Polypropylene isotatic

As noted in the papers by Schaefer and coworkers and by Lyerla and coworkers, Tip data may be complicated by the fact that mechanisms other than spin-lattice interactions (namely spin-spin relaxation) are possible which don t map motional characteristics. In the case of polystyrene, Schaefer and coworkers conclude that the spin-spin contributions are negligible, whereas Lyerla and coworkers find that the levels of spin-spin and spin-lattice contributions for isotatic polypropylene and atatic polymethyl methacrylate were temperature dependent. 

J.E. Volponi, L.H.I. Mei, and D. dos Santos Rosa, The use of differential photocalorimetry to measure the oxidation induction time of isotatic polypropylene, Polym. Testing 2004, 23, 461 165. 

Figure 5.13 Solid-state CNMR spectra of polypropylene, (a) Solid-state CNMR spectrum of isotatic polypropylene (reproduced with modification from Fleming et al. [23] by permission of the American Chemical Society) plus representation of the helical conformation of isotactic polypropylene, (b) Solid-state NMR spectrum of syndiotactic polypropylene, plus represent-...

B De Roover, J Devaux, R Legras. Maleic anhydride homopolymerization during melt functionalization of isotatic polypropylene. J Polymer Sci Polymer Chem 34 1195-1202, 1996. 

Other polymers have other growth directions, e.g. monoclinic isotatic polypropylene grows faster along the a-axis. Similar behaviour is observed with... 

Stress-Relaxation Date for Slowly Quenched Isotatic Polypropylene... 

In the following subsections are given examples of the use of Raman spectroscopy to obtain this orientation information for three polymers isotatic polypropylene (iPP), high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET). 

What combination of metal compounds are catalytically effective for isotatic polypropylene synthesis ... 

Due to the industrial importance of the process, many semicrystalline polymers have been investigated polyethylene [116-121], isotatic polypropylene [122-127], polybutene-1 [128], polyoxymethylene (or poly acetal) [129-131], polyamide 6 [132], poly(phenylene sulphide) (PPS) [133], and so on. 

The most recent catalysts for syndiotactic polypropylene are complexes, like i-propyl(cyclopen-tadienyl-l-fluorenyl)hafiiium dichloride with methyl aluminoxane. Another, similar catalyst is /-propyl(/7 -cyclopentadienyl- / -fluorenyl)zirconium dichloride with methyl aluminoxane. These catalysts yield polymers that are high in syndiotactic material (the zirconium-based compound yields 86% of racemic pentads)Commercial production of syndiotactic polypropylene is in the planning stage. What catalytic system will be used, however, is not known at this time. Some of the properties of the two isomers, isotatic and syndiotactic polypropylenes, are compared in Table 5.5. 

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