DYNAMIC THERMAL STABILITY

PVC/EPR exhibits good processability as shown by fluidity, homogeneity, hot tenacity of the melt, specific power absorption, and dynamic thermal stability. 

Fig. 19. Dynamical thermal stability of electric field poling-induced electro-optic activity for two samples. The data were obtained as described in [121] by slowly increasing temperature while monitoring second harmonic generation. The chromophore is a DEC chromophore described in [138]. Uncrosslinked refers to the precursor polymer where only one end of the DEC chromophore is attached to the polymer lattice. Crosslinked refers to the situation where both ends of the DEC chromophore have been reacted to achieve covalent coupling to the polymer lattice. The ends of this DEC chromophore are asymmetrically functionalized so that attachment reactions can be carried out independently...

Fig. 21. Dynamic thermal stability [121] of a variety of polymeric electro-optic materials. All materials involve the Disperse Red chromophore. Trace 1 PMMA composite material trace 2 chromophore covalently attached by one end to a soft (PMMA-like) matrix [138] trace 3 DEC chromophore with both ends attached to a soft polymer matrix [138] trace 4 Disperse Red chromophore covalently attached at one end to a polyimide polymer matrix [121] trace 5 DEC-type chromophore with both ends attached to a sol-gel type matrix [139]...

Polybutene has also been shown to improve impact resistance and dynamic thermal stability in impact modified PVC-U formulations (433). 

The addition of polybutene to impact modified PVC formulations reveals improved impact resistance and increased dynamic thermal stability in the PVC formulation. Polybutene added at levels up to 10% of the total impact modifier gives a significant increase in the Izod impact and increase in dynamic thermal stability by as much as 25%. 6 refs. 

It is also noteworthy that the use of an all-Dianol system has had the effect of increasing the maximum temperature for dynamic thermal stability from 140 to 170°C with the CHDI-based TPU. 

FIGURE 19 The thermal stability of a cross-linked DEC chromophore containing NLO polymer is assayed both by the dynamic thermal stability (temperature ramping) method of Fig. 18 and by measuring the electro-optic coefficient for a sample maintained at a temperature of 100°C for 1000 h. 

The Dynamic Thermal Stability Time (DTST) is a good index for evaluating the thermal stability. DTST is the time at which the torque in a mixing test at constant temperature starts to rise. The material, therefore, must be processed for times lower than DTST. 

In a current rheological study [296], the galactoxyloglucan from Hymenia courbaril was mixed with starch containing 66% amylose and with waxy corn starch (amylopectin). The gel mixtures showed, under static rheological conditions, an increase in paste viscosity compared to those of the polysaccharides alone. Dynamic rheometry indicated that the interactions resulted in increased thermal stability of the gel formed in comparison to that of the starch alone. 

Several enzymes have been immobilized in sol-gel matrices effectively and employed in diverse applications. Urease, catalase, and adenylic acid deaminase were first encapsulated in sol-gel matrices [72], The encapsulated urease and catalase retained partial activity but adenylic acid deaminase completely lost its activity. After three decades considerable attention has been paid again towards the bioencapsulation using sol-gel glasses. Braun et al. [73] successfully encapsulated alkaline phosphatase in silica gel, which retained its activity up to 2 months (30% of initial) with improved thermal stability. Further Shtelzer et al. [58] sequestered trypsin within a binary sol-gel-derived composite using TEOS and PEG. Ellerby et al. [74] entrapped other proteins such as cytochrome c and Mb in TEOS sol-gel. Later several proteins such as Mb [8], hemoglobin (Hb) [56], cyt c [55, 75], bacteriorhodopsin (bR) [76], lactate oxidase [77], alkaline phosphatase (AP) [78], GOD [51], HRP [79], urease [80], superoxide dismutase [8], tyrosinase [81], acetylcholinesterase [82], etc. have been immobilized into different sol-gel matrices. Hitherto some reports have described the various aspects of sol-gel entrapped biomolecules such as conformation [50, 60], dynamics [12, 83], accessibility [46], reaction kinetics [50, 54], activity [7, 84], and stability [1, 80],... 

Carmon, T. Yang, L. Vahala, K. J., Dynamical thermal behavior and thermal self stability of microcavities, Opt. Express 2004, 12, 4742 4750... 

A number of methods have been developed for the determination of the thermal decomposition kinetics of organic and inorganic materials. These include both isothermal and dynamic TGA method28-30 Our studies of the thermal stability of the thermoset polymer utilized isothermal evaluation of zeroth-order decomposition rate kinetics.19... 

The surface nethoxyl groups on the modified catalyst were measured by i.r. spectroscopy and their thermal stabilities were studied by Temperature-Programmed Decomposition (TPDE) in Ar. The surface acidity was measured by TPD of irreversibly adsorbed ammonia and by pyridine adsorption by dynamic method and i.r. spectroscopy. 0.10 g pretreated catalyst was used to measure the amount of irreversibly adsorbed pyridine. The irreversibly adsorbed ammonia was... 

Rosenberg, A. and Somogyi, B. (1986) Conformational fluctuations, thermal stability and hydration of proteins, studies by hydrogen exchange kinetics. n Dynamic of Biochemical systems, edited by S. Damjanovich, T.Keleti and L.Tron, pp. 101-112. Amsterdam Elsevier. 

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