Glassy-rubbery transition

Drug release from swellable matrix tablets is based on the glassy-rubbery transition of the polymer which occurs as a result of water penetration into the matrix. Therefore, the gel layer is physically delimited by the erosion (swollen matrix-solvent boundary) and swelling (glassy-rubbery polymer boundary) fronts. 

Here, u is the solvent volume fraction at which the glassy-rubbery transition occurred and L is the half-thickness of the polymer slab. 

Synthetic binder 5 (Figure 10.3) has a similar behaviour to synthetic binders 3 and 4 as it has an intermediate composition. Once more, the same regions are observed in the mechanical spectrum of the hlend glassy, rubbery and terminal. In addition, as in the rest of the binders, the presence of a crossover frequency in the glassy-rubbery transition region between 0 and 25 °C is shown. 

Stress relaxation master curve. For the poly-a-methylstyrene stress relaxation data in Fig. 1.33 [8], create a master creep curve at Tg (204°C). Identify the glassy, rubbery, viscous and viscoelastic regions of the master curve. Identify each region with a spring-dashpot diagram. Develop a plot of the shift factor, log (ax) versus T, used to create your master curve log (ot) is the horizontal distance that the curve at temperature T was slid to coincide with the master curve. What is the relaxation time of the polymer at the glass transition temperature ... 

Oefor -motion Hookian Glassy Secondary transition Primary transition Highly elastic rubbery Flow... 

Zelko R, Siivegh K (2004) Comparison of the enthalpy recovery and free volume of polyvinylpyrrolidone during anomalous glassy to rubbery transition. J Pharm Sci 21 519-523. 

Diffusion anomalies are intimately associated with the polymer s glassy/rubbery state transition. Hence, anomalous transport models have been proposed to understand penetration into polymers. 

Considering that the E-modulus of the leathery (Ej) and rubbery (Ej.) states are almost the same (see Chapter 2, the leathery and rubbery states are not discernible based solely on the change in E-modulus), the leathery-to-rubbery transition can be neglected. Therefore, within a unit volume of initial material at a specified temperature, the volume of the material at the different states (glassy, leathery or rubbery, and decomposed) was derived in Eq. (3.3), Eq. (3.4), and Eq. (3.5). Furthermore, after decomposition, the decomposed material no longer has significant structural stiffness. Its modulus, E, can be taken as zero. The following equation can thus be obtained to describe the effective E-modulus ... 

Li, Q. (2010). Investigating the Glassy to Rubbery Transition of Polydextrose and Com Flakes Using Automatic Water Vapor Sorption Instruments, DSC, and Texture Analysis [Thesis]. Urbana, IL University of Illinois at Urbana-Champaign. 

A comprehensive review of measurement techniques is presented by Capps (167), who also gives data for the complex Young s modulus for a range of polymers. This data includes the rubbery, transition, and glassy regions, and parameters for time-temperature superposition (eq. 45). The measiuement techniques fall broadly into three categories wave propagation methods, resonance methods, and forced-vibration nonresonance methods. The resonance and forced-vibration... 

Yuan X, Carter BP, Schmidt S J (2011) Determining the critical relative humidity at which the glassy to rubbery transition occurs in poly dextrose using an automatic water vapor sorption instrument. 

The glass transition generally occurs over a relatively narrow temperature span and is similar to the solidification of a liquid to a glassy state it is not a phased transition. Not only do hardness and brittleness undergo rapid changes in this temperature region, but other properties, such as the coefficient of thermal expansion and specific heat, also change rapidly. This phenomenon has been called second-order transition, rubber transition, and rubbery transition. The word transformation has also been used instead of... 

In a hydrophilic matrix, the glassy soluble polymer transforms into a rubbery state as the water plasticizes it and reduces the T. The glassy/rubbery polymer interface will constitute the swelling (transition) front [9]. 

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