Crystallization Kinetics, Morphology, and Mechanical Properties of Novel Biodegradable Poly(ethylene succinate-co-ethylene suberate) Copolyesters

Abstract

Through a two-step melt polycondensation method, three poly­(ethylene succinate-co-ethylene suberate) (PESSub) copolymers containing different contents of ethylene suberate (ESub) from 4.8 to 15.3 mol % and with similar molecular weights were successfully synthesized in this research. To demonstrate the effect of the ESub composition, the crystallization kinetics, morphology, and mechanical properties of PESSub were systematically studied. The crystal structure of PESSub was the same as that of PES; however, with increasing ESub composition, the degree of crystallinity values slightly decreased. The increase of the ESub content led to a depression in the glass transition temperature, cold crystallization temperature, cold crystallization enthalpy, melting point, heat of fusion, and equilibrium melting point of PESSub. Increasing the ESub composition retained the crystallization mechanism but decreased the crystallization rates and spherulitic growth rates. The copolymers with higher ESub component showed greater elongation at break but smaller tensile strength and Young’s modulus. The crystallization behavior and mechanical properties of the synthesized novel copolyesters were well-regulated by adjusting the content of the ESub units.

Disclosing the crystallization behavior and morphology of poly(ϵ‐caprolactone) within poly(ϵ‐caprolactone)/poly(l‐lactide) blends

“…Figure shows typical Avrami plots for pure PCL and PCL/PLLA blends crystallized at 35, 40 and 45 °C, respectively. As illustrated, the Avrami plots of pure PCL and PCL/PLLA blends display almost parallel straight lines, suggesting that the isothermal crystallization kinetics are in good agreement with the Avrami equation . The parameters k and n were separately obtained from the interceptions and slopes of the Avrami plots.…”

“…The values of n varied slightly between 2.3 and 3.0 for both the neat PCL and the PCL/PLLA blends within the investigated T c range, indicating that the crystallization mechanism of PCL homopolymer and PCL/PLLA blends corresponds to three‐dimensional spherulitic growth and heterogeneous nucleation. In addition, the almost unchanged n values also indicate that the blending with PLLA did not affect the crystallization mechanism and the geometry of the crystal growth of PCL …”

“…As illustrated, the Avrami plots of pure PCL and PCL/PLLA blends display almost parallel straight lines, suggesting that the isothermal crystallization kinetics are in good agreement with the Avrami equation. 57 The parameters k and n were separately obtained from the interceptions and slopes of the Avrami plots. For comparison, the Avrami parameters are summarized in Table 1.…”

“…In addition, the almost unchanged n values also indicate that the blending with PLLA did not affect the crystallization mechanism and the geometry of the crystal growth of PCL. 57,58 In addition, the k values of neat PCL and PCL/PLLA blends are also listed in Table 1. However, they were not suitable for direct comparison of the overall crystallization rates of PCL because the unit of k was min −n and the n values were not constant for all samples.…”

“…The crystallization half-time (t 1/2 ) corresponds to the time required to achieve 50% of the final crystallinity of the samples, 57,60 which is often chosen as a key parameter to characterize the overall crystallization kinetics; it could be calculated according to Eqn (2). Table 1 also lists all the t 1/2 values for neat and blended PCL at different T c values.…”