Isothermal crystallization behavior of polypropylene in solution

China Plastics ›› 2023, Vol. 37 ›› Issue (1): 13-17.DOI: 10.19491/j.issn.1001-9278.2023.01.003

• Materials and Properties • Previous Articles Next Articles

Isothermal crystallization behavior of polypropylene in solution

ZHANG Hengyuan(), LIU Jianye(), WANG Shaojie, XU Yaohui, ZHANG Shijun

SINOPEC（Beijing） Research Institute of Chemical Industry Co，Ltd，Beijing 100013，China

Received:2022-11-04 Online:2023-01-26 Published:2023-01-26

Abstract

Abstract:

The isothermal crystallization behaviors of polypropylene （PP） in two different solvents were analyzed by using differential scanning calorimeter （DSC）， and its isothermal crystallization kinetics was studied by using the Avrami's equation. The results indicated that the crystal growth rate decreased with an increase in crystallization temperature. Meanwhile， the reduction of nucleation constant （K_g） and end surface free energy （σ_e） indicated that the crystallization rate of PP in solution was higher than that of pure PP according to the Lauritzen–Hoffman's theory.

Key words: polypropylene, solution crystallization, isothermal crystallization, secondary nucleation theory

CLC Number:

TQ325.1⁺4

ZHANG Hengyuan, LIU Jianye, WANG Shaojie, XU Yaohui, ZHANG Shijun. Isothermal crystallization behavior of polypropylene in solution[J]. China Plastics, 2023, 37(1): 13-17.

Figures/Tables 8

Fig.1. Evolution of heat flow of PP during isothermal crystallization in n⁃hexane and xylene

Fig.2. Evolution of relative crystallinity of PP during isothermal crystallization in n⁃hexane and xylene

Fig.3. The relationship between log［-ln（1-X（t））］ and logt during isothermal crystallization of PP in n⁃hexane and xylene

溶剂	T	n	k/min^-n	t_1/2 /min
正己烷	75	1.261 03	0.321 6	1.145
	77.5	1.154 97	0.092 22	3.786
	80	1.792 23	0.028 7	5.911
	82.5	1.921 74	0.016 34	6.899
	85	1.833 15	0.006 092	13.231
二甲苯	60	1.047 55	3.889	0.192 7
	65	1.202 69	3.174	0.282 2
	70	1.022 62	0.764 1	0.909 0
	75	1.176 87	0.215 4	2.699 7
	80	1.779 76	0.015 94	8.326 3

Tab.1. Isothermal crystallization kinetic parameters of PP in n⁃hexane and xylene

Fig.4. DSC heating thermograms after isothermal crystallization of PP in n⁃hexane and xylene

Fig.5. Determination of equilibrium melting point of PP in n⁃hexane and xylene by Hoffman Weeks equation

Fig.6. U*R(Tc-T∞-lnt1/2) as a function of （1/Tc）ΔT·f of PP in n⁃hexane and xylene

T m 0

K_g/×10⁵ K²

σσ_e/

erg²·cm^-4

σ_e/

erg·cm^-2

14.4 %正己烷

样品

T m 0

/℃

K_g/×10⁵ K²

σσ_e/

erg²·cm^-4

σ_e/

erg·cm^-2

14.4 %正己烷

132.49

2.79

793.1

60.62

12 %二甲苯

124.33

2.65

769.0

58.78

Tab.2. Kg， σσe and σe values calculated by the Lauritzen⁃Hoffman equation

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