Polymers compressibility

Consider the isothermal hydraulic system sketched below. A slightly compressible polymer liquid is pumped by a constant-speed, positive displacement pump so that... 

Compressed polymer matrices are widely used in sustained release. They are readily manufactured and make use of simple technology. However, they are among the most difficult to model and none can be relied on to produce true time-independent release. Despite these difficulties, many attempts have been made to improve and understand better the release kinetics. 

CM In Example 10.1, the local interparticle mechanical power dissipated into heat Wfed (watts) by FED during the passage of a compressed polymer particulates bed over the rotor wing-tip clearance region, is estimated by Eq. El0.1-2... 

In the case of a compressible polymer mixture, the RPA yields the same result but with the potentials matrix W replacing the excluded volumes matrix V ... 

Moreover the components of vector A change to become Aa = aA/vA, etc. An Ornstein-Zemike (OZ) approach (referred to as the integral equation theory) describing multicomponent compressible polymer blend mixtures has been extensively investigated [35]. The multicomponent OZ equation relates the direct correlations matrix C and the total (i.e., direct and indirect) correlations matrix H as ... 

Poly(vinylidene chloride) may be obtained from The Dow Chemical Co. as a white powder, designated saran A. To prepare saran charcoal from this powder it is first pressed into a convenient shape by use of a hydraulic press and steel die at a pressure of 15,000 p.s.i. The compressed polymer is then heated slowly in vacuo, starting at 125° C. and gradually increasing the temperature up to 750° C. The heating process takes about 3 weeks and the resulting piece of carbon retains the shape of the original polymer but is reduced in size in all directions by about 20%. 

Fig. 15. Normal and shear forces F between compressed polymer brushes sliding pass each other in a good solvent for a variety of systems. From Klein et al. [82].

FIGURE 17.3 Scaled repulsive force per unit area between two parallel plates covered with compressed polymer brush layers after they come into contact. P = P /NokT is the... 

It is also in this region that the elastic component becomes important because the compressed polymer melt expands as it leaves the die. This increase in diameter or thickness is related to the elastic deformation of the polymer at the die inlet. 

Guzatto R., Da Roza M. B., Denardin E. L. G., Samios D. (2009). Dynamical, morphological and mechanical properties of poly (ethylene terephthalate) deformed by plane strain compression. Polymer Testing, Vol. 28, pp. 24-29, ISSN 0142-9418 Karagiannidis P. G., Stergiou A. C., Karayannidis G. P. (2008). Study of crystallinity and thermomechanical analysis of annealed poly (ethylene terephthalate) films. European Polymer Journal, Vol. 44, pp. 1475-1486, ISSN 0014-3057 Keum J. K, Song H. H. (2005). Thermal deformations of oriented noncrystalline poly(ethylene terephthalate) fibers in the presence of mesophases structure. Polymer, 46, pp. 939-945, ISSN 0032-3861... 

A number of equation of state theories have been used to model phase behavior of polymers in supercritical fluids. For example the lattice-fluid theory of Sanchez and Lacombe[4U 42] includes holes on the lattice in order to model compressibility. The lattice-fluid theory has been applied to model phase behavior of both homopolymers and copolymers in supercritical fluids[32, 38, 43, 44]. The statistical associating fluid theory (SAFT)[43,45-48] and corresponding state models[49] have also been employed to model compressible polymer-solvent mixtures. Figure 1 gives the pressure-concentration phase diagram for poly(dimethyI siloxane) in CO2 modeled with the lattice-fluid equation of state[50]. 

M. Keskin and M. Gencarslan, Investigation of the phase behavior in a compressible polymer-solvent system using the full Tompa model... 

Can we expect this to be the case here To estimate the range of the reweighting factor, we briefly re-inspect the Hubbard-Stratonovich transformation of the total density + < b that leads to the fluctuating field 17. For simplicity we consider a one-component system. In a compressible polymer solution or blend, the contribution of the repulsive interaction energy to the partition function can be written as... 

Ruhl T, Spahn P, Hellmaim GP (2003) Artificial opals prepared by melt compression. Polymer 44 7625-7634... 

Lu H, Fu B, Daphalapurkar N, Hanan J, Soritrou-Leventis C, Leventis N (2008) Simulation of the evolution of the nanostructure of crossUnked sUica-aerogels under compression. Polymer Preprints 49 564—565. Bijsterbosch BH, Bos MTA, Dickinson E, van Opheusden JHJ, Walstra P (1996) Brownian dynamics simulation of particle gel formation From argon to yoghurt. Faraday Discuss 101 51-64. 

Generally for a compressible polymer blend the following requirement must be satisfied (5-7) ... 

M. Gottlieb and R. J. Gaylord, Experimental Tests of Entanglement Models of Rubber Elasticity 1. Uniaxial Tension Compression Polymer 1644-1646 (1982). 

Hydroxypropylmethylcellulose (HPMC) is a partially 0-methylated and partly 0-2-hydroxypropylaled eellulose ether, which is available in several grades with different DS and MS. It is widely used in the pharmaceutieal industry as a binder for the production of tablets, as a viscosity-modifying agent and as a component of film coatings on tablets. In particular the use of HPMC as a directly compressible polymer for the production of controlled release tablets has been widely reported (a. 11, a. 12). 

Spitzig, W.A. and Richmond, O. (1979) Effect of hydrostatic pressure on the deformation behaviour of polyethylene and polycarbonate in tension and in compression. Polymer Engineering and Science, 19 1129-39. 

C Vlattas, C Galiotis. Monitoring the behaviour of polymer fibres under axial compression. Polymer 32 1788-1793, 1991. 

C Vlattas, C Galiotis. Deformation behaviour of liquid crystal polymer fibres 1. Converting spectroscopic data into mechanical stress-strain curves in tension and compression. Polymer 35 2335-2347, 1994. 

The convex curve in the initial part of the extension (on the left edge of the curves) was due to the repulsive force exerted from the compressed polymer against... 

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