Ultra-drawing

For successful gel-spinning/ultra-drawing two requirements must be fulfilled ... 

P. Smith, P.J. Lemstra, J.P.L. Kjpers, and A.M. Kiel, Ultra-drawing of high molecular weight... 

The importance of pre-structuring the PE before ultra-drawing is shown in Figure 13, which reveals the radically different stress-strain behavior of compression molded UHMW-PE (R) versus solution-crystallized UHMW-PE (S). The compression molded sample contains many chain entanglements from melt crystallization and hence can only be drawn to a maximum draw ratio ( ) of 6 or 7. The solution-crystallized sample was drawable to draw ratios in excess of 70, because of the reduced density of chain entanglements. This sample was a cast PE film, with a mass fiaction 2 % PE in decalin, where residual solvent was extracted prior to... 

P.J. Lemstra, C.W.M. Bastiaansen, S. Rastogi, Basic aspects of solution (Gel)-spinning and ultra-drawing of ultra-high molecular weight polyethylene. Structure Formation in Polymeric Fibers Salem, D. R., Ed. Hanser Munich, 2000, pp. 186-223. 

Smith P, Lemstra PJ. Ultra-drawing of high molecular weight polyethylene cast from solution. Colloid Polym Sci 1980 258(7) 891-894. 

Gel-spinning has gained technical importance because the subsequent ultra-drawing yields particularly high stiffness values. Elastic moduli up to 2 X 10 N m have been obtained for polyethylene for draw ratios of about 100, which comes rather near the theoretical limit given by the stiffness of a bundle of all-trans polyethylene chains E = Zx 10 N m . ... 

Lemstra, P.J., Bastiaansen, C.W.M., and Rastogi, S., Basic Aspects of Solution(Gel)-Spinning and Ultra-Drawing of Ultra-High Molecular Weight Polyethylene , in Structure Formation in Polymeric Fibers, Editor Salem, D.R., Hanser Gardner Publications Inc, 2000. 

If primary control by the enclosure is under consideration, the extra wear and tear on electrode holding equipment by the escaping fume must be taken into account. This potential problem is particularly evident on ultra-high-power (UHP) furnaces where the holding equipment would be constantly exposed to high-temperature flame. As a possible solution, the furnace could be equipped with a roof-mounted water-coiled stub stack, which naturally draws fume from the furnace and into the enclosure. This approach would divert the fume and prevent damage to the electrode equipment. 

Miscibility or compatibility provided by the compatibilizer or TLCP itself can affect the dimensional stability of in situ composites. The feature of ultra-high modulus and low viscosity melt of a nematic liquid crystalline polymer is suitable to induce greater dimensional stability in the composites. For drawn amorphous polymers, if the formed articles are exposed to sufficiently high temperatures, the extended chains are retracted by the entropic driving force of the stretched backbone, similar to the contraction of the stretched rubber network [61,62]. The presence of filler in the extruded articles significantly reduces the total extent of recoil. This can be attributed to the orientation of the fibers in the direction of drawing, which may act as a constraint for a certain amount of polymeric material surrounding them. 

Figure 2.22 Zinc-finger-DNA interactions for PDB IZAA as described in reference 31 and the text. Visualized using The PyMOL Molecular Graphics System and Chem-Draw Ultra, version 10.0. (Printed with permission of Delano Scientific, LLC and CambridgeSoft Corporation.) (See color plate)...

Figure 6.8 A group I intron transition state stabilized by two magnesium ions (PDB IZZN). Visualized using CambridgeSoft Chem3D Ultra 10.0 with notations in Chem-Draw Ultra 10.0. (Printed with permission of CambridgeSoft Corporation.)...

Recently, various techniques that produce highly oriented linear polyethylene with a ultra high modulus (hereafter, referred to as UHMPE) have been developed. In this section, we will examine the structure of the UHMPE that was prepared by highly drawing a dried gel [69]. Even if bulk polyethylene is uniaxially highly drawn by a normal method at a temperature between the Tg and Tm, the phase structure is essentially similar to the undrawn sample. That is, it involves three phases of the crystalline and two noncrystalline phases, although the mass fraction and detailed content of each phase are somewhat different. However, UHMPE samples may have a particular phase structure. 

If large samples of air are taken from the interior of the car, ultra-pure gas must be added to balance the draw-off. 

Methods for the analysis of organic and organometallic compounds are discussed in this chapter. It has become evident that for the analysis of these two classes of compounds, the analyst can draw on a very similar repertoire of analytical techniques with respect to sample preparation, separation, and detection. Chromatographic and, in particular, hyphenated techniques are the workhorses of environmental water analysis. The various formats and technical realizations of mass spectrometers are the most versatile detectors. Their sensitivity and ability to provide structural information at the low and even sub-pg level are an asset and at the same time a prerequisite for (ultra)trace analysis in the aquatic environment. As further significant improvements in detector sensitivity are unlikely, the probable focus of attention in the future will again be on sample preparation. Here, the introduction of new approaches, techniques, and materials for sample preparation can be expected to make a significant impact in this field. 

Air (CDDs) Drawing of approximately 325 m3 of air through quartz fiber filter/polyurethane foam Soxhlet extraction with benzene, volume reduction clean-up using silica, alumina, activated carbon volume reduction addition of [13C12]2,3,7,8-TCDD. HRGC/HRMS MID (EPA TO-9) 1-5 pg/m3 68-140 from ultra pure, filtered air EPA1988g... 

G. Capaccio and I. M. Ward, Ultra-high Modulus Linear Polyethylene through Controlled Modulus Weight and Drawing, Polym. Eng. Sci., 15, 219-224 (1975). 

The difference in drawing behaviour between conventional melt-extruded polymers and ultra-drawable gel-spun polymers is indeed striking (see Fig. 19.19, curves a and b respectively). There is an interesting correlation between the initial concentration of the... 

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