Highly asymmetric polymer blends

COMPONENT DYNAMICS OF HIGHLY ASYMMETRIC POLYMER BLENDS... 

Interchain Coupled Chain Dynamics in Highly Asymmetric Polymer Blends... 

The Coupling Model is consistent with all the properties and has fundamental support from quasielastic neutron scattering and simulations. However, the emphasis of the entire section is on the many properties of component dynamics in HAPB that deserve attention and alternative explanation by researchers in glass transition and polymer chain dynamics and viscoelasticity. This is because the new physics found in the segmental and chain dynamics of components in highly asymmetric polymer blends could possibly revolutionize the current understanding of polymer dynamics and viscoelasticity. 

The most Important requirements of high selectivity and high permeability for the more permeable CO. gas seem to be met by the asymmetric CA blend membranes. They elnilblt the permeability rates of rubbery materials and the selectlvities of a glassy polymer with an Intermediate high glass transition temperature. 

Dhibar AK, Kim JK, Khatua BB. Co-continuous phase morphology of asymmetric compositions of polypropylene/high-density polyethylene blend by the addition of clay. J Appl Polym Sci 2011 119(5) 3080-92. 

One of the primary rationales for producing blends of polysulfone with other polymers is to use the polysulfone to impart separation and membrane capabilities to the material and for the second polymer to provide higher temperature performance than is possible with the use of the polysulfone alone. For example, in the next section of this chapter, blends of polysulfone with other high temperature polymers such as polyimides (Pis) and polybenzimidazole (PBl) will be discussed. Much of that effort is focused on the production of miscible blends that can be fabricated into both symmetric and asymmetric membranes. Later sections of this chapter will focus on the use of polysulfone in mixtures to modify other properties of polymers, particularly the fracture and impact behaviors. 

Another example of an alternative rubber system is the asymmetric radial polymer (ARPS). ARPS has four equal arms of polybutadiene, with a polystyrene segment attached to one of the polybutadiene arms. A HIPS product made with ARPS blends polybutadiene produces two separate rubber phases with different morphologies and particle size distributions. The ARPS produces a capsular morphology and the polybutadiene produces a normal cellular morphology surrounded by a lamellar structure that provides a reactor product with both high gloss and high impact. 

Further approaches to meet the requirement of high selectivity may Include the blending of glassy and rubbery polymers, the chemical alteration of the dense skin-layer of Integral-asymmetric membranes and morphological variations of dense polymer films by proper post-treatment—as exemplified In this paper for CA blend membranes. 

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