Effect of heat treatment of polyacrylonitrile powders on its membrane structure and properties

doi:10.19491/j.issn.1001-9278.2025.09.004

Abstract

Abstract:

In this study， the effects of thermal treatment on polyacrylonitrile （PAN） powder and its subsequent impact on membrane properties were investigated. PAN powders were heat⁃treated under air/vacuum conditions， enabling the preparation of a series of PAN membranes. The thermal treatment promoted both intramolecular and intermolecular cross⁃linking while facilitating the formation of hydrophilic imide structures. This modification effectively exhibited the phase separation rate of PAN solutions in water， yielding membranes with enhanced hydrophilicity and density. Optimal performance was achieved with membranes prepared from PAN powders treated at 140 °C for 2 h in air. The resulting 9 wt% PAN film presented a water contact angle of 47 ° （4.8 ° reduction） and dry film tensile strength of 5.591 MPa （132 % increase） compared to untreated controls. Furthermore， these membranes demonstrated excellent separation performance， with water flux reaching 1 500 L/（m²·h） and n⁃hexadecane rejection of 99.4 %. These findings highlight the significant potential of thermal pretreatment for improving PAN membrane properties for separation applications.

Key words: polyacrylonitrile membrane, heat treatment, crosslink, iminoester

CLC Number:

TQ320

LIU Wei, PEI Wenyu, FU Zhongyu. Effect of heat treatment of polyacrylonitrile powders on its membrane structure and properties[J]. China Plastics, 2025, 39(9): 18-25.

Figures/Tables 14

热处理时间/h	120 ℃	130 ℃	140 ℃	150 ℃
0	6 %/9 %/12 %/15 %	6 %/9 %/12 %/15 %	6 %/9 %/12 %/15 %	6 %/9 %/12 %/15 %
0.5	9 %	9 %	9 %	9 %
1	9 %	9 %	9 %	9 %
2	6 %/9 %/12 %/15 %	6 %/9 %/12 %/15 %	6 %/9 %/12 %/-	6 %/9 %/12 %/-

Tab.1. Heat treatment conditions and PAN concentration of film forming samples

Fig.1. Preparation process of polyacrylonitrile film and oil⁃in⁃water emulsion

Fig.2. Change curves of the visco⁃average molecular weight of PAN under different heat treatment conditions

Fig.3. Infrared analysis curve of heat treated PAN

Fig.4. Intramolecular and intermolecular cross⁃linking of PAN

Fig.5. Nuclear magnetic hydrogen spectrum of PAN powder

Fig.6. Viscosity curve of cast membrane liquid

Fig.7. SEM photo of the sample film with 15 % casting liquid concentration

Fig.8. SEM photo of the sample film with 12 % casting liquid concentration

Fig.9. SEM photo of the sample film with 9 % casting liquid concentration

Fig.10. The pure water flux， retention rate， porosity and average pore size of some sample films

Fig.11. The water contact angle of film formation at PAN concentration of 9 %

Fig.12. Test of film resistance to pollution at PAN concentration of 9 %

样品	拉伸强度/MPa	弹性模量/MPa	断裂伸长率/%
PAN	2.413	178.334	8.623
PAN⁃120 ℃⁃0.5h	2.524	202.513	8.127
PAN⁃120 ℃⁃1 h	2.714	212.461	6.993
PAN⁃120 ℃⁃2 h	3.287	242.825	5.762
PAN⁃130 ℃⁃0.5 h	2.776	231.725	6.312
PAN⁃130 ℃⁃1 h	3.352	240.512	6.175
PAN⁃130 ℃⁃2 h	4.523	322.624	4.835
PAN⁃140 ℃⁃0.5 h	3.970	218.735	5.558
PAN⁃140 ℃⁃1 h	4.821	274.694	3.077
PAN⁃140 ℃⁃2 h	5.591	363.047	3.019
PAN⁃150 ℃⁃0.5 h	4.125	264.131	4.475
PAN⁃150 ℃⁃1 h	5.225	383.519	2.854
PAN⁃150 ℃⁃2 h	5.854	404.617	2.154

Tab.2. The mechanical properties of 9 % PAN film are treated under air

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