Li-Hui Wang

Compatibility and transesterification in binary polymer blends

Abstract Polyester blends have been intensively studied both for industrial application and for academic interest. Properties of these blends are related to their miscibility. It has been found that the miscibility reported for certain blends has been influenced by transesterification. For other polyester pairs miscibility is caused directly and only by interaction of components. The miscibility for a variety of polyester blends, including polyester liquid crystals, is discussed and the relationship between the miscibility and transesterification in the individual blend pairs is detailed in this review.

Uniaxial Extension and Order Development in Flexible Chain Polymers

Abstract It is well known that the highest elastic moduli reported for linear poly-mers are generally much smaller than their theoretical values. This has been shown particularly by Nakamae and coworkers [1]. For a range of poly-mers they have summarized their crystal moduli determined by x-ray dif-fraction as measured in the stiffest direction, parallel to the polymer chain axis. These values on crystals approximate the ultimate polymer moduli; they therefore may be compared with the much lower presently reported values for the conventional structure of these polymers (Fig. 1). This figure shows that most polymers, including those with rigid backbone chains, have tensile moduli far below those of their crystalline lattice in the chain direction. The exceptions are specially drawn ultrahigh molecular weight polyethylene (UHMW PE), which in PE parlance is generally considered to mean molecular weight above one million, and for isotactic polypropyl-ene that also has been drawn to tensile moduli that approac...

The characterization and properties of nylon 13,13

Abstract The physical properties of the nylon with the longest number of methylene segments, nylon 13,13 have been characterized. Studies are reported of thermal analysis, X-ray scattering and for mechanical properties including hardness. The crystal of nylon 13,13 has been found to have a monoclinic form with a = 4.9 A , b = 9.22 A , c = 34.40 A and β = 121.08°. Also, studies were carried out on the mechanical properties of nylon 13,13 that had been uniaxially drawn by solid-state extrusion at 125 and 135°C. The highest draw ratio obtained was 4.5. The maximum melting point, heat of fusion and amorphous density were estimated to be ⩾ 183°C, 230 J g−1 and 1.01 g cm−3, respectively. The crystallinity, melting temperature and tensile modulus increased with draw ratio. The glass transition temperature of the undrawn polymer was 56°C. For the sample with a draw ratio of 4.0, the tensile modulus and the X-ray crystal orientation function reached 2 GPa and 0.94, respectively.