Polyolefins systems

In white reductions, P.R.208/polyolefin systems only withstand temperatures below 200°C, while transparent specimens (0.1%) are stable up to approximately 240°C. Thus the pigment is a suitable and economical candidate for polypropylene spin dyeing, provided the temperature is kept below 200°C. It is also possible to apply higher temperatures if a color shift towards more yellowish shades is acceptable. In terms of lightfastness, P.R.208 meets the common standards for interior application. 

Transparent and reduced 1/3 SD polyolefin systems are stable up to 300 to 320°C. 0.25% pigment is required in order to formulate 1/3 SD HDPE samples containing 1% TiOz. P.O.43, incorporated in injection-molded partially crystalline plastics such as HDPE, affects the shrinkage of the medium, which precludes its use in nonrotation symmetrical injection-molded articles (Sec. 1.6.4.3). 

Transparent polyolefin systems containing P.R.88 are stable up to 260 to 300°C, depending on the type and on the pigment content. 1/3 SD systems are heat stable up to approximately 240 to 260°C. Some types are recommended only for use in LDPE at low processing temperatures. The lightfastness of such specimens is between step 6 and step 7 on the Blue Scale. P.R.88 considerably affects the shrinkage of injection-molded articles, a feature which somewhat restricts its application in such systems. 

In terms of heat stability, 1/3 SD polyolefin systems containing P.V.23 withstand exposure to 280°C. In lighter tints, this value is appreciably lower 1/25 SD... 

Marosi, G., Bertalan, G., Rusznak, I., and Anna, P. 1986. Role of interfacial layers in the properties of particle-filled polyolefin systems. Colloids and Surfaces 23 185-98. 

Marosi, G., Anna, P., Bertalan, G., Szabo, S., Ravadits, I., and Papp, J. 2001. Role of interface modification in flame retarded multiphase polyolefin systems. In Fire and Polymers Materials and Solutions for Hazard Prevention, Vol. 797. eds. Nelson, G. and Wilkie, C. Washington, DC American Chemical Society, pp. 161-71. 

Marosi, G., Anna, P., Marton, A., Bertalan, G., Bota, A., Toth, A., Mohai, M., and Racz, I. 2002. Flame-retarded polyolefin systems of controlled interphase. Polymers for Advanced Technologies 13 1103-11. 

Santamaria and White (24) studied melt flow behavior and splnnablllty of several polyolefin systems including HDPE/LDPE blends. Defining the steady state compliance as ... 

Acetylenes are not the only compounds with organic tt systems which can substitute in metal carbonyls, and the same general synthetic methods can be used for other ligands. Reaction of carbonyl clusters with polyolefin systems, such as 1,5-cycloocatadiene and 1,3,5,7-cyclo-octatetraene, have produced substituted carbonyl systems, but only with Ru3(CO)i2 have clusters been isolated. Arene-substituted carbonyl clusters have also been obtained, as has been described in Section II.D.l. 

Interfacial effects on multiphase polymer systems have been of interest to polymer scientists. Apphcation of this strategy to commercially important polyolefin multiphase systems to produce tuned and/or stabilized morphologies is certainly attractive. Recently, polyolefin block copolymers have been introduced commercially and may be effective in controlling the morphology of related multiphase polyolefin systems, such as hiPP and TPO. 

To be of maximum synthetic value, the generation of the cationic site that initiates cyclization should involve mild reaction conditions. The most versatile systems to date have been allylic alcohols, which are readily cyclized in acidic media. Formic acid and Lewis acids such as stannic chloride have proved to be effective reagents for cyclizing polyolefinic allylic alcohols. Acetals generate a-alkoxy car-bonium ions in acidic solutions and can initiate the cyclization of appropriate polyolefinic systems ... 

In this chapter, the possibihty of using late transition metal catalysts to synthesize polyolefins in supercritical carbon dioxide was demonstrated [43]. The multicomponent phase behavior of polyolefin systems at supercritical conditions was studied experimentally by measuring cloud-point curves as well as by modeling polymer systems at supercritical conditions. The cloud-point measurements show that CO2 acts as a strong antisolvent for the ethylene-PEP system, which implies that the polymerization concerned will involve a precipitation reaction. The model calculations prove that SAFT is able to describe the ethylene-PEP-CO2 system accurately. Solubility measurements of the Brookhart catalyst reveal that the maximum catalyst solubility is rather low (in the order of 1x10 mol L ). However, a number of strategies are given to enhance this value. 

Broadband dielectric spectroscopy is a powerful tool to investigate polymeric systems (see [38]) including polymer-based nanocomposites with different nanofillers like silica [39], polyhedral oligomeric silsesquioxane (POSS) [40-42], and layered silica systems [43-47] just to mention a few. Recently, this method was applied to study the behavior of nanocomposites based on polyethylene and Al-Mg LDH (AlMg-LDH) [48]. The properties of nanocomposites are related to the small size of the filler and its dispersion on the nanometer scale. Besides this, the interfacial area between the nanoparticles and the matrix is crucial for the properties of nanocomposites. Because of the high surface-to-volume ratio of the nanoparticles, the volume fraction of the interfacial area is high. For polyolefin systems, this interfacial area might be accessible by dielectric spectroscopy because polyolefins are nonpolar and, therefore, the polymeric matrix is dielectrically invisible [48]. 

As suggested in the introduction the development of TREF was in response to the need to know something more about polyolefins, in addition to their molecular weight distributions, which might relate to those properties dependent on crystallinity. The hope and expectation is that through crystallizability separation it will prove possible to provide a more complete picture and understanding of the relationship between synthesis conditions and structure and between structure and properties for semicrystalline polyolefins. The way in which TREF has been used in the evaluation of the various polyolefin systems is reviewed in this section. 

Compounders in the US, such as UVTEC Inc., have brought out metal hydrate concentrates under the name Safe FR. These concentrates are loaded with in excess of 70% magnesium hydroxide and find uses in polyolefin systems for wire and cable, building products market and in the E E sector. 

RE Lee, 01 Kuvshinnikova, JM Zenner. Interactions of Pigments and Hindered Amine Light Stabilizers in Polyolefin Systems. Hilton Head, SC, March 2-4, 1998. 

Benzophenones are good general-purpose UV absorbers for clear polyolefin systems, and can also be used in pigmented compounds. Benzotriazoles are used mainly in polystyrene. Both can also be used in polyesters. Concentrations are usually about 0.2 5-1.0%. 

The other polycondensate/polyolefin system, the PE/PET blend, is morphologically quite similar to PP/PET. However, the orientational state of PE after melting by compression molding is different since PE crystallizes in a completely isotropic state [45]. Concerning the mechanical properties of the PE/PET system, it is noteworthy that after cold drawing, an increase in the mechanical properties by a factor of 6 for a and 3 for E can be achieved. Interestingly, these values are preserved after isotropization at 215 °C when the drawn blend is converted into a pol5rmer-polymer composite of the MFC type. 

The Sako-Wu-Prausnitz equation of state was also applied to high-pressure phase equilibria of polyolefin systems by Tork et alP The calculations were based on the pseudo-component method where the number of pseudo-components used were between 2 and 8. The small number of pseudo-components is a result of the very efficient estimation method used to adjust the pseudo-components to the moments of the distribution function (described in section 9.3.1). In so doing Tork et alP were able to provide a good description of the experimental data and show, perhaps not surprisingly, the agreement between calculated and experimental data improved with increasing number of pseudo-components. 

Typical end use applications include textiles and fibers, particularly as an anti-yellowing agent for elastomeric nylons (i.e., spandex or lycra). In addition, it can be used in polyolefin systems where fading or phenolic yellowing is known to occur. 

The selected mechanical properties refer to one-component polyolefin systems. 

EPR random copolymers, and EPDM diene terpoly-mers for higher reactivity, have been widely used in polymer blends. Their use as the major ingredient, and as additives to nonpolyolefins, will be discussed here. Their use as additives in other polyolefin systems can be found throughout this entire survey. 

A similar insensitivity of Tc to M has been observed [60] for binary blends of poly(isobutylene) (PIB) with several other polyolefins, systems for which it is difficult to imagine that any specific interactions could be responsible for the observed dramatic departures from the predictions of FH theory. (Note... 

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