Structure and property development in poly(p-phenylene terephthalamide) during heat treatment under tension

The evolution of several structural characteristics during isothermal heat treatment of poly(p-phenylene terephthalamide) was studied. In this work, heat treatment was interrupted after different treatment times, with the specimens immediately quenched to room temperature. These specimens were then characterized by tensile testing, wide- and small-angle x-ray scattering, and optical microscopy. Structural parameters obtained from these measurements relate to crystal perfection (via the paracrystalline axial distortion parameter), axial crystallite size, transverse crystallite size, degree of chain misorientation, and degree of pleating. Structural and mechanical parameters were then plotted against heat-treatment time to obtain kinetic isotherms for each parameter. The kinetics of the removal of chain misorientation parallels that of tensile modulus increase under all conditions. Of the other structural parameters, only the kinetics of pleat removal mimics that of modulus change, indicating that pleat removal is the effective cause of increased chain alignment and thereby of increased axial stiffness. ©1995 John Wiley & Sons, Inc.     

On the Glivenko-Cantelli problem in stochastic programming: Mixed-integer linear recourse

Expected recourse functions in linear two-stage stochastic programs with mixed-integer second stage are approximated by estimating the underlying probability distribution via empirical measures. Under mild conditions, almost sure uniform convergence of the empirical means to the original expected recourse function is established.     

Linear complementarity and discounted switching controller stochastic games

The class of discounted switching controller stochastic games can be solved in one step by a linear complementarity program (LCP). Following the proof of this technical result is a discussion of a special formulation and initialization of a standard LCP pivoting algorithm which has, in numerical experiments, always terminated in a complementary solution. That the LCP algorithm as formulated always finds a complementary solution has not yet been proven, but these theoretical and experimental results have the potential to provide an alternative proof of the ordered field property for these games. Numerical experimentation with the reformulated LCP is reviewed.     

N-Chlor-Nylons als Polymerreagentien

Ohne Zusammenfassung     

Characterization,by inverse gas chromatography,of the surface properties of calcium carbonate before and after treatment with stearic acid

Summary The interaction of n-alkanes with stearyl chains chemically fixed on the surface of calcite particles is investigated using inverse gas chromatography. Free enthalpy, enthalpy, entropy of adsorption and dispersive component of the surface free energy are determined. Untreated and stearic acid treated calcites have comparable affinities for the alkanes. However, the differences in adsorption entropies point to different interaction mechanisms: gas-solid adsorption for the untreated calcite and gasliquid interactions for the modified sample. Furthermore, for long chains probes, having more than 8 carbon atoms, the loss in entropy is smaller than for shorter chains. Possibly, long chains are only partially inserted in between the stearyl grafts, thus keeping a higher degree of freedom.