Melting behavior of polypropylene fibers studied by differential scanning calorimetry

Polypropylene fibers produced in a compact-spinning process were studied by differential scanning calorimetry (DSC). With unrestrained fibers, the onset of melting increases with decreasing draw ratio, increasing M_w/M_n, decreasing extrusion temperature, increasing annealing ratio, and increasing draw-down ratio. These trends are discussed in terms of restraints and reorganization. The onset of melting is shifted to lower temperatures as the heating rate increases for all combinations of material and processing parameters, indicating suppressed reorganization. At low draw ratios, the height and width of the endotherm are affected by the spinline stress, and a secondary peak or shoulder is observed on the high temperature side of the main peak. The magnitude of the secondary peak increases with decreasing M_w/M_n, increasing draw ratio, decreasing draw-down ratio, and decreasing heating rate, but its position mainly depends on the heating rate. This indicates that the secondary peak may be due to the melting of structures that have been reorganized during the heating scan. As the draw ratio increases, the melting regime broadens, especially towards lower temperatures, and several maxima emerge on the DSC curve. Reorganization and shrinkage during heating may explain these observations. © 1995 John Wiley & Sons, Inc.     

Use of inert gases in extruded medium density polypropylene foams

Carbon dioxide gas was used as a physical blowing agent to produce medium density polypropylene foam sheets using a single screw extruder. The mechanical properties of the foam were similar in the machine direction and in the transverse direction. A better surface finish and a lower density foam was produced by using a commercial wrapping film as a cap layer. The process conditions and die design data are presented in an attempt to relate to product characteristics.     

Comparison of geophysical methods for sub-surface mapping of faults and fracture zones in a section of the Viggja road tunnel, Norway

Results from site investigations, 2D resistivity, refraction seismic and VLF on a section of tunnel near Trondheim, show that 2D resistivity data are most valuable for interpreting geological structures in the sub-surface. VLF only identifies zones and does not indicate thickness, width or dip direction. The method is also sensitive to technical installations. Refraction seismic is valuable for mapping depth to bedrock, location and width of fracture zones but cannot indicate the depth or dip direction of such zones. With 2D resistivity, the position of a zone is well identified. This method may also provide information on the depth and width of the zone as well as the dip direction. In most cases 2D resistivity clearly identifies zones in the bedrock that can be observed as fault and/or fracture zones in the tunnel. The results described in this paper show a good correlation between the resistivity profiles, mapped structures on the surface and mapped zones in the tunnel.     

Retrieval of total ozone abundances from the ultraviolet region of spectra recorded with an ultraviolet-visible spectrometer

A method is described for deriving total ozone abundances from zenith-sky intensities measured by an UV-visible spectrometer, known as the System of Analysis of Observations at Zenith (SAOZ). Total ozone abundances are determined by comparison of intensity ratios measured at two wavelengths in the UV region with ratios computed with a radiative transfer model. The wavelength pair 320-307 nm was used in this study. Spectra recorded by the SAOZ spectrometer in Oslo (60 degrees N) from the beginning of May 1995 to the end of August 1995 were analyzed, and the results were compared with total ozone measured with a Brewer instrument. The relative difference in derived ozone abundances for the whole period, including days with thin and medium-thick cloud covers, is -0.18 +/- 1.46%. We study the effects of clouds and varying ground albedo on the derived total ozone. Clouds result in an overestimation of the derived total ozone. The error increases with the optical depth tau of the cloud from approximately 2% for an optically thin cloud (tau = 0.5) to approximately 10% for a thick cloud (tau = 50). The ratio between measured intensities at 550 and 350 nm, the so-called color index, can be used as a measure of the cloud optical depth for thin and medium-thick clouds. The effects of thin and medium-thick clouds on the derived ozone abundances can be compensated for by use of an empirical relationship found between the measured color index and the error in the inferred ozone abundances caused by cloud scattering. We also study the influence of changes in the ground albedo and in the ozone profiles on derived total ozone values.     

A hybrid fuzzy logic/constraint satisfaction problem approach to automatic decision making in simulation game models

Possible techniques for representing automatic decision-making behavior approximating human experts in complex simulation model experiments are of interest. Here, fuzzy logic (FL) and constraint satisfaction problem (CSP) methods are applied in a hybrid design of automatic decision making in simulation game models. The decision processes of a military headquarters are used as a model for the FL/CSP decision agents choice of variables and rulebases. The hybrid decision agent design is applied in two different types of simulation games to test the general applicability of the design. The first application is a two-sided zero-sum sequential resource allocation game with imperfect information interpreted as an air campaign game. The second example is a network flow stochastic board game designed to capture important aspects of land manoeuvre operations. The proposed design is shown to perform well also in this complex game with a very large (billionsize) action set. Training of the automatic FL/CSP decision agents against selected performance measures is also shown and results are presented together with directions for future research.     

Nonuniform cooling in multifilament melt spinning of polypropylene fibers: Cooling air speed limits and fiber-to-fiber variations

The cooling of the spinning stage in a commercial compact-spinning line has been studied. A rectangular fiber bundle is extruded from the spinneret and cooled by air entering from one side. The speed of the cooling air is considerably reduced through the fiber bundle. There are practical lower and upper limits for the cooling air entrance speed, corresponding to filament breakage at the leeward and windward sides, respectively. These limits are functions of the material and processing parameters. Due to the nonuniform cooling, fibers sampled at the windward side generally have higher molecular orientation, lower amorphous fraction, higher density, and higher tensile modulus and strength. For most combinations of spinning and material parameters, the structure is either bimodally oriented α-crystalline or uniaxially oriented mesomorphic at all spinneret positions. Fibers with different structure types show opposite windward/leeward side trends with regard to local order and melting behavior. The structure may be mesomorphic at the leeward side and α-crystalline at the windward side, if the average spin-line stress is close to a critical value for orientation-induced crystallization, and the air speed difference across the spinneret is large. The cooling air speed affects the spin-line stress. Hence, the fiber-to-fiber variations due to nonuniform cooling are discussed in terms of the molecular orientation in the melt and the effective time available for arranging molecules into ordered structures. © 1995 John Wiley & Sons, Inc.     

Relationships between the properties of fibers and thermally bonded nonwoven fabrics made of polypropylene

Typical polypropylene fibers for use in light nonwoven fabrics were produced in a full scale compact-spinning line. Molecular weight distribution (MWD), extrusion temperature, draw-down ratio, and draw ratio were varied. The fibers were thermally bonded (welded) into nonwoven fabrics, at different bonding temperatures, using a pilot calender line. The tensile properties of the fabrics are influenced by the MWD and the processing conditions of the fibers, and the effects of these fiber parameters increase with increasing bonding temperature. The fabric strength increases with increasing M_w/M_n, decreasing draw ratio, and increasing extrusion temperature, while in all these cases the fiber strength generally follows the opposite trend. Furthermore, the fabric strength, as well as the fiber strength, have a maximum as a function of draw-down ratio. The tensile properties of the fabrics seem to be governed by the bonding properties of the constituent fibers, not the fiber strength per se. Bond characteristics are discussed in terms of skin-core structures. Some details of the macroscopic fracture mechanisms of fabrics were revealed by scanning electron microscopy and the shape of load-elongation curves. © 1995 John Wiley & Sons, Inc.     

Large increase of Langerhans cells in human skin lymph derived from irritant contact dermatitis

The pharmacokinetic profile of a sulphamonomethoxine-trimethoprim (SMM-TMP) combination was investigated in five horses. The combination was administered intravenously, intramuscularly and orally at a constant dose of 20 mg SMM plus 4 mg TMP kg-1 bodyweight. Following intravenous administration both drugs dispersed rapidly with distribution half-lives of about 12 minutes for SMM and about 18 minutes for TMP. Elimination half-lives for intravenous, intramuscular and oral administration were closely similar, indicating that elimination was independent of administration route. Bioavailability of the drugs in aqueous solution was good: about 72 per cent and 84 per cent for SMM and about 84 per cent and 98 per cent for TMP following intramuscular and oral administration, respectively. It is concluded that SMM-TMP administered orally once a day at 20 mg and 4 mg kg-1 bodyweight, respectively, maintains therapeutic concentrations, whereas twice daily intramuscular administration would be more effective for treating systemic infections in the horse than the once a day regimen usually adopted in veterinary practice.