Glass transition temperature phenomenon

The iatroduction of a plasticizer, which is a molecule of lower molecular weight than the resia, has the abiUty to impart a greater free volume per volume of material because there is an iucrease iu the proportion of end groups and the plasticizer has a glass-transition temperature, T, lower than that of the resia itself A detailed mathematical treatment (2) of this phenomenon can be carried out to explain the success of some plasticizers and the failure of others. Clearly, the use of a given plasticizer iu a certain appHcation is a compromise between the above ideas and physical properties such as volatiUty, compatibihty, high and low temperature performance, viscosity, etc. This choice is appHcation dependent, ie, there is no ideal plasticizer for every appHcation. 

Glass-Transition Temperature. When a typical Hquid is cooled, its volume decreases slowly until the melting point, T, where the volume decreases abmpdy as the Hquid is transformed into a crystalline soHd. This phenomenon is illustrated by the line ABCD in Eigure 3. If a glass forming Hquid is cooled below (B in Eig. 3) without the occurrence of crystallization, it is considered to be a supercooled Hquid until the glass-transition temperature, T, is reached. At temperatures below T, the material is a soHd. 

Detection of glass transition temperatures in several NOMs has further supported the concept of dual mode sorption, a phenomenon occurring in synthetic... 

An unusual and exciting phenomenon is observed in certain iron containing oxide glasses under a thermal treatment above the glass transition temperature Tg. The well-known feature at gc ps 4.3 in the X-band EPR... 

It must be emphasized that polymer adhesion is a complex phenomenon. The efficiency of an adhesive is only partly determined by interfacial properties. Cassidy et al. (1972) already found that effects on the glass transition temperature of the adhesive may be more important than interfacial properties. An additive that lowers Tg from a point above the test temperature to below it, causes a decrease in the strength of the system with cohesive failure within the adhesive. 

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