Homogenous polymer-blend composite

A polymer blend is created when two miscible polymers are mixed together. As in the case of composites, the impetus for creating polymer blends is to combine attributes of the two polymers to create a new material with improved performance. In practice, this is difficult with polymer-polymer solutions, since most common polymers do not mix well with one another to form homogeneous, one-phase solutions. 

Window autoclaves have been built to allow one to determine visually the appearance of turbidity in a homogeneous polymer solution, indicating the onset of phase separation, and to observe the resulting number of liquid and gaseous phases and optionally to determine their composition. Lentz [40] developed a mechanically driven stirrer fitted in a 2000-bar window autoclave. This apparatus allowed fast homogenation of concentrated polymer solutions and blends having low viscosity. 

Blending of polymers is an attractive method of producing new materials with better properties. Blends of aliphatic polyesters, especially of poly(e-CL), have been investigated extensively and have been the subject of a recent review paper [170]. Poly(e-CL) has been reported to be miscible with several polymers such as PVC, chlorinated polyethylene, SAN, bisphenol A polycarbonate, random copolymers of Vdc and VC, Vdc and AN, and Vdc/VAc, etc. A single composition-dependent Tg was obtained in the blends of each of these polymers with poly(e-CL). This is of interest as a polymeric plasticizer in these polymers. Blends of PVC and poly(e-CL) with less than 50 wt % of poly(e-CL) were homogeneous and exhibited a single Tg. These blends were soft and pliable because the inherent crystallinity of poly(e-CL) was destroyed and PVC was plasticized... 

In the case of vinyl chloride polymerisation in polyfbutyl acrylate) these materials are completely miscible but a two phase region exists within the phase diagram as shown in Fig. 4 Polymerisation from A to B produces a homogeneous blend whereas from E to F produces a two phase structure. Composition B can be reswollen to C with vinyl chloride which can then be polymerised to D to producea homogeneous blend. This route avoids the two phase region in the phase diagram and in principle all compositions of polymer blend can be prepared in a series of steps. 

Since this critical interaction parameter is very small for blends of long chains, most polymer blends have x > Xc and thus are phase separated over some composition range (within the miscibility gap). Only blends with either very weak repulsion (0 < x < Xc), or a net attraction between components of the mixture (x < 0) form homogeneous (single-phase) blends over the whole composition range. 

Among Its many attributes, poly(e-caprolactone) (PCL) Is particularly unique In Its capability to blend with different commercial polymers over a wide composition range. Incorporating FCL segment with other rubbery or glassy blocks will allow us to form novel multiphase block polymers. Such specialty polymers are often used as "oll-ln-oll" type of emulsifiers In polymer blends, whose mechanical properties can be Improved If better homogeneity Is achieved by the emulsifier additives (, ) ... 

Earlier work done in these laboratories has shown that polymer blends wherein the barrier polymers are dispersed as thin platelets parallel to the surface of the fabricated article, have significantly improved permeability barrier properties than the conventional "homogeneous", uniform, dispersions (1,2). The high barriers demonstrated were then achieved by blending 15-20% polyamides with a linear polyethylene, which achieved performance comparable to that obtained by adding as much as 50% nylon by conventional blending. While this performance has been satisfactory for a variety of applications, some of the more demanding uses require that the barrier polymer be used more efficiently. Described here are such blend compositions which show substantial resistance to permeation of hydrocarbon solvents and their mixtures. 

The PPE/PS mixtures are considered classical examples of miscible polymer blends. Within the accessible range of temperatures, single phase melts have been observed with the size of homogeneity below 20 nm. Dynamic flow behavior of PPE/PS blends, with the molecular weight ratio MW(PS)/MW(PPE) = 1, was studied in a wide range of temperatures and compositions [Prest and Porter, 1972]. The authors assumed additivity... 

The scanning electron microscopy (SEM) revealed that both ternary and binary blends have a phase morphology typical of blend composites with active interphase interaction between polymer components. At equal concentrations of g-PO in blends, the ternary systems look more homogeneous than binary ones. It may be presumed. 

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