Shenghui Chen

Copolymer Structure and Properties of Aromatic Polysulfonamides

A series of aromatic polysulfonamides with various monomer ratios of 4,4′-diaminodiphenylsulfone (p-DDS) and 3,3′-diaminodiphenylsulfone (m-DDS) were synthesized to investigate the relationship between copolymer composition and their properties. The copolymer composition was determined from nuclear magnetic resonance (NMR). It was found that the copolymer composition of the polysulfonamides varied little from the monomer ratio; thus, similar reactivity of the two diaminodiphenylsulfones was shown by the results. From the analysis of the thermal properties of the polysulfonamides, high thermal stability of the copolymers was shown both in N2 and air and the decomposition temperature exhibited little dependence on the copolymer composition. However, the glass transition temperatures (Tg ) decreased obviously with increasing m-DDS segments, which is helpful to improve the solubility and spinnability of these polysulfonamides.

The combined effect of heat-draw ratios and residence time on the morphology and property of aromatic copolysulfonamide fibers

The wet-spun aromatic copolysulfonamide (co-PSA) fibers were heat-drawn at different ratios and then characterized by tensile testing, wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). The results showed that the tenacity of co-PSA fibers did not increase monotonously with the draw ratios and a maximal value of tenacity and initial modulus was observed as the heat-draw ratio increased. Accordingly, the large crystalline size, content of mesophase and crystal phase, as well as long period and fibril length, were corresponding to the maximum tenacity of the heat-drawn fibers. This suggested that the residence time of the co-PSA fibers, during which it stayed in the heat tube, could not be neglected when the draw ratios changed. A more perfect structure could be formed with a favourable draw ratio and residence time.

Properties and phase morphology of cellulose/aromatic polysulfonamide alloy fibers regulated by the viscosity ratio of solution

Cellulose/aromatic polysulfonamide (PSA) alloy fibers with good flame retardant properties were successfully prepared by changing the viscosity ratio of cellulose and PSA solutions. To reduce the content of PSA in the alloy fibers, cellulose and PSA with different molecular weight were adopted to prepare the alloy fibers. From the results of the limiting oxygen index(LOI) and the self-extinguishing time away from the flame, it was shown that the flame retardant properties of the alloy fibers were improved as the viscosity of PSA/[BMIM]Cl solution was lowered. The contact angle and the water retention values of the alloy fibers showed that the moisture absorption was strengthened with the addition of cellulose. To verify the properties of the alloy fiber, phase morphologies were characterized by laser scanning confocal microscope (LSCM). An analogous “sheath-core” structure in the cross section of the alloy fibers was shown when the viscosity of PSA/[BMIM]Cl solution was lower enough than that of cellulose/[BMIM]Cl solution. The lower viscosity PSA component was observed to migrate to the outer layer of the fiber, while the higher viscosity cellulose remained within the inner core of the fiber during the spinning process. This behavior improved the flame retardant properties of the alloy fibers at certain weight ratios. This work provides an effective way to prepare cellulose/PSA alloy fibers with improved flame retardancy, hygroscopic behavior, and mechanical strength by the regulating the phase morphology.

Rheological Characterization of Poly(3,3′-Diaminodiphenylsulfone Terephthaloylchloride) Solutions in Dimethylsulfoxide

Steadyshear and oscillatory shear rheological measurements were performed to characterize the solution rheological behavior of poly(3,3′-diaminodiphenylsulfone terephthaloylchloride) (P(3,3′-DDS-TPC)) in dimethyl sulfoxide (DMSO). The effects of temperature, concentration, and weight-average molar mass () on the rheological properties were investigated. From the temperature dependence of zero-shear viscosity, the flow activation energies, Eη, of P(3,3′-DDS-TPC)/DMSO solutions were calculated. Both the overlap concentration, C*, and the entanglement concentration, Ce, were determined from the concentration dependence of the specific viscosity ηsp. All the P(3,3′-DDS-TPC) solutions, we studied, can be separated into three regimes: the dilute, semidilute-unentangled, and entangled regime with slopes of 1, 1.3, and 3.9, of concentration versus ηsp plots, respectively, which are consistent with scaling predictions for flexible polymers in a good solvent.