Polyolefin Solutions

Table 8. Mark-Houwink Parameters for Polyolefin Solutions ...

Charlet, G. Ducasse, R. Delmas, G., "Thermodynamic Properties of Polyolefin Solutions at High Temperature 2. Lower Critical Solubility Temperatures for Polybutene-1, Polypen-tene-1 and Poly(4-methylpentene-1) in Hydrocarbon Solvents and Determination of the Polymer-Solvent Interaction Parameter," Polymer, 22, 1190 (1981). 

Uberall, M. Kapfer, K. Brauer, F. Trippler, R. Devolitalization operations for high volume polyolefin solutions. In Polyolefins IX, Conference Proceedings, Houston, TX, February 26-March 1, 1995 323-338. 

Solution intercalation—To prepare polymer nanocomposites, typically the organically modified LDH is dispersed in a solution containing polyolefin. The resultant dispersion is then stirred or aged under nitrogen atmosphere to accomplish the polyolefin intercalation. For example, Qu et al. [19,20] prepared and characterized polyethylene/ LDH by this method using dodecylsulfate (DS)-modified LDH (LDH-DS). The nanocomposites were obtained by refluxing the mixture of LDH-DS and fhe polyolefin solution in xylene. 

Additional references on preparation of polyolefin solutions should be noted [12, 13]. Most workers now favor a strategy of heating initially at a higher temperature (160 170°C) for a shorter time (1-2 h), followed by additional heating at about 140°C until dissolution is obtained. 

FIG. 3 A viscometer suitable to use at elevated temperatures with polyolefin solutions. Dissolution, filtration, and measurements can all be conducted under an inert atmosphere. Solvent and polymer are introduced through tube 1. The viscometer is then fiushed with nitrogen and evacuated through stopcock 2. The viscometer and its contents may then be heated to the desired temperature while the pol5uner dissolves. Filtration and measurements are conducted by manipulating stopcocks 3, 4, and 5. (Reproduced with permission from Ref. 69. Copyright 1966, John Wiley Sons, Inc.)... 

Polymer solutions and blends play an important role in polymer science and technology and the basic foundations of their properties, such as thermodynamics and rheology, require fundamental as well as applied studies. In this chapter we concentrate on the thermodynamic properties of polyolefin solutions which are important for understanding the state of systems used in bulk or solution polymerization, and also for the design of fraetionation proeedures with the objective to prepare fractions large enough to allow the study of their properties. 

In bulk and solution polymerization it is an advantage for process designers to have a knowledge of the phase separations that may occur during production. Such phenomena are mostly undesired and the best way to find methods to avoid them rests in a thorough study of the thermodynamic properties of the system in hand. This chapter provides the tools for such an approach. It is demonstrated that molecular models exist, capable of supplying a nearly quantitative description of available data on partial miscibility of polyolefin solutions. Such models cannot by themselves predict phase behavior some measured data will have to be fitted to the model for a given system, after which much experimental time can be... 

In Pennings procedure a mildly stirred polyolefin solution is cooled slowly. In the first stages of the process the longest chains deposit in the form of long fibrous crystals which build up a tenuous fabric-like... 

So far, the only polyolefin solutions treated with the SS theory refer to the system n-hexane/PE, for a wide range of molar masses and involving the assumption that the PE samples were molecularly monodisperse [64]. It was shown that LCM binodals and spinodals at various pressures can be represented by master curves over a reasonable temperature distance from the critical point (Fig. 10). It was furthermore demonstrated that the prediction of LCM phase behavior in... 

In the last decade attempts have been made to develop improved models, capable of providing quantitative predictions of thermodynamic properties of polymeric systems. We are not aware of any application so far to polyolefin solutions and therefore merely mention some relevant references [72-74], concentrating in this chapter on the older and still useful approaches. 

Although no simple model exists, capable of ad hoc prediction of thermodynamic properties of polyolefin solutions in undocumented cases, the treatments discussed here do supply a manageable mathematical framework that greatly reduces the need for extensive experimentation. 

The use temperature of a polyolefin elastomer is determined by the range between the Tg and the Tm. These new OBCs have increased the use temperature range of olefin-based elastomers by > 40 ° C, enabling the introduction of these polymers to many new markets and applications where a polyolefin solution was previously unavailable. The extension of the tem-peramre plateau and network structure that is developed from the OBC s crystallinity translates to better high-temperature elastomeric properties for the OBCs. For example, the 70 °C... 

CHA Charlet, G. and Delmas, G., Thermodynantic properties of polyolefine solutions at high temperature,/ o/ymer, 22, 1181, 1981. 

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