聚氧化乙烯熔體流變特性的研究.pdf

1、中國科學技術(shù)大學碩士學位論文聚氧化乙烯熔體流變特性的研究姓名：方郁野申請學位級別：碩士專業(yè)：材料加工工程指導教師：李良彬2011-05-15Abstract ABSTRACT The behavior of polymer melts is very significant for both rheology theory and industrial processing. Although flow instabilities (m

2、elt fracture) are regarded as the intrinsic property of polymers since the 1960s, their molecular mechanisms are still unclear. Besides, these flow instabilities are usually accompanied by wall slip, which makes the phen

3、omenon more complicated. Since 2006, the particle-tracking velocimetry (PTV) observations by Wang’s group (Akron University) has revealed shear inhomogeneity in entangled polymers either during startup shear (shear bandi

4、ng) or after large deformation (non-quiescent relaxation), which sheds new light on the subject of polymer rheology. So in 2009, the National Science Foundation (USA) supported five-member team to check the phenomenon. I

5、n this work, we combine a home-made high-temperature cone-plate rheometer (the maximum torque is 10 Nm whereas a commercial rheometer typically has 0.2 Nm.) with PTV technique to explore the nonlinear rheological behavio

6、r of a high viscosity poly(ethylene oxide) (PEO) melt. Here, the conditions with and without wall slip are both determined and compared. On smooth metal surfaces, the PEO melts exhibited delayed wall slip after shear ces

7、sation, when the imposed strain was larger than a critical value. In the absence of wall slip suppressed by gluing technique, the PEO melts exhibited internal macroscopic motions after shear cessation, when the imposed s

8、train was larger than a critical value. Both of the critical strain is around unity, which can be estimated by Wang’s theory. The non-quiescent relaxation behavior of entangled melts has only recently been reported once

9、in the literature involving a room temperature melt, and our work is the first PTV observation of non-quiescent relaxation at high temperature. Key Words: poly(ethylene oxide), shear inhomogeneity, shear banding, non-qui