyazovkin allowed also the determination of a secondary nucleation parameter of 2.10 × 105 K2 and estimating a temperature close to 10 °C for the maximum crystal growth rate. Similar values (i.e., 2.22 × 105 K2 and 9 °C) were evaluated from non-isothermal Avrami parameters. All experimental data corresponded to a limited region where the polymer crystallized according to a single regime. Negative and ringed spherulites were always obtained from the non-isothermal crystallization of P4HB from the melt. The texture of spherulites was dependent on the crystallization temperature, and specifically, the interring spacing decreased with the decrease of the crystallization temperature (Tc). Synchrotron data indicated that the thickness of the constitutive lamellae varied with the cooling rate, being deduced as a lamellar insertion mechanism that became more relevant when the cooling rate increased. POM non-isothermal measurements were also consistent with a single crystallization regime and provided direct measurements of the crystallization growth rate (G). Analysis of the POM data gave a secondary nucleation constant and a bell-shaped G-Tc dependence that was in relative agreement with DSC analysis. All non-isothermal data were finally compared with information derived from previous isothermal analyses.

Crystallization kinetics of compatibilized blends of polypropylene and polyethylenimine

“…It can be seen in Table 4 that the values of α are nearly constant and are approximately equal to 1 (ranging between 1.1-1.5). Nevertheless, for both the samples, there was a slight increase observed in α values with increase in the crystallinity which means that the difference between Avrami and Ozawa exponent increases with increase in the relative crystallinity [42,48,49]. Therefore, from the above results, we can infer that Mo model is an appropriate approach for explaining the nonisothermal crystallization kinetics and it also supports the conclusions drawn from respective isothermal crystallization behaviour.…”

Effect of 1,2,4,5-Benzenetetracarboxylic Acid on Unsaturated Poly(butylene adipate-co-butylene itaconate) Copolyesters: Synthesis, Non-Isothermal Crystallization Kinetics, Thermal and Mechanical Properties

“…Figure S2 displayed the plot of relative crystallinity as a function of time at different cooling rates. All the experimental results were plotted with the log{−ln[1 − X t (%) ]} as a function of log(t) at the X t (%) ranged from 20-80% and were well fitted by Avrami equation at various [51][52][53]. (See Figure S3) All the Avrami parameters, n and K were linearly regressed to obtain from the slopes and intercepts of the curves for PBABI copolyesters at different cooling rates.…”

Microstructural Changes during Degradation of Biobased Poly(4-hydroxybutyrate) Sutures

“…This treatment has repercussions on the melting behaviour due to the reorganization of constitutive crystals. Thus, the melting temperature becomes close to 72 °C after annealing, a value that contrasts with the temperature of 58 °C determined for melt crystallized samples [ 20 , 21 ]. Stretching of P4HB leads to a significant increase of its rigidity while flexibility is maintained.…”