Transcrystallization of syndiotactic polystyrene

• Main Authors: Chao-Chen Chen, 陳照程
• Other Authors: Chi Wang
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/96369366427275894540

碩士 === 元智大學 === 化學工程研究所 === 87 === ABSTRACT This experiment, using polarized optical microscope equipped with hot stages, aims at measuring the growth rates of different crystal types of s-PS matrix (Mw=ca. 200kg/mol) in the composite which is formed by high modulus carbon fibers, and the state of growth of the crystal is detected accordingly. Within the range of crystallization temperatures(240~276℃) , not only the transcrystallization and the morphology of spherulite are observed, but the existence of the morphology of axialite crystals is also found; therefore, the relation between the appearance of the morphology of axialite crystals and the crystallization temperatures will be analyzed in the study as well. In addition, the observation of negatively birefringent spherulites is also an important accomplishment. Comparing with other types of crystals in the system, the growth rate of negatively birefringent spherulites is much lower than that of other crystals. In accordance with Marand's method[48, 49], equilibrium melting temperature of positively birefringent spherulites and negatively birefringent spherulites shows separately 312℃ and 295℃. Based on the LH theory, the fold surface free energy e of positively birefringent spherulites is 40.84erg/cm2, while that of negatively birefringent spherulites is 6.44 erg/cm2. Besides, the works of chain folding q of positively birefringent spherulites and negatively birefringent spherulites present 7.47 and 3.69kcal/mole, respectively. Meanwhile, using the induction time, the interfacial free energy difference function of s-PS on carbon fibers is proved to be 0.61erg/cm2. Furthermore, based on general optics principles and using a polarized optical microscope, it is verified that the third endothermic peak (the highest temperature endothermic peak), When heating using DSC, is the operation of re-meltting after the crystals are recrystallized. At this time, from FTIR, the influence of crystallization temperature on crystal forms is concluded: the higher crystallization temperature is used, the more restriction of development the -form will encounter. Additionally, in order to compare the nucleation ability of s-PS on different fibers (Kevlar, high strength carbon, PTFE, PBO, glass fiber and copper wire) analyzed, different fibers are added to s-PS matrix. The result of this experiment manifests that no phenomenon of transcrystallization is shown on high strength carbon fibers, glass fibers and copper wires without acid treatment.