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. 2022 Jan 22;14(3):442.
doi: 10.3390/polym14030442.

The Isothermal and Nonisothermal Crystallization Kinetics and Morphology of Solvent-Precipitated Nylon 66

Chiah-Hsiung Tseng  1 , Ping-Szu Tsai  1
Affiliations

The Isothermal and Nonisothermal Crystallization Kinetics and Morphology of Solvent-Precipitated Nylon 66

Chiah-Hsiung Tseng et al. Polymers (Basel). .

Abstract

Solvent-precipitated nylon 66 (SP PA66) is a key material used to fabricate microfiltration membranes. The crystallization kinetics and behavior of SP PA66 were investigated through differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD). The Avrami equation was used to describe the isothermal crystallization of SP PA66. Nonisothermal crystallization behaviors were analyzed using Avrami equations modified by Jeziorny, Ozawa and Mo. The Avrami analysis demonstrated that the k values of SP PA66 were higher than those of neat PA66. The  n was between 2 and 3 indicating the presence of two- and three-dimensional mode with thermal nucleation. With an increasing cooling rate, the Jeziorny crystallization rate constant increased for SP PA66; however, the Ozawa model was not satisfactory for all SP PA66 samples. The Mo method suggested that SP PA66 had a faster crystallization rate than neat PA66 during the nonisothermal crystallization process. The solvents dissolved nylon 66, rearranged it and formed a regular hydrogen-bonded region. These regions served as nucleation sites and increased the crystallization rate constant in the subsequent melting process. The crystal morphology of the SP PA66 under the POM investigation exhibited Maltese cross spherulites. The sizes of the spherulites of SP PA66 were significantly smaller than those of neat PA66. Wide-angle XRD revealed that SP PA66 had the same crystal structure and a higher crystal perfection than neat PA66.

Keywords: crystallization kinetics; differential scanning calorimetry; nylon 66; solvent precipitation.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Heat flow versus time during isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at the different crystallization temperatures by DSC.
Figure 1
Figure 1
Heat flow versus time during isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at the different crystallization temperatures by DSC.
Figure 2
Figure 2
Plots of log{−ln[1−x(t)]} versus logt at the indicated temperature for isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 2
Figure 2
Plots of log{−ln[1−x(t)]} versus logt at the indicated temperature for isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 3
Figure 3
Relative crystallinity X(t) versus different crystallization time t for isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 3
Figure 3
Relative crystallinity X(t) versus different crystallization time t for isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 4
Figure 4
(1/n)lnk versus 1/Tc for Avrami parameter k deduced from isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 4
Figure 4
(1/n)lnk versus 1/Tc for Avrami parameter k deduced from isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 5
Figure 5
Plots of log tmax versus 1/Tc2ΔT of isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 5
Figure 5
Plots of log tmax versus 1/Tc2ΔT of isothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 6
Figure 6
Heat flow versus temperature during nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at different cooling rates.
Figure 6
Figure 6
Heat flow versus temperature during nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at different cooling rates.
Figure 7
Figure 7
Relative crystallinity X(t) at different crystallization temperatures T in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 7
Figure 7
Relative crystallinity X(t) at different crystallization temperatures T in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 8
Figure 8
Relative crystallinity X(t) at different crystallization times t in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 8
Figure 8
Relative crystallinity X(t) at different crystallization times t in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 9
Figure 9
Plots of log{−ln[1−x(t)]} versus logt for the nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 9
Figure 9
Plots of log{−ln[1−x(t)]} versus logt for the nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 10
Figure 10
Plots of log{−ln[1−X(t)]} versus logt from the Ozawa equation in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 10
Figure 10
Plots of log{−ln[1−X(t)]} versus logt from the Ozawa equation in the process of nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 11
Figure 11
Plots of log Φ versus log t for nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at different values of relative crystallinity.
Figure 11
Figure 11
Plots of log Φ versus log t for nonisothermal crystallization of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC at different values of relative crystallinity.
Figure 12
Figure 12
The plots of ln Φ/T*2 versus 1/T* from the Kissinger method of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 12
Figure 12
The plots of ln Φ/T*2 versus 1/T* from the Kissinger method of (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 13
Figure 13
Polarized optical micrographs for solvent-precipitated nylon 66 anneals at 300 °C for 30 min and slow cooled off (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
Figure 14
Figure 14
WAXS scans for solvent-precipitated (a) PA66-BP, (b) PA66-NU, (c) PA66-FA, (d) PA66-HS and (e) PA66-MC.
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