Polymer phase interphase

The interphase between the continuous and the discontinuous polymer phases differs with respect to blend preparations. Solution-cast blends produce inclusions that are pulled away from the matrix, whereas injection-molded blends show HPL striations that are closely associated with the matrix. 

The basic issue confronting the designer of polymer blend systems is how to guarantee good stress transfer between the components of the multicomponent system. Only in this way can the component s physical properties be efficiently used to give blends with the desired properties. One approach is to find blend systems that form miscible amorphous phases. In polyblends of this type, the various components have the thermodynamic potential for being mixed at the molecular level and the interactions between unlike components are quite strong. Since these systems form only one miscible amorphous phase, interphase stress transfer is not an issue and the physical properties of miscible blends approach and frequently exceed those expected for a random copolymer comprised of the same chemical constituents. 

In any attempt to understand the physico-chemical phenomena responsible for adhesion between a polymer phase, such as an adhesive or organic coating, and a solid substrate, there is a need to be able to access the interface or interphase... 

Particle morphology can be studied by fluorescence quenching if individual components of the particles can be labelled by covalent attachment of an appropriate dye [84]. The use of a fluorescence quencher to decrease the particle fluorescence intensity served to probe the interphase zone formation or the sharpness of the interface between polymer phases in the particles. 

Fiarticle morphology porosity, relative length scale of polymer and pore phases, particle shape, distribution of phases in high-impact polypropylene Interphase heat and mass transfer phenomena Intraphase heat and mass transfer phenomena Observed kinetics, rate limiting steps Phase equilibrium, monomer sorption and desorption in polymer phase, diffusion Fbrticle agglomeration Micromixi ng... 

It was reported that the compatibilizer normally gets adsorbed on the surface of the clay platelets and alters the interphase [92]. The tensile strength and tensile modulus are always good for CPN compared with PP. The nano-level dispersion of clay in PP plays a vital role in such an improvement. The stiffness of the silicate layers contributes to the presence of immobilized (or) partially immobilized polymer phases [93]. The orientation of the silicate layer and molecular orientation also play a vital role in the improvement of the stiffness. 

Most polymer blends are immiscible. Their flow is complex not only due to the presence of several phases having different rheological properties (as will be demonstrated later, even in blends of two polymers the interphase must be taken into account), but also due to strain sensitivity of blends morphology. Such a complexity might be best put in perspective by comparing the flow of blends with that of better understood systems, for example, suspensions, emulsions, and block copolymers. 

Mixtures of two or more polymers in polymer blends are another combination of different macromolecules. The different polymer components are normally incompatible and thus show phase separation, with the minor component usually in the form of the dispersed phase and the major component as the matrix. Close to the composition of 50 50, interpenetrating structures or networks are formed. This phase separation corresponds to the microphase separation in block copolymers but-owing to the absence of covalent bonds between the components-with coarser structures. Several processes are used to enhance the compatibility between the polymer phases, including grafting, mixing with compatibilizers, or reactive blending. Compatibilizers (block copolymers, graft polymers) cause a reduction in particle size of the minor component in the matrix. Between the components, separate interfaces (only thin boundaries) and interphases (thicker layers with often an own structure) exist. 

The permeant originally in phase 1 dissolves in the polymer interphase polymer/ phase 1. 

The monomer-saturated emulsifier layer (or the shell of polymer particlesX the high chain transfer constant to VC and the polymerization in the interphase should promote desorption of radicals from particles to the aqueous phase. Desorbed radicals may take part in initiation and termination or re-enter the particles. In both phases, desorbed or re-entered radicals are more eflicient in termination. In addition, the mobile radicals irreversibly diffuse to the particle core in which they are immobilized by the polymer phase and/or occluded by propagation. 

Most of the experimental evidence related to the interphase in the low ty nanocomposites was obtained at temperatures below the polymer reusing meso-scale test specimens. Assuming the chain immobilization to be the primary reinforcing mechanism on the nano-scale, spatial distribution of the conformation entropy within the polymer phase is of primary importance. Hence, experimental data for nano-composites above the matrix Tg has to be considered. Sternstein et aL [24,26,27] published an interpretation of the viscoelastic response of rubbery nanocomposite above the matrix Tg, i.e., the Payne effect. Kalfus and Jancar [144] analyzed the viscoelastic response of poly vinylacetate filled with uaiio-sized hydi oxyapatite over the temperature range from -40 to - -120°C and observed strain softening similar to the Payne effect [133,150]. 

At (co)polymerization of bifunctional monomer a solid polymer phase, which begins to form at very low conversion ( 1%), is a netwoiked polymer its solubility in a liquid monomer phase is small monomer solubility in networked polymer is also small, so copolymerization process in polymerie phase may be neglected. A new reaction zone - an interphase layer on the boundary liquid monomer phase (MP) -solid polymer phase (PP) - is formed. 

Thus, the proeess of polymerization of polyfimctional monomers is realized in two reaction zones in voliune of liquid monomer phase (MP), where dissolved polymer is absent practically, and in the interphase layer at the boimdary of MP and solid polymer phase (PP), where monomer solubility is small. Aeeording to this model of two reaction zones the kinetic equations were derived [18] ... 

Techniques based upon fluorescence and phosphorescence spectroscopy provide a wealth of information about morphology and dynamics in complex polymer syst s. These are systems typically ccmi osed of several different polymer phases separated by sharp interfaces or diffuse interphases. 

It should be noted once more that filled polymers may be treated as three-phase systems only nominally, since thermodynamically the interphase cannot be regarded as a phase in its own right. 

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