How a polymer goes under glassi state and crystilization and melting state?
Answers
C. Austen Angell, Shanmugasundaram Sivarajan, in Reference Module in Materials Science and Materials Engineering, 2017
Abstract
Glass transition refers to the transformation in a system upon cooling from a super cooled liquid state to a non-equilibrium disordered glassy state. Glass transition is often caused by variations in pressure, temperature and other thermodynamic control parameters. Analytical and experimental studies of glass transition are important due to widespread applications of glass in everyday life. This article describes the glass transition temperature, transformation range, methods of detecting glass transition, determination of glass temperature and thermodynamic relations at the glass transition. The recent developments in the modeling of glass transition are also presented.
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Mapping the Different States of Food Components Using State Diagrams
Yrjö H. Roos, in Modern Biopolymer Science, 2009
Although novel thermal analytical and spectroscopic techniques allow detection of the glass transition, relaxations and molecular mobility associated with the transition, numerous empirical methods are commonly used to observe changes in flow resulting from the change in molecular mobility and the state of the material around the glass transition. Examples of empirical measurements of solid to liquid changes in foods are the observation of sticky points of powders (Lazar et al., 1956) and measurements of collapse in frozen (Bellows and King, 1971) and dehydrated systems (To and Flink, 1978a, 1978b, 1978c). The state diagrams with glass transitions and relaxations data have advanced understanding of the relationships of the various methods. The state diagrams also explain differences in various time-dependent characteristics of materials associated with empirical observations of material properti
THE GLASS TRANSITION PHENOMENON
W. Shakespeare, in Structural Chemistry of Glasses, 2002
Understanding glass transition phenomenon is of primal importance in the study of glasses. In chapter 2, the general features of glass transition were introduced. In this chapter, various approaches made towards explaining this phenomenon are discussed. To begin with, we note that in the supercooled region the viscosity increases exponentially to values as high as 1013.6 poises. At this stage the supercooled liquid rapidly transforms into a glass, although viscosity itself suffers no discontinuity at Tg. Nevertheless one should expect a proper theory of viscosity of liquids to be able to account for the glass transition and associated features. The first major development in this direction has been the formulation of free volume theory of liquid viscosities.
Chemical and photophysical properties of materials for OLEDs
Z. Dechun, in Organic Light-Emitting Diodes (OLEDs), 2013