Font Size: a A A

Study On Preparation Of PH-sensitive Porous Hollow Gel Fiber Based On Ultrahigh Molecular Weight Polyacrylonitrile And Its Structure And Properties

Posted on:2002-03-02Degree:DoctorType:Dissertation
Country:ChinaCandidate:X Y ShenFull Text:PDF
GTID:1101360095953854Subject:Materials Science and Engineering
Abstract/Summary:PDF Full Text Request
As an important smart materials, pH-sensitive polymer gels have received increasing attention in materials research communities. However, most of the polymer gels studied so far are bulk samples, and some properties of these gels, such as mechanical property, response rate, operating property etc, are not good enough. For a few fiber samples, it is not easy to pump the stimulus medium. Specially, there is not micro-porous structure that is highly desirable for chemi-machinical systems in many samples. Therefore, the application of these gel polymers is largely limited. The purpose of this project is attempted to resolve the above problems and develop a kind of novel porous hollow gel fibre(PHGF) which have good mechanical property, pH-sensitivity and operating property to accelerate the practical application of the smart polymer gels.In this paper, a new method making the PHGF indicated above has firstly be presented, by which porous hollow fiber(PHF) is prepared with ultrahigh molecular weight polyacrylonitrile(UHMW-PAN) by gel-spinning, and PHGF is made by oxidation and saponification, using PHF as the precursor.The main achievements include the followings:1.A series of UHMW-PAN are prepared by water-phase polymerization. They are characterized by FTIR, GPC, NMR, X-ray diffraction and TGA method. It is concluded that the product is polyacrylonitrile homopolymer with viscometric average molecular weight Mv above 100#104, narrow molecular weight distribution, and head-tailor structure. Its regularity and thermal stability are better than common polyacrylonitrile(C-PAN). Crystallinity increases with Mv. Therefore, the UHMW-PAN is a real material for making the PHF with high strength.2.The rheological behavior and spinnability of UHMW-PAN/DMSO semi-dilute solution7are studied with capillary rheometer. It can find that flow curves move upward, n decreases, flow ability and spinnability get worse with the increase in Mv and concentration, the decrease in temperature.The energy for viscous flow activation is 18.71kJ/mol, ln η=-6.80+2.25×(l/T×103),η0=KC5.1M5 .7.The maximum relaxation time is two order higher than C-PAN/DMSO concentrated solution, so when the temperature is below 130℃, the first Newtonian zone does not appear in the flow curves. When Mv is 1.29× 106, concentration is 3%, temperature above 110×, the solution has better flow ability, spinnability and extrusion stability.3.The technology of preparing PHF is studied in details. The experiment results indicate that PHF "produced by gel-spinning has better strength at break and flexibility. Molecular weight, concentration of solution(C), air gap length(L) and straw ratio(R) have effects on the mechanical property of PHF. The suitable spinning techniques is: gel-spinning, Mv is 1.29×106, C is 3%, L is 3cm, and R is 14.The UHMW-PAN based PHF is characterized by X-ray diffraction, SEM, TGA, S-S curve. It shows that the crystallinity and crystalline size of UHMW-PAN based PHF are larger than C-PAN, the surface is smooth and dense, and the walls among the finger-like pores are thick and dense, the tenacity and thermal stability are also very well. These suggest that the PHF is suitable for the precursor of the PHGF.4.The preparation techniques of UHMW-PAN based porous oxidation fiber (PHOF) are firstly studied in details. It shows that oxidation temperature and time have great effects on the degree of ring formation for PHF. Compared with C-PAN based solid fibers, the oxidation temperature should be below (<240℃), and oxidation time should be short(<2h). UHMW-PAN based PHOF is characterized by FUR, X-ray diffraction, SEM and S-S curve. It is confirmed that during oxidation, C=N is changed into C=N, crystalline structure is destroied, planar networks structure is formed with pyridine rings and cyan groups as a cross linker. The morphological structure is similar to the precursor, but its surface is denser than C-PAN based PHGF, the walls among finger-like pores are thickening. These suggest that the PHGF is suitable to prepare the PHG...
Keywords/Search Tags:ultrahigh molecular weight polyacrylonitrile, porous, hollow, gel fiber, pH-sensitivity
PDF Full Text Request
Related items