Isotactic poly propylene

Figure 2 X-ray diffractograms recorded at room temperature, (a) Metallocene-synthesized isotactic poly(propylene), mmmm — 0.996 crystallized at 145°C. (b) Atactic poly(propylene). Reproduced with permission from Ref. [43], Copyright John Wiley Sons, Inc., 1999.

Table 1 Comparison of degree of crystallinity for metallocene isotactic poly(propylenes) from wide-angle X-ray scattering analyzed by different methods...

It has also been inferred that differences found between crystallinities measured by density and those from heat of fusion by DSC area determination, as given for polyethylenes in the example of Figure 4 [72], may be related to baseline uncertainties, or not accounting for the temperature correction of AHc. Given that similar differences in crystallinity from density and heat of fusion were reported for isotactic poly(propylene) [43] and polyfaryl ether ether ketone ketone), PEEKK [73], other features of phase structure that deviate from the two-phase model may be involved in the crystallinity discrepancy. 

Both vibrational spectroscopies are valuable tools in the characterization of crystalline polymers. The degree of crystallinity is calculated from the ratio of isolated vibrational modes, specific to the crystalline regions, and a mode whose intensity is not influenced by degree of crystallinity and serves as internal standard. A significant number of studies have used both types of spectroscopy for quantitative crystallinity determination in the polyethylenes [38,74-82] and other semi-crystalline polymers such as polyfethylene terephthalate) [83-85], isotactic poly(propylene) [86,87], polyfaryl ether ether ketone) [88], polyftetra-fluoroethylene) [89,90] and bisphenol A polycarbonate [91]. 

MHz, which determine the Tics, are the same for the non-crystalline region of isotactic poly(propylene) and for atactic poly(propylene). This in turn indicates that the disordered chain structure is the same for the two cases. 

Figure 11 Left Spherulites of a Ziegler-Natta isotactic poly(propylene) with Mw = 271,500 g/mol and mmmm — 0.95, isothermally crystallized at 148°C. Right Banded spherulites of a linear polyethylene with Mw = 53,600 g/mol slowly cooled from the melt.

Figure 17 Isothermal melting of Ziegler-Natta isotactic poly(propylene). (a) Spherulites with mixed birefringence at Tc = 148°C. The top middle figure displays the melting for the same thermal history, (b) Subsequent to crystallization, the temperature was raised to 171°C spherulites acquire negative birefringence, (c), (d) and (e) Isothermal melting at 171°C for 80, 200 and 300 min, respectively. Reproduced with permission from W.T. Huang, Dissertation, Florida State University, 2005. (See Color Plate Section at the end of this book.)...

Here m is the mode order (m — 1,3,5. .., usually 1 for polyethylenes), c the velocity of light, p the density of the vibrating sequence (density of pure crystal) and E the Young s modulus in the chain direction. The LAM band has been observed in many polymers and has been widely used in structural studies of polyethylenes [94—99,266], as well as other semi-crystalline polymers, such as poly (ethylene oxide) [267], poly(methylene oxide) [268,269] and isotactic poly(propylene) [270,271], The distribution of crystalline thickness can be obtained from the width of the LAM mode, corrected by temperature and frequency factors [272,273] as ... 

Table 8. Isotactic poly(propylene) polymerized by bridged- and unbridged-metallocene catalysts... 

Optical compensation for polymers with chiral monomeric units may also occur when the racemic polymer consists of crystallites, each composed only of the rectus chains or only of the sinister polymer chains, and a same amount of optical antipode crystallites is present. This intercrystallite optical compensation211 has been found, for instance, in isotactic poly(propylene sulfide),212 poly ((3 -methy lpropiol ac (one),213 and poly(isopropylethylene oxide),214 where isochiral 2/1 helical chains are included in orthorhombic unit cells according to the space group P2 2 2. ... 

Similarly the term isotactic was applied by Price and Osgan (78) to the crystalline polymer obtained from optically active and racemic propylene oxide. The zigzag and Fischer representations of an isotactic poly(propylene oxide) are shown in 36 and 37 (Scheme 7). Their different appearance is due, as already explained in a similar case, to the odd number of chain bonds existing in each monomer unit. Formula 36 presents alternately substituents on both sides of the chain and is very similar to the actual structure observed in the crystal state (79). 

We had studied mainly the propylene oxide polymerization, because the requirement for stereoregulation imposed on the catalyst was supposed to be severest for this monomer among alkylene oxides. The catalysts extensively studied are R2A10A1R2 and EtZnNBu ZnEt, which are composed of two metal atoms (59). The latter catalyst, being a crystalline compound, is characterized by giving an isotactic poly-propylen oxide in high yield. 

From the viewpoint of polymer applications, the full exploitation of the combined resolution/sensitivity enhancement techniques to obtain "high-resolution" spectra of rare-spin nuclei in solids requires variable temperature spinning capability. In this paper, we describe briefly a spinner assembly suitable for routine operation over a wide range of temperature at the full complement of spinning angles and report - C spectral data at low temperature on several polymers, including fluoropolymers. In addition, variable temperature spin-lattice and rotating frame relaxation times are reported for isotactic poly(propylene). 

Figure 28 Stereoerror pentads expected for essentially isotactic poly propylenes, generated under catalytic-site control (top) and under chain-end control (bottom).

In this paper, we report the first extensive sub-ambient VT-MAS 13C T j and Tj data on macromolecules. The emphasis of the study was placed on isotactic poly(propylene)(PP) and atactic poly(methylmethacrylate)(PMMA) as they represent semi-crystalline and glassy polymers, respectively. Specifics of the investigation were directed to the issue of elucidating sidechain and backbone motions from the high frequency relaxation experiments. 

Figure 2. The 13C spin-lattice relaxation times at 15 MHz for isotactic poly (propylene) methylene ( ), methine (O), and methyl (A) carbons.

FEL 06] Feller J.F., Roth S., Bourmaud A., Conductive polymer composites electrical, thermal, and rheological study of injected isotactic poly(propylene)/long stainless-steel fibers for electromagnetic interferences shielding . Journal of Applied Polymer Science, vol. 100, pp. 3280-3287,2006. 

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.)... 

With poly(tetrafluoroethylene), on the other hand, the distance between fluorine atoms bonded to adjacent carbon atoms in the T conformation is 0.25 nm, which is smaller than the sum, 0.28 nm, of the van der Waals radii. Thus, the main chain atoms deviate from the ideal T conformation by means of a small change of from 0° to 16° in the torsion angle (see also Figure 4-7). The deviation of carbon chains from the T conformation increases with size of the substituents. For example, with isotactic poly(propylene), having the monomeric unit -(-CH2—CH(CH3), every second conformation in the lowest energy state is a G conformation, such that the whole chain adopts the. . . TGTGTG. . . conformation. This sequence of microconformations leads to a helix macroconformation. 

Two chains of the same chirality and conformation are isomorphous with respect to each other. Thus, two isotactic poly(propylene) helices, each with the same conformational sequence. . . TG TG TG. . . are isomorphous. Two such chains are also isoclinal if the bond vectors in each chain always have the same positive or negative orientation. With anticlinal chains, however, the bond vectors of one chain have the reverse orientation to those of the other chain (Figure 5-11). Thus, although the chains of the polyamides 6 and 6,6 are parallel to each other, the former is anticlinal and the latter is isoclinal (Figure 5-10). 

It is not only the crystallization rate, however, which is influenced by nucleating agents, but also the morphology. Isotactic poly(propylene) crystallizes monoclinically in the presence of / -/-butyl benzoic acid and pseudohexagonally when the quinacridone dyestuff. Permanent Red EBB, is added. 

The poly (olefin) fibers are manufactured in the largest volumes thanks to the low cost of the polymers and the simple melt-spinning production technology. Annual worldwide production of textile products based on poly(olefins) was 1.7 10 t/a in 1985, 90 % of which was isotactic poly(propylene) PP and 10 % high-density poly(ethylene) HOPE [81]. ... 

Stocker, W. et al. (1998). Epitaxial Crystallization and AFM Investigation of a Frustrated Polymer Structure Isotactic Poly(propylene), p Phase. Macromolecules, Vol.31, Issue 3, pp. 807-814. 

The characteristics of the samples used are summarized in Table 1 where SBR, PB and PI designate, respectively, a random copolymer of poly(styrene-random-butadiene), polybutadiene, and polyisoprene. Binary mixtures of PP/EPR (14), X-7G/PET (15), both having (50/50 wt/wt composition), and PS/SB (16) (35/65 w wt) were occasionally us, where PP, EPR, X-7G, PET, PS and SB, designate, respectively, isotactic poly(propylene), a random copolymer of... 

Multiple melting peaks are observed when the polymer exhibits polymorphism like nylon 6, 6 and isotactic poly(propylene) (/-PP). 

Poly(ethylene oxide) decomposes upon heating at lower temperatures than does polyethylene. Among the volatile products are found formaldehyde, ethanol, ethylene oxide, carbon dioxide, and water. Polyipropylene oxide) is also less heat stable than polypropylene. Isotactic poly(propylene oxide) is somewhat more stable than the atactic one. 

He, A. H., Hu, H., Huang, Y, Dong, J.-Y, and Han, C. C. 2004. Isotactic poly (propylene)/ monoalkylimidazolium-modified montmorillonite nanocomposites Preparation by inter-calative polymerization and thermal stability study. 

Stereoregular polymers of infinite molecular weight, dissymmetric main-chain atoms, and dissymmetric substituents show no optical activity resulting from the configuration, because of intramolecular compensation. Thus, isotactic poly(propylene) is not optically active. Stereoregular polymers with asymmetric main-chain atoms, such as - NH—CH(CH3)— poly(L-alanine), and -[-O—CH(CH3)—poly(L-propylene oxide), are optically active because of the configuration itself. 

Propylene, CH2=CHCH3, is obtained as a by-product of ethylene production from the cracking of petroleum fractions. Free radical polymerization yields only low-molecular-weight oils consisting of branched, atactic molecules. Isotactic poly (propylenes) were first made possible and came into commercial use through Natta s work with Ziegler catalysts. 

The spectra of stereoregular polymers show a single sharp line for each chemically distinct carbon because within each type of chain, each monomer residue is identical. However, the chemical shifts for isotactic and syndiotactic chains are not the same. For example, in isotactic poly(propylene), the CH3, CH and CH2 carbons occur at 20.0, 27.1 and 44.4 ppm, respectively, whereas in syndiotactic poly (propylene), the corresponding shifts are 18.7, 27.0 and 45.4 ppm [53]. NMR does not yield an unequivocal identification of the tacticity as does the CH2 proton spectrum, but it does permit different tacticities to be distinguished. 

Polyolefine blends are group of versatile materials, which properties can be tailored to specific applications already at the stage of compounding and further processing. Our previous papers on elastomer/plastomer blends were devoted to phenomenon of co crystallization in isotactic poly-propylene/ethylene-propylene-diene rubber (iPP/EPDM) [1] or surface segregation in low-density polyethylene/ethylene-propylene-diene rubber (LDPE/EPDM) [2, 3] systems. Composition and structure of the materials were related to their properties. Recently, we have described the influence... 

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