聚全氟乙丙烯中空纤维膜的制备及性能

doi:10.7503/cjcu20170053

摘要/Abstract

摘要：

以聚全氟乙丙烯(FEP)为成膜聚合物, MT-Ⅱ型复合粉为致孔剂, 邻苯二甲酸二辛酯(DOP)为稀释剂, 采用熔融纺丝拉伸法制备了FEP中空纤维膜, 研究了其耐酸碱等性能. 结果表明, FEP中空纤维膜的表面具有由拉伸孔、界面孔及溶出孔组成的多重孔结构, 而其横截面为均匀分布的海绵状孔结构. FEP中空纤维膜经质量分数为25%的硫酸水溶液和25%的氢氧化钠水溶液分别处理60 d后, 膜的化学结构未发生变化, 而且平均孔径增大, 孔径分布变窄, 断裂强度保持率分别在86.8%及80.8%以上, 耐酸碱性明显优于商业化聚偏氟乙烯(PVDF)中空纤维膜, 显示出优异的化学稳定性及良好的热稳定性.

关键词: 聚全氟乙丙烯中空纤维膜, 熔融纺丝, 化学稳定性, 高纯水通量

Abstract:

Poly(tetrafluoroethylene-co-hexafluoropropylene)(FEP) hollow fiber membranes(HFMs) were prepared by melt spinning method with FEP as polymer matrix, water solubility composite powder as pore-forming agent and dioctyl phthalate(DOP) as diluent. The effects of different concentrations of acid and alkali on the structure and properties of FEP HFMs were studied. The results show that the prepared FEP HFMs have a microporous structure with stretched pores, interface microporous and dissolved microporous, and the sponge-like microporous structure is evenly distributed on the cross-section. After 60 d immersed in 25% NaOH and H₂SO₄ solution, the chemical structure of the membranes has been unaffected, while the average pore size becomes larger and the pore size distribution narrows. The retention rates of break strength reach 86.8% and 80.8%, respectively. The acid and alkali resistance study indicates that the FEP HFMs have excellent chemical and thermal stability compared to commercial PVDF HFMs.

Key words: Poly(tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membrane, Melt spinning, Chemical stability, High pure water flux

中图分类号:

O632.51

TrendMD:

游彦伟, 肖长发, 王纯, 黄庆林, 陈明星, 黄岩. 聚全氟乙丙烯中空纤维膜的制备及性能. 高等学校化学学报, 2017, 38(9): 1678.

YOU Yanwei, XIAO Changfa, WANG Chun, HUANG Qinglin, CHEN Mingxing, HUANG Yan. Preparation and Properties of Poly(tetrafluoroethylene-co-hexafluoropropylene) Hollow Fiber Membranes^†. Chem. J. Chinese Universities, 2017, 38(9): 1678.

图/表 19

Fig.1 Schematic diagram of melt spinning process

Fig.2 Schematic diagram of pure water flux testing instrument

Fig.3 Morphologies of untreated FEP hollow fiber membranes(M0)(A) Cross section; (B) partial enlargement of cross section; (C) inner surface; (D) outer surface.

Fig.4 Schematic diagram of stretched pores formation process of FEP hollow fiber membranes

Fig.5 SEM images of FEP hollow fiber membranes immersed by 25% NaOH for 30 d(sample N3, A—C) and 60 d(sample N4, D—F)(A) and (D) Outer surface; (B) and (E) inner surface; (C) and (F) cross section.

Fig.6 SEM images of FEP hollow fiber membranes immersed in 10%(A—C) and 25%(D—F) H2SO4 for 30 d (A, D) Outer surface; (B, E) inner surface; (C, F) cross section.

Fig.7 SEM images of FEP hollow fiber membranes(sample H4) immersed in 25% H2SO4 for 60 d (A) Outer surface; (B) inner surface; (C) cross section.

Fig.8 EDX of FEP hollow fiber membranes (A) M0; (B) N4; (C) H4.

Fig.9 FTIR spectra of FEP hollow fiber membranes immersed in 25% NaOH(A) and 25% H2SO4(B) (A) a. M0; b. N2; c. N4. (B) a. M0; b. H2; c. H4.

Fig.10 DSC curves of M0(a), N4(b) and H4(c)

Fig.11 TG curves of M0(a), N4(b) and H4(c)

Fig.12 DMA curves of M0(a), N4(b) and H4(c)

Fig.13 Pore size distribution of M0, N2, N4, H2 and H4

Table 1 Minimum and average pore diameter of FEP hollow fiber membranes

Sample	Pore diameter_min/μm	Pore diameter_avg/μm
M0	0.3289	0.5468
N2	0.7896	1.0970
N4	0.9913	1.3591
H2	0.8533	1.1844
H4	1.1164	1.5201

Fig.14 Water contact angle of M0(A), N4(B) and H4(C)

Fig.15 Pure water flux of FEP hollow fiber membranes after NaOH(A)/H2SO4(B) treatment (A) a. N1; b. N2; c. N3; d. N4; e. M0. (B) a. H1; b. H2; c. H3; d. H4; e. M0.

Fig.16 Effect of acid and alkali solutions on rejection ratio of carbonic ink by FEP hollow fiber membranes

Table 2 Mechanical properties of hollow fiber membranes

Sample	Stress/MPa	Strain(%)	Stress retention ratio(%)	Sample	Stress/MPa	Strain(%)	Stress retention ratio(%)
M0	5.01	44.5	100	PVDF-0	4.98	84.3	100
N4	4.35	12.2	86.8	PVDF-H	3.11	30.9	62.4
H4	4.05	12.2	80.8	PVDF-N		1.9

Fig.17 External morphologies of M0(A), N4(B), H4(C), PVDF-O(D), PVDF-N(E) and PVDF-H(F)

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