Physical transitions in curing systems

Type of pol5mer Temperature Type of irradiation source Dose Chemistry, crystalhnity, density, branching structure Mobility of chains and reaction rates increase with temperature Type of grafting/crosslinking reaction possible, depth of cure penetration Number of reaction sites increases with dose 

The aim of this book is not to discuss each of these reactive modification techniques in detail, but rather to show how chemorheology can be a useful tool from fundamental understandings to understanding processing, process control and optimization. 

To control the final properties of reactive polymers it is essential that the curing of the polymer is well characterized. This means that it is necessary to have a good knowledge of how the materials transform from the original monomeric or polymer matrix to the final cured polymer. Thus it is self-evident that the curing transitions of a system are very 

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In this diagram the x-axis is the extent of cure (Tg) and the y-axis is the temperature. The properties of the curing system may be separated into distinct regions of the glass transition (Tg), the beta-transition (P-Tg), the end of the glass transition (s Tg) and gelation (Tg g i). Properties may also be implied on the third axis out of the plane of the paper. Thus the physical properties (behaviour) of a system with respect to conversion are determined by its temperature and Tg. 

Table III shows the reactivity properties of the molding powder and the physical properties of the cured compound. This table indicates there are virtually no differences in gel times, flow properties, flexural properties, moisture absorption, flame retardancy, and glass transition temperatures between the compound based on stable bromine CEN and the compound based on the standard system of CEN and the epoxy of TBBA.

Consequent to documentation surrounding methods of employing reactive nitrile elastomers to modify epoxy resins is a growing body of literature which serves to characterize and elucidate these systems. Such topics as morphology in the cured and uncured state, transitions from toughening to flexlbilization, viscoelastic effects, equilibrium physical properties and phase structure are available to the investigator (12-17). 

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