Amorphous phase viscosity

High crystallization rates and the possibility to stabilize X-ray amorphous phases, which exhibit ZSM-5 like properties, were among the reasons why we decided to investigate the procedure B in more detail. In order to optimize the particle size, homogeneity, morphology and composition, we have questioned more systematically the influence of secondary synthesis variables such as the pH, solvent viscosity or the nature of the alkali cation, added as chloride. 

Diffusion Rate Controlled Process If the rate of chemical reaction is much faster than the diffusion of water and EG through the solid amorphous phase, then the reaction can be considered to be at equilibrium throughout the pellet [21], The reaction rate is dependent upon the pellet size, the diffusivity of both water and EG, the starting molecular weight, and the equilibrium constants Ki and K5. In addition, the pellet can be expected to have a radial viscosity profile due to a by-product concentration profile through the pellet with the molecular weight increasing as the by-product concentrations decreases in the direction of the pellet surface [22-24],... 

For this reason one has to revise the deformation mechanism during microhardness determination commonly used for complex systems comprising components or phases with glass transition temperatures below room temperature. For this purpose it is convenient to remember again the structural peculiarity of the system under investigation. The fact that the PBT crystallites are floating in a matrix of low viscosity has important consequences on the microhardness behaviour. Because they are floating in a liquid of low viscosity, the crystallites of PBT as well as the PBT amorphous phase cannot respond to the external stress in a way that demonstrates their inherent microhardness, however, one can measure the response of the crystallites embedded in the liquid matrix. 

Summarizing, it can be concluded that a relatively sharp (within 2-4% of deformation) drop in H is observed for copolymers of PBT but in comparison with homo-PBT this transition occurs at much higher deformations (between 25 and 30%). This difference as well as the following increase and decrease of H are related to the structural peculiarities of thermoplastic elastomers - the presence of a soft amorphous phase which first deforms and the existence of a physical network. The very low H values obtained for PEE are related to the fact that the PBT crystallites are floating in an amorphous matrix characterized by a low viscosity. 

The tensile strength of a polymer containing an additional noncrystalline short-chain ester segment tends to reach a high value at relatively low inherent viscosity than one having only 4GT segments. Reduced volume swell in contact with nonpolar oils and fuels may also be attributed to the greater ester content of the amorphous phase. 

Secondly, the blend composition is of importance as well. The finer the dispersion (i.e., at low content of the amorphous phase, nearby equal melt-viscosities of matrix and dispersed phase. 

Many physical properties change in the vicinity of Tg (it is really a region), the most prominent being the dynamic ones. A transition between two dynamic states occurs in the amorphous phase—between the "glassy" state, wherein the mobility of chain fragments is frozen (frozen "free volume") and the elastic state wherein the chain mobility increases upon the rise of temperature (the free volume increases and viscosity decreases, respectively). (Free volume is defined as the difference between the volume of the liquid phase and the extrapolated value at absolute zero temperature.) It is customary to define the transition (TJ when a fraction of frozen free volume of 2.5% appears, and stays constant at lower temperatures. There is no "real" solidification, however, but a frozen liquid. The rate of the measurement (or the fre-... 

All three signals reflect the mobility of the PDMS chain At -160°C, the starting temperature of our DSC scans, PDMS consists of amorphous and crystalline domains. At temperatures above Tg, enhanced chain mobility in the amorphous phases leads to a change in Acp, provided there are more than 15 dimethylsiloxy (DMS) units in the PDMS chain, which is true for a free PDMS polymer with a viscosity of 1000 mPas (related to a chain length of about 200 DMS units). As samples are shock-frozen, there is always an excess of amorphous phase, which, with increasing mobility, crystallizes at -80°C At -35°C the system melts Affm-... 

There are numerous experiments on viscosity. Table 75 is taken from R. Schenck and the data indicate that the crystalline liquids can be considerably more viscous than the corresponding amorphous phases of the same chemical composition, but that the reverse is sometimes observed also. 

Indeed, one matter of concern in the development of new polymer ionic membranes lies in the fact that their high conductivity is often associated with amorphous, low-viscosity phases. Therefore, in their conductive form, these membranes behave like soft solids with poor mechanical stability their direct use in LPBs may give rise to those problems commonly met in conventional liquid electrolyte systems, such as leakage, loss of interfacial contacts and short circuits. Under these circumstances, one of the most useful feature of LPBs, namely the solid-state configuration, would then be lost. Consequently, it is of key importance to assure that the polymer electrolyte membrane maintains good mechanical properties even in its conductive state. 

---