Thermal aging studies

Patel, M. Skinner, A. R. (2001) Thermal ageing studies on room-temperature vulcanised polysiloxane rubbers. Polymer Degradation and Stability, 73, 399-402. 

Brett, K. M., and Burford, R. R, Thermal aging studies of conducting polypyrroles,... 

Bhargava S, Kubota M, Lewis RD, Advani SG, Prasad AK, Deitzel JM. Ultraviolet, water, and thermal aging studies of a waterborne polyurethane elastomer-based high reflectivity coating. Prog Org Coat 2015 79 75-82. 

The major difficulties involved in making electrically conductive thermoplastic blends using polyaniline, polypyrrole, or their composites, are two-fold. The first is the thermal instability of doped polyaniline and polypyrrole at melt processing temperatures (1-3), The second is the chemical incompatibility of acidic conductive polyaniline with acid sensitive polymers such as the nylons. Conductive polyaniline is quite acidic and the adjustment of its acidity to neutral pH values eliminates its high conductivity (4,5). The authors present here thermal aging studies of conductivity and thermal gravimetric analysis - mass spectroscopy (TGA-MS) of Eeonomers which show pH independence of conductivity in acidic to neutral environments. The tunable surface properties of Eeonomer composites allows one to optimize the processibility as well as the electrical and mechanical properties of their blends with various thermoplastics. 

Thermal aging studies to support the irradiation study (ORNL)... 

More recently Patel ef a/. [19,20] have carried out accelerated thermal aging studies (over a temperature range of 50- 190 C) on commercicil room temperature vulccuiized, diatomaceous earth filled sihcone elastomer systems. Thermo-mechanical analysis demonstrated that significant stress relaxation (a time-dependent decrease in stress under an applied strain) of the silicone network took place under the conditions of the study. Application of the time-temperature superposition principle and Arrhenius methodology to the data strongly... 

Structure—Property Relationships The modem approach to the development of new elastomers is to satisfy specific appHcation requirements. AcryUc elastomers are very powerhil in this respect, because they can be tailor-made to meet certain performance requirements. Even though the stmcture—property studies are proprietary knowledge of each acryUc elastomer manufacturer, some significant information can be found in the Hterature (18,41). Figure 3a shows the predicted according to GCT, and the volume swell in reference duid, ASTM No. 3 oil (42), related to each monomer composition. Figure 3b shows thermal aging resistance of acryHc elastomers as a function of backbone monomer composition. 

The effect of thermal aging on polyethylene and isotactic polypropylene have been studied by Konar et al. [49]. They used contact angle, contact angle hysteresis, and XPS to characterize the modified surfaces of the polymers. Hysteresis increased with aging temperature. In the case of polyethylene, thermal aging led to a significant increase in adhesion strength of polyethylene with aluminium, but the increase in the case of polypropylene was much less marked. 

The present study was initiated to understand the causes of large differences in perfonnance of various catalyst formulations after accelerated thermal aging on an engine dynamometer. In particular, we wished to determine whether performance charaderistics were related to noble metal dispersion (i.e. noble metal surface area), as previous studies have suggested that the thermal durability of alumina-supported Pd catalysts is due to high-temperature spreading or re-dispersion of Pd particles [20-25]. 

P. Dietemann, M. Kahn, S. Zumbuhl, R. Knochenmuss, S. Wiilfert, and R. Zenobi, A Mass Spectrometry and Electron Paramagnetic Resonance Study of Photochemical and Thermal Aging of Triterpenoid Varnishes, Anal. Chem., 73, 2087 2096 (2001). 

Properties such as friction, gas permeability and thermal conductivity are only likely to have significant importance in specialised applications and it is not surprising that they are very rarely measured in ageing studies. 

The phenyl modified polymers possess the optimum combination of high temperature and elastomeric properties and were used in the study of formulation parameters These variables can have an important effect on the thermal stability and property profile of vulcanized systems For example, the use of reinforcing silicas, peroxide content, and oxidative stabilizers have been shown to be important ( 3, 10, in However, polymer-silica interactions had the most pronounced effect on retaining properties during high temperature aging studies ... 

Characterization. Differential scanning calorimetry and thermal mechanical analysis data were obtained on a DuPont 990 thermal analyzer coupled with a DuPont DSC or TMA cell. Isothermal aging studies were carried out with an automatic multisample apparatus. 

Dietemann P, Kahn M, Zumbiihl S, Knochenmuss R, Wiilfert S, Zenobi R (2001) A mass spectrometry and electron paramagnetic resonance study of photochemical and thermal aging of triterpenoid varnishes. Anal Chem 73 2087-2096. 

Diels-Alder mechanism. It was found that those polymers which had the least weight loss in the isothermal aging study were derived from those monomers which by DSC polymerized to the greatest extent by a Diels-Alder mechanism. It was inferred therefore that if similar considerations apply to the copolymers of bismaleimides and bisbenzocyclobutenes then these materials too might be the result of predominantly Diels-Alder type polymerizations. To the extent to which these conclusions are correct, the enhanced thermal stability of the bisbenzocyclobutene/bismaleimide copolymers is likely to be due to their being Diels-Alder polymers of some sort. 

Of all the high temperature, high performance polymers, the benzobisazole rigid-rod polymers are one of the most thermally stable systems known. A variety of thermal techniques have been used to investigate their stability such as thermal gravimetric analysis (TGA), thermal gravimetric-mass spectrometry (TG-MS) and isothermal aging studies. A TGA plot shown in Fig. 4 is indicative... 

Thermal aging has also been widely studied for its technological interest, but most of the studies are empirical or semiempirical (using, e.g., the Arrhenius law and an arbitrary end-life criteria, from mass-loss kinetic curves). Powerful conceptual tools (radical chain kinetics, coupled diffusion-reaction schemes, etc.) are available to avoid or, at least, to reduce significantly the empiric approaches. 

Chiou KL, Kyle LE. Differential thermal, solubility and aging studies on various sources ofdigoxin and digitoxin powder biopharmaceutical inplications. J Pharm Sci 1979 68(10) 1224-1229. 

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