Solubility parameters glassy polymers

The outstanding morphological feature of these rubbers arises from the natural tendency of two polymer species to separate one from another, even when they have similar solubility parameters. In this case, however, this is restrained because the blocks are covalently linked to each other. In a typical commercial triblock the styrene content is about 30% of the total, giving relative block sizes of 14 72 14. At this level the styrene end blocks tend to congregate into spherical or rod-like glassy domains embedded in an amorphous rubbery matrix. These domains have diameters of about 30 nm. 

Figure 3. Correlation between the solubility parameter of several glassy polymers and the Ideal separation factors for the CO2/CH. system calculated using the pure component permeabilities at 35 for a 20 atm upstream pressure of each component.

Table I Mobility and solubility contributions to the permeability and selectivity of typical glassy polymers at 35°C for a 20 atm pressure of both components based on pure component parameters.

In Figure 2.7, we report the case of two glassy polymer blends the solubility of CH4 in PS-TMPC (tetramethyl polycarbonate) blends of different compositions (0-20-40-60-100% of PS) is shown in Figure 2.7a at 35° while the solubility isotherms of COj in five different blends of (bisphenol-chloral) polycarbonate (BCPC) and PMMA (0-25-50-75% of PMMA)[" 1 at 35° C are shown in Figure 2.7b. The NELF estimation of the solubility is also reported, based only on the pure component characteristic parameters... 

Attempts have been made to rationalise the susceptibility of glassy polymers to ESC. The critical strain for crazing is a minimum when the solubility parameter 8 of the liquid is the same as that of the polymer (Fig. 10.19). The former is calculated from the energy of vaporisation and molar volume V of the solvent... 

The FFV value in the polymer phase of the mixed matrix can be calculated through Equation (7.11) based on the unpenetrated polymer density pi in the polymer phase of the MMM, obtained from the solubility data as indicated above. Since different filler loadings will induce different FFV in the polymer phase, one can use Equation (7.16) to obtain the parameters A and B virtually from as little as two different mixed matrices with two different filler loadings then the same Equation (7.16) can be applied to calculate or correlate the infinite dilution apparent diffusivity Dim for any other filler loading in the same glassy polymer. 

A plasticiser is a material incorporated in a plastic to increase its workability and flexibility or distensibility. The melt viscosity, elastic modulus and Tg of a plastic are lowered by a plasticiser addition. There are several theories to explain plasticiser effects such as the lubricity, gel, and free volume. Plasticisers are essentially nonvolatile solvents and therefore, polymer and plasticiser compatibility is very important and the solubility parameter difference (A8) should be less than 1.8. When present in small amounts plasticisers generally act as antiplasticisers, (i.e., they increase the hardness and decrease the elongation of polymers). Figure 6.12 illustrates the effect of plasticiser on modulus. Increasing concentration of the plasticiser shifts the transition from the high modulus (glassy) plateau region to the low, i.e., to occur at lower temperature [9]. 

Two separate cases must therefore be considered, ideal systems where both the di sivity and the solubility are constant, and concentradon dependent systems where the solubility and the diffusivity are functions of the concentradon.(Other cases can be distinguished where the solubility and the difiusivity are funedons of other parameters, such as dmeand place. These phenomena, oftm termed anomalous", can be observed in glassy polymers where relaxadon phenomena occur or in heterogeneous types of membranes. These cases will not be considered fiirtha here.)... 

Thus the length of the cyclized segnents bears both On the mechanism of the cyclization and, presumably, on the properties of the cyclized material. Properties such as the softening point and the solubility parameter are particularly im rtant in the context of block copolymer thermoplastic elastcxn s diich the hard or glassy bloc are cycliz polyiscjprene. " It is the advent of such blocik c polymers vhich provid the impetus for further stucfy of cyclized polyisoprene itself on our part. 

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