Plasticization inverse effect

A contributing factor was thought to be the weakening effect of residual stresses resulting from the crystallographic inversion from the monoclinic to the denser thermodynamically stable orthohombic form on cooling below 95.5°C. Attempts to improve durability have therefore been based on plasticization of the sulphur. The intention is to reduce brittleness and lower the level of internal stress (J>, 13, 14, 15, 16). 

Proc. First International Particle Technology Forum, vol. 2, AIChE, Denver, 1994, p. 178), whereas surface energy can be characterized by inverse gas chromatography and other adsorption techniques. Particle yield pressures and elastic moduli of the powder feeds can also be determined by uniaxial compaction experiments which monitor deformation and pressure throughout the compaction cycles. In addition, rate effects are investigated, as plastic and elastic properties can be rate-dependent for some materials. 

The increase in the TD density in the films grown on relatively thick (6-8 pm) PSC is most probably caused by a specific plastic relaxation process, occurring as a reaction to a particular state of strain that appears in these epitaxial films. This can be stated on the basis of strain inversion in the films grown on PSC, as well as on the increase in compressive stress with the thickness of the PSC layer increasing. These effects show that apart from the stress caused by the GaN/SiC lattice mismatches, an additional built-in stress arises in the films. Obviously, the additional stress is caused by the presence of (0001) PDs, because one can expect that a part of GaN film within the faulted region may have altered its mechanical properties as compared with unfaulted material [72]. Then the increase in dislocation density in GaN grown on relatively thick PSC can be explained by a plastic relaxation process, which relieves the built-in stress and occurs because this internal stress/(0001) PD density reaches a certain critical value. 

The presence of dissolved CO2 molecules in a polymer results in the plasticization of the amorphous component of the matrix. In this respect CO2 mimics the effect of heat but with the important distinction that the Tg is depressed. The extent of the Tg depression is dependent on the wt% of CO2 in the matrix. As previously mentioned, one of the characteristics of plasticization is the enhancement of segmental motion, which has been observed spectroscopically for the ester groups of PMMA [20] and the phenyl rings of polystyrene [21]. The consequential increase in free volume of the matrix has been studied by methods such as laser dilatometry [22], in situ FTIR spectroscopy [20], high-pressure partition chromatography [23], and inverse gas chromatography [24]. 

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