Isotropic polypropylene

X, = —1.3 X 10 K . The negative along the chain direction has been reported for a number of polymer crystals such as cotton cellulose [39], nylon 6 [39,40], isotropic polypropylene [41] poly(oxy methylene), [42] polychloroprene [39] and poly(ethylene terephthalate) [39]. The... 

Figure 1 Plot of I (q)vs for isotropic polypropylene crystallized in such a way that fragments of the chain are widely separated ( Tag = 179 000)...

Scattering from the drawn samples in the higher- region was greater than for identical undrawn samples and was nearer to that expected for an adjacent re-entry model (all isotropic polypropylene samples, regardless of their thermal histories, have approximately the same asymptotic scattering level). A tentative interpretation of this result is that the stems come closer together as the polymer is drawn. 

Figure 12.1 Photograph of necks formed in the drawing of (a) isotropic polypropylene and (b) oriented polyethylene.

For amorphous polymers, the increase in thermal conductivity in the direction of the draw is usually not higher than two. Figure 2.4 [24] presents the thermal conductivity in the directions parallel and perpendicular to the draw for high density polyethylene, polypropylene, and polymethyl methacrylate. A simple relation exists between the anisotropic and the isotropic thermal conductivity [39], This relation is written as... 

The dynamic mechanical behaviour of ultra high modulus polypropylene is shown in Fig. 32. As in LPE, the modulus is temperature dependent, rising to a value of 25 GPa at —140 °C, which is rather more than half (he value of 42 GPa obtained from crystal measurements. Although the a and y relaxations of the isotropic polymer can be seen in the highly drawn material, the -relaxation is undetectable. On annealing, the modulus at high temperatures is markedly reduced, and a P-relaxa-... 

The coil—rod—coil triblock molecule (17) based on polypropylene oxide) (PPO) coil segment was observed to show only an isotropic liquid upon melting. In contrast, the addition of greater than 0.10 mol of lithium salt/propylene oxide (PO) unit induces the formation of a liquid crystalline order (Figure 22). 

Fig. 3.3.5 H decoupled C spectra of isotactic polypropylene for different spinning frequencies o>r =l7tv and orientation angles i/r of the rotation axis, (a) Static sample. The wideline resonances of the different carbons overlap, (b) MAS spectrum with fast sample spinning. Narrow signals are observed at the isotropic chemical shifts only, (c) MAS spectrum with slow sample spinning. In addition to the centre line, sideband signals are observed at seperations naiR from centre lines, (d) OMAS spectrum with fast sample spinning. The orientation of the axis deviates from the magic angle. Each resonance forms a powder spectrum with reduced width, which can serve as a protractor (cf Fig. 3.1.3). Adapted from [Blu4] with permission from Wiley-VCH.

U.V. Makedonov, A.Z. Margolin, H.la. Rapoport, LS. Shibriaeva About the reasons of the change of effective constants of the rate of reactions of continuation and chains breaks in the period of oxidation induction of isotropic and oriented isotactic polypropylene////zg/zzzzo/eczz/z7r compounds (1986), 28 (A), No 7, 1380-1386 (in Russian). 

The extracorporeal shafts, 303 stainless steel and polypropylene, were prepared by dip coating the shafts into 1.0% (w/v) solutions of the copolymer and allowing the excess to drip off. The shafts were inverted and placed in a closed system to retard the rate of solvent evaporation. This technique resulted in an isotropic coating of the copolymer. 

An explanation was proposed for the PET results which has since been shown to apply equally to oriented polypropylene, high density polyethylene and nylon. The polymer sheet is considered as an oriented continuum characterised by three principal extension ratios Xi, X2, A3). If the isotropic sheet is considered as the state of zero strain, then the oriented polymer has extension ratios A3 in the draw or orientation direction (IDD) and it is convenient to take Ai in the direction of the sheet normal. Thus A3 and A2 define the projection of the strain ellipsoid in the plane of the sheet. When a deformation band forms in the oriented polymer the deformation can be described in terms of two shear... 

Makedonov Yu.V., Margolin A.L., Rapoport N.Ya. and al. (1986)." On the causes of changes in the effective rate constants continue and chain termination in the induction period of oxidation of isotropic and oriented isotactic polypropylene". Vysoconwlek. Soedin. V.28 A. No 7. PP.1380-1385. (In Russian)... 

Bokobza, L. Burr, A. Garnaud, G. Perrin, M. Pagnotta, S. (2004) Fibre Reinforcement of Elastomers Nanocomposites Based on Sepiolite and Poly(hydroxyethyl acrylate). Polym. Int. Vol.53, N0.8, pp.1060-1065, ISSN 0959-810 Bonduel, D. Mainil, M. Alexandre, M. Monteverde, F. Dubois, P. (2005) Supvported Coordination Polymerisation A Unique Way to Potent Polyolefin Carbon Nanotube Nanocomposites. Chem. Commun. Vol.l4, No.6, pp.781-783 Bruckner, S. Meille, S. Petraccone, V. Pirozzi, B. (1991) Polymorphism in Isotactic Polypropylene. Prog. Polym. Sci. 16, No.2-3, pp.361-404 Bryning, M. Islam, M Kikkawa, J. Yodh, A. (2005) Very Low Conductivity Threshold in Bulk Isotropic Single-Walled Carbon Nanotube-Epoxy Composites. Ado. Mater. Vol.17, N0.9, pp.1186-1191... 

That this form does indeed hold had been demonstrated for the cavitation of glassy polypropylene (Mott et al. 1993) in a computational study furnishing the validity of this extension of the universal binding-energy relation to symmetrical bulk response. The additional attraction of this expression is that it points out directly that application of a pressure produces symmetrical elastic compaction in an isotropic solid. However, more interestingly, one notes that, when dilatation is imposed, the bulk modulus monotonically decreases and eventually, at a dilatation of 1 /p, vanishes. This also leads to the observation that, if dilatation results from thermal expansion in response to a temperature increase, the bulk modulus also decreases. This simple observation represents the essence of the temperature dependence of all other elastic constants in anisotropic solids, beyond the mere effect on the bulk... 

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