Synthesis and nonisothermal crystallization kinetic study of semi⁃aromatic polyamide 6T/6I/6

doi:10.19491/j.issn.1001-9278.2022.10.003

Abstract

Abstract:

A semi⁃aromatic polyamide 6T/6I/6 （PA6T/6I/6） was synthesized using a two⁃step method through salt forming and high⁃temperature solution polycondensation. Its nonisothermal crystallization kinetics was investigated by differential scanning calorimetry （DSC）， and its nonisothermal crystallization behaviors of PA6T/6I/6 was studied using the Jeziorny′s method， the Oazawa′s method， and Avrami′s equation modified by the Mo′s method. The results indicated that there were two stages in the crystallization process of PA6T/6I/6， including primary crystallization and secondary crystallization. In the primary crystallization stage， the Avrami index varies from 1.08 to 1.09， resulting in the formation of crystals through heterogeneous nucleation and growth in a one⁃dimensional needle shape. In the secondary crystallization stage， the Avrami index was in the range of 2.13~2.21， leading to the two⁃dimensional sheet growth of crystals. The Ozawa′s method is not suitable for describing the nonisothermal crystallization process of PA6T/6I/6. The modified Avrami′s equation can describe the crystallization process better， with a value of （a） between 0.89 and 0.90 and a value of F（T） between 7.24 and 15.85. The activation energy for the nonisothermal crystallization of PA6T/6I/6 was calculated to be 294.17 kJ/mol using the Kissinger′s equation.

Key words: polyamide, differential scanning calorimetry, non?isothermal crystallization kinetics, crystallization activation energy

CLC Number:

TQ323.6

ZHOU Yang, ZHAO Shikun, ZHAO Biao, LIU Huipeng, LI Jie, CAO Zhiwen, PAN Kai. Synthesis and nonisothermal crystallization kinetic study of semi⁃aromatic polyamide 6T/6I/6[J]. China Plastics, 2022, 36(10): 15-22.

Figures/Tables 14

Fig.1. FTIR curves of PA6T/6I/6

Fig.2. 1H⁃NMR spectrum of PA6T/6I/6

样品	拉伸强度/ MPa	弯曲模量/ GPa	缺口冲击强度/ kJ·m^-2
PA6^①	75	—	5.5
PA6T/6^②	80	—	8
PA6T/66^［8］	92	2.2	2.7
PA6⁃6T/6I^［9］	81	1.9	2.5
PA66/PA6I6T^［10］	97	—	1.7
PA6T/6I/6^①	95	3.6	6.0

Tab.1. Mechanical properties of PA6 and PA6T/6 copolymer

Fig.3. Cooling curves of PA6T/6I/6 at different cooling rates

冷却速率/℃·min^-1	T_o/℃	T_p/℃	T_g/℃	T_m/℃
5	262.47	249.41	116.73	291.32
10	255.83	244.22	116.61	290.64
15	253.07	243.10	116.13	291.74
20	249.24	238.90	117.19	292.31
25	247.30	237.22	114.32	291.89

Tab.2. Nonisothermal crystallization parameters of PA6T/6I/6 at different cooling rates

Fig.4. Melting curves of PA6T/6I/6 at different cooling rates

Fig.5. Relationship between crystallinity Xt and crystallization temperature T

Fig.6. Relationship between crystallinity Xt and crystallization time T

Fig.7. Plot of lg［-lg（1-Xt ）］ versus lgt for non⁃isothermal crystallization process of PA6T/6I/6

ϕ/ ℃·min^-1	n₁	Z_t / min^-ⁿ	Z_c1	n₂	Z_t2 / min^-ⁿ	Z_c2	t_0.5/ min
5	1.09	0.06	0.57	2.21	0.10	0.63	2.55
10	1.08	0.12	0.81	2.18	0.51	0.93	1.19
15	1.09	0.20	0.90	2.13	1.34	1.02	0.75
20	1.08	0.29	0.94	2.15	2.51	1.05	0.57
25	1.08	0.43	0.97	2.19	5.28	1.07	0.41

Tab.3. Kinetic parameters of non⁃isothermal crystallization of PA6T/6I/6

Fig.8. Plot of lg［-lg（1-Xt ）］ versus lgϕ for non⁃isothermal crystallization process of PA6T/6I/6

Fig.9. Plot of lnϕ versus lnt for the non⁃isothermal crystallization process of PA6T/6I/6

X	0.2	0.3	0.4	0.5	0.6	0.7	0.8
F（T）	7.24	8.91	10.23	11.48	12.88	14.45	15.85
a	0.89	0.89	0.88	0.89	0.89	0.90	0.90

Tab.4. Values of F（T） and a for PA6T/6I/6 at different crystallinity

Fig.10. Plot of ln（ϕ/Tp2） versus 1/Tp for PA6T/6I/6

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