Isotactic pressing

HIP hot isotactic pressing HVAC heating, ventilation, and air condi-... 

Isostatic molding, 18 300 Isostatic refractory pressing, 21 504 Isostearic acid, physical properties, 5 35t Isotachophoresis, 9 738, 742, 748 Isotacticity, of polypropylene, 20 529 Isotactic PB resins, thermal properties of, 20 417... 

The effect of heterogeneous nucleation on the crystallization of isotactic polypropylene from the melt can be easily established as follows. A small amount of powdered polypropylene is well mixed with about 0.1 wt% of sodium benzoate in a mortar or by means of an analytical mill. Some of the mixture is transferred with a spatula to a microscope slide and melted at about 250 °C on a hot block. A cover slip is pressed on to the melt with a cork to obtain as thin a film as possible.The sample is held at 200-250 °C for some minutes and then allowed to crystallize at about 130 °C on the hot stage of the microscope an unadulterated polypropylene sample is crystallized in the same way. Both samples are observed under a polarizing microscope during crystallization,the difference in spherulite size between nucleated and untreated polypropylene can be seen very clearly. An ordinary microscope can also be used by placing polarizers on the condenser and eyepiece, and adjusting these to give maximum darkness. 

G. Allegra, I. W. Bassi, C. Carlini, E. Chiellini, and G. Montagnoli Isomorphism Phenomena in isotactic poly-(4-methyl-substituted) a-olefins and in isotactic polyaikylvinyl ethers. Macromolecules (in press). 

Thin films of isotactic or elastomeric [51] polypropylene can be prepared from pellets by melt pressing. For this purpose several iPP or ePP pellets are placed between two sheets of thick aluminum foil and are subjected to pressure in in a hot press (T - 175°C pressure ca. 1-10 tons). Careful Wear appropriate safety shields and gloves After cooling the sample down to ambient temperature, the foil is unwrapped. If the polymer sticks to the foil, the film can be removed after cooling it down below the glass transition temperature e.g. in liquid nitrogen. Careful For... 

CM-AFM on Thin Films of Isotactic Polypropylene (iPP) a-iPP Melt-Pressing... 

Poly(methylmethacrylate)-g-poly(dimethylsil-oxane) (PMMA-g-PDMS) fractionation, 217-229 Polyoxyalkylene, 257-258 Polyphenol oxidase, 313 Polypropylene, 336 isotactic, 360-364 pressed sheet, 360-364 Polysilane polymers, 278 cyclohexyl-substituted, 277 Polysiloxane polymers, 278 fractionation, 217-250 functionally terminated, 273 Polysiloxane/PMMA copolymer fractionation, 217-250... 

Some measurements were made on an unoriented, commercially extruded, isotactic PPH film (25/xm, Enjay chill roll cast) and on an oriented commercial PPH monofilament [150/xm, Amtech Inc., Odenton, U.S.A., 90% residual elongation at break, stabilized with 0.24 wt % octa-decyl 3-(3, 5 -di-ter -butyl-4 -hydroxyphenyl)propionate]. The unprocessed PPH powder also was pressed into film ( 70 /on). All samples were Soxhlet-extracted with acetone (48 hr) and vacuum dried before use. The stabilizer in the commercial fiber was not removed by this treatment, although additives were extracted rapidly from low orientation samples (5). 

FIGURE 12.6 Plot of the glass transition temperature as a function of log r, where x is the number of chain atoms or bonds in the backbone. Data for (-0-) poly(a-methyl styrene), (-A-) poly(methyl methacrylate) (- -) polystyrene, (- -) poly(vinylchloride), (-A-) isotactic poly-propylene, (- -) atactic polypropylene, and (- -) poly(dimethylsiloxane). (From Cowie, J.M.G., Eur. Polym. J., 11, 297, 1975. With permission of Pergamon Press.)... 

Fig. 2.20 Examples of electron micrographs of polymers, (a) A defocussed bright-field image of a thin film of isotactic polystyrene annealed and crystallised at about 170 °C (b) An image of a fracture surface replica from a sample of linear polyethylene crystallised from the melt at 4.95 kbar. ((a) Adapted by permission of Masaki Tsuji and (b) adapted from Principles of Polymer Morphology by D. C. Bassett. Cambridge University Press 1981.)...

Fig. 4.2 Imagined planar zigzag conformations of vinyl polymers (a) the carbon backbone, (b) a regular isotactic configuration, (c) a regular syndiotactic configuration and (d) a random atactic configuration. The planar zigzag conformation might not be possible for the real chain because of steric hindrance. ( Cambridge University Press 1989.)...

Fig. 5.26 (a) The ideal response of T, as a function of T for a pair of protons 0.1 nm apart. The numbers in parentheses denote the values of o>a/ ln) in megahertz, (b) The T relaxation times for the ( ) methylene and (O) methine carbon atoms of isotactic propylene, ((a) Reproduced from Nuclear Magnetic Resonance in Solid Polymers by V. J. McBrierty and K. J. Packer. Cambridge University Press, 1993 (b) reproduced by permission of IBM Technical Journals.)... 

With respect to titanium catalysts for polymerization of ethylene or propylene, Ziegler synthesized the first high-density polyethylene and Natta prepared isotactic polypropylene by means of coordination catalysts about 50 years ago. The preparation methods of catalysts have been studied extensively. These TiCL3 catalysts have very high activity for homopolymerization of ethylene and propylene, whereas, they exhibit low activity for random copolymerization of ethylene with propylene when compared to vanadium catalysts. Refer to Ziegler-Nata Catalyst, Vanadium Catalysts, and EP Terpolymer, (Source Elastomer Technology Handbook, N. P. Cheremisinoff - editor, CRC Press, Boca Raton, Florida, 1993). 

Polypropylene (PP) has two crystalline forms. A monoclinic crystal (a-type) is obtained by slow crystallization from the molten state and a hexagonal crystal ( -type) is formed by annealing while a temperature gradient is maintained across the sample. Figure 5.25 A presents DSC heating curves of an isotactic PP film prepared by temperature gradient annealing [23]. The film was pressed at 473 K and cooled to 443 K, where the pressure was released. The... 

The data of paper [4] for nanocomposites based on industrial isotactic polypropylene (PP) of manufacture Shell Co. is used. As a filler natural clay Na -montmorillonite is used modified by four modificators, with volume contents cpy=0.025, 0.050 and 0.10. The more detailed description of nanocomposites in paper [4] is cited. Specimens for mechanical testing in the form of dog-bone with base lenght 10 mm and thichness 0.2 mm were produced by pressing from the melt at 473 K. The tension testing was made at temperatures 293 and 373 K... 

Al-Hussein M, Strobl G (2002) The melting line, the crystallization line and the equilibrium melting temperature of isotactic polystyrene. Macromol 35 1672-1676 Allen MP, Tildesley DJ (1989) Computer simulation of liquids. Oxford University Press, New York... 

Figure 3.1 The 25-MHz spectra of three preparations of polypropylene isotactic, atactic, and syndiotactic. (From Bovey, F.A., Chain Structure and Conformation (f Macromolecules, Academic Press, New York, 1982. With permission.)...

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