Polyolefin melt properties

Macromolecules in solution, melt, or amorphous solid states do not have regular conformations, except for certain very rigid polymers described in Section 4.6 and certain polyolefin melts mentioned on page 139. The rate and ease of change of conformation in amorphous zones are important in determining solution and melt viscosities, mechanical properties, rates of crystallization, and the effect of temperature on mechanical properties. 

Vega, J. Aguilar, M. Peon, J. Pastor, D. Martinez-Salazar, J. Effect of long chain branching on linear-viscoelastic melt properties of polyolefins. E-Polymers 2002, 46, 1-35. 

The concept of recycling is most readily implemented if different structural components can be made out of the same material (Al, plastics), i.e., in one-material systems. Recently, polyolefins have appeared to fit the bill particularly well in this respect, i.e., the many potential forms of polyolefins have made possible adaptations for a wide variety of structural requirements. As an adjunct to these developments, polyolefin melt adhesives have been developed for bonding polyolefin parts to one another. Where this is feasible, total dismantling is no longer necessary and the parts can be reprocessed without any essential loss of properties. 

Bis(2,3-dibromopropyl ether) of tetrabromo-bisphenol A Polyolefins Melt-blendable for optimum physical properties... 

The effects of titanate coupling agents on the rheological properties of particulate filled polyolefin melts were studied by Han et al. [15]. Experi-... 

Knappe and Kress investigated the influence of repeated injection molding on the mechanical properties of samples for many different thermoplastics (Table 2.6) [32]. Similar experiments have also been performed by Shishova [33] and by Akutin and their co-workers [34] on polypropylene and polycarbonate, respectively, where decreases in tensile properties were found with repeated processing. Similar effects have also been reported during mixing of polyolefin melts in different equipment [30]. 

Structure on local nonrandom mixing effects whose many ramifications we wish to imderstand. While improving the predictive abilities of analytical theories, it is also desirable simultaneously to develop the numerically intensive off-lattice integral equation methods that are capable of describing the properties of polymer systems that contain structured monomers, of course, at the expense of heavy numerical computations. (See, for example, recent numerical studies of polyolefin melts using PRISM theory [33-35].)... 

Rohlfing, D. C., fanzen, L Melt-rheological characteristics of metaUocene-catalyzedpolyethylenes. in Metallocene-based polyolefins-preparation, properties and technology, Yo. 2 (1999) John WUey Sons, Ltd., Chichester pp. 419M34... 

Table 9 compares the most important properties of substrate materials based on BPA-PC, PMMA, and CPO (three different products) (216,217). The future will prove if the current disadvantages of CPO against BPA-PC regarding warp, processibiUty (melt viscosity), and especially cost can be alleviated. CycHc polyolefins (CPO) and, especially cycloolefin copolymers (COC) (218) and blends of cycloolefin copolymers with suitable engineering plastics have the potential to be interesting materials for substrate disks for optical data storage. 

Mechanical properties, such as elastic modulus and yield point, that depend on crystallinity per se are not seriously affected by low to moderate doses of ionizing radiation. On the other hand, those mechanical properties that are sensitive to interlamellar activity are most dramatically affected by the low to moderate radiation doses. This is seen in the ultimate tensile strength and elongation at failure of the polyolefins. It is also reflected in the large change in melt index between 0 and 18 Mrad, which indicates formation of cross-links that increase with increasing... 

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