In this study, the effect of sintering conditions including manner, temperature and duration on properties of polytetrafluoroethylene (PTFE) hollow fibre membrane fabricated by extrusion method was intensively investigated. Different from un-sintered and relaxed sintered, the fixed sintered PTFE hollow fibre membrane was observed to generate a uniform ‘fibril–node’ porous structure and a main crystal transformation to folded chain crystal with smaller size. Consequently, it was found that for fixed setting sintering, both temperature increase from 340°C to 400°C and duration prolongation obviously improved pore size, ethanol permeation performance and mechanical strength. Additionally, the test results revealed that the membrane sintered below virgin melting point (350°C) had a noticeable higher porosity but poorer ethanol permeation performance that could be primarily attributed to increased ratio of closed pore. The sintering condition exhibited evident influence on PTFE hollow fibre membrane thermal stability, though it showed no alteration to the thermal decomposition of PTFE. The obtained PTFE hollow fibre membrane was tested to evaluate their vacuum membrane distillation (VMD) performances. It was found that PTFE membrane from lower sintering temperature delivered a better salt rejection; on the other hand, the permeate flux was improved by increased vacuum pressure during VMD operation.
PengNWidjojoNSukitpaneenitP. Evolution of polymeric hollow fibers as sustainable technologies: past, present, and future. Prog Polym Sci2012; 37: 1401–1424.
2.
AhnYTHwangYHShinHS. Application of PTFE membrane for ammonia removal in a membrane contactor. Water Sci Technol2011; 63: 2944–2948.
3.
LiJGuanYChengF. Treatment of high salinity brines by direct contact membrane distillation: effect of membrane characteristics and salinity. Chemosphere2015; 140: 143–149.
4.
NittamiTHitomiTMatsumotoK. Comparison of polytetrafluoroethylene flat-sheet membranes with different pore sizes in application to submerged membrane bioreactor. Membranes2012; 2: 228–236.
5.
YamazakiNNaganumaKNagaiM. Preparation of W/O (water-in-oil) emulsions using a PTFE (polytetrafluoroethylene) membrane - A new emulsification device. J Dispersion Sci Technol2003; 24: 249–257.
6.
ZhangSLiQLiuY. Polytetrafluoroethylene (PTFE)/carbon black (CB) microporous membranes produced from PTFE/CB composite particles prepared by heterocoagulation process. High Perform Polym2016; 29: 104–112.
7.
ShenXDingWZhaoY. Effect of copolymer concentration on the structure and permeability of temperature-sensitive poly(vinylidene fluoride) hollow fiber membrane. High Perform Polym2013; 26: 357–363.
8.
FengCYKhulbeKCMatsuuraT. Recent progresses in polymeric hollow fiber membrane preparation, characterization and applications. Sep Purif Technol2013; 111: 43–71.
9.
YuYLiuSWangY. Asymmetric membranes prepared with trifluoromethylphenylated poly(ether ether ketone) for gas separation. High Perform Polym2014; 27: 10–18.
10.
FrickASichDHeinrichG. Relationship between structure and mechanical properties of melt processable PTFE: influence of molecular weight and comonomer content. Macromol Mater Eng2013; 298: 954–966.
AriawanABEbnesajjadSHatzikiriakosSG. Preforming behavior of polytetrafluoroethylene paste. Powder Technol2001; 121: 249–258.
13.
OchoaI. Paste extrusion of polytetrafluoroethylene (PTFE) fine powder resin: The effects of processing aid physical properties. PhD Thesis, University of British Columbia, Canada, 2006.
14.
PatilPDFengJJHatzikiriakosSG. An analytical flow model for PTFE paste through annular dies. AlChE J2006; 52: 4028–4038.
15.
KitamuraTKurumadaKTanigakiM. Formation mechanism of porous structure in polytetrafluoroethylene (PTFE) porous membrane through mechanical operations. Polym Eng Sci1999; 39: 2256–2263.
16.
Ranjbarzadeh-DibazarAShokrollahiPBarzinJ. Lubricant facilitated thermo-mechanical stretching of PTFE and morphology of the resulting membranes. J Membr Sci2014; 470: 458–469.
17.
LiuGCGaoCJLiXM. Preparation and properties of porous polytetrafluoroethylene hollow fiber membrane through mechanical operations. J Appl Polym Sci2015; 132: 42696.
18.
KitamuraTOkabeSTanigakiM. Morphology change in polytetrafluoroethylene (PTFE) porous membrane caused by heat treatment. Polym Eng Sci2000; 40: 809–817.
19.
MoriokaTKakiageMYarnanobeT. Oriented crystallization induced by uniaxial drawing from poly(tetrafluoroethylene) melt. Macromolecules2007; 40: 9413–9419.
20.
LehnertRJHendraPJEverallN. Comparative quantitative study on the crystallinity of poly(tetrafluoroethylene) including Raman, infra-red and F-19 nuclear magnetic resonance spectroscopy. Polymer1997; 38: 1521–1535.
21.
LiNNXiaoCF. The effect of stretch on multi-pore-structure of ultrahigh molecular weight polyethylene/SiO2 hybrid hollow fiber membranes. High Perform Polym2010; 22: 820–833.
22.
HuangQXiaoCHuX. Fabrication and properties of poly(tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membranes. J Mater Chem2011; 21: 16510.
23.
HuangQXiaoCHuX. Preparation and properties of polytetrafluoroethylene/CaCO3 hybrid hollow fiber membranes. J Appl Polym Sci2012; 123: 324–330.
24.
OteroJAMazarrasaOVillasanteJ. Three independent ways to obtain information on pore size distributions of nanofiltration membranes. J Membr Sci2008; 309: 17–27.
25.
ChenY. Investigation of test method for porous poly(vinylidene fluoride) hollow fiber membrane pore size and pore size distribution. Master Thesis, University Tianjin Polytechnic, China, 2003.
26.
LeiCWangXFangQ. Space charge distribution and crystalline structure in quenched polytetrafluoroethylene. Eur Polym J2007; 43: 4523–4529.
27.
KostrominaSVZubovYAShirinaNG. A structural investigation of the sintering of raw polytetrafluoroethylene. Polym Sci USSR1990; 32: 388–394.
28.
PucciarielloRVillaniV. Phase behavior at low temperature of poly(tetrafluoroethylene) by temperature-modulated calorimetry. J Fluorine Chem2004; 125: 293–302.
29.
StarkweatherHW. The effect of heating rate on the melting of polytetrafluoroethylene. J Polym Sci Pol Phys1985; 23: 1177–1185.
30.
SuwaTSeguchiTTakehisaM. Effect of molecular-weight on crystalline-structure of polytetrafluoroethylene as-polymerized. J Polym Sci Pol Phys1975; 13: 2183–2194.
31.
MalkinAIKiselevMRKlyuevVA. Effect of mechanical activation on the thermal stability of polytetrafluoroethylene powder. Russ J Phys Chem A2011; 85: 1528–1532.
32.
GangulyRLesserAJ. Mechanism and kinetics of ultra-high molecular weight polytetrafluoroethylene sintering. J Appl Polym Sci2014; 131: 40967.
33.
JordanJLSiviourCRFoleyJR. Compressive properties of extruded polytetrafluoroethylene. Polymer2007; 48: 4184–4195.
34.
EbnesajjadS.. Properties of tetrafluoroethylene homopolymers. In: WoishnisW (eds) Fluoroplastics. Oxford: Elsevier, 2000, pp. 257–280.
35.
WangFZhuHZhangH. Effect of surface hydrophilic modification on the wettability, surface charge property and separation performance of PTFE membrane. J Water Process Eng2015; 8: 11–18.
36.
HambirSSJogJPNadkarniVM. Strength development in powder processing of poly(tetrafluoroethylene). Polym Eng Sci1994; 34: 1065–1069.
37.
ZhuGYuanQHock YeoJ. Thermal treatment of expanded polytetraflu-oroethylene (ePTFE) membranes for reconstruction of a valved conduit. Biomed Mater Eng2015; 26(Suppl 1): S55–S62.
38.
LiMZhangWWangC. Melt processability of polytetrafluoroethylene: effect of melt treatment on tensile deformation mechanism. J Appl Polym Sci2012; 123: 1667–1674.
39.
JiangZGuoZPuC. Preparation and properties of melt-spinning fluorinated ethylene propylene fibres. High Perform Polym2017; 29(4): 476–483.
40.
EndoRKanamotoT. Superdrawing of polytetrafluoroethylene virgin powder above the static melting temperature. J Polym Sci Pol Phys2001; 39: 1995–2004.
41.
ZhuHWangHWangF. Preparation and properties of PTFE hollow fiber membranes for desalination through vacuum membrane distillation. J Membr Sci2013; 446: 145–153.
