Amorphous non-polar polymers

Amorphous non-polar polymers and amorphous non-polar solvents. 

If we now consider the inequalities given in equations 18.6 to 18.8 it will be seen that compatibility can only occur between amorphous non-polar polymers and solvents when ... 

Amorphous non-polar polymers and crystalline solvents This situation is identical to the previous one and occurs, for example, when paraffin wax is mbced into rubber above its melting point. On cooling the paraffin wax tends to crystallise, some of it on the surface of the rubber. Such a bloom is one way of protecting a diene rubber from ozone attack. 

Crystalline non-polar polymers and amorphous solvents Most polymers of regular structure will crystallise if cooled below a certain temperature, i.e. the melting point T. This is in accordance with the thermodynamic law that a process will only occur if there is a decrease in Gibbs free energy (-AF) in going from one state to another. Such a decrease occurs on crystallisation as the molecules pack regularly. 

Both direct measurements and a wealth of compelling indirect evidence support the random coil, perhaps slightly expanded beyond -dimensions, as the correct description of large-scale chain configuration in amorphous systems of flexible, relatively non-polar polymers. It is certain that neither greatly contracted... 

All these commercially produced BR systems are amorphous rubbers under atmospheric conditions. The Tg-value of these systems, depending on their structure, is described by the Gordon-Taylor relation, see Chapter 1. BR becomes a semicrystalline polymer under atmospheric conditions if the 1,4 trans-BR content is higher than about 70 %wt. or if a syndio-or isotactic 1,2-BR phase is present. This is shown by the results of thermo-analytical measurements on experimental BR systems with a high trans content and with a high syndiotactic 1,2-BR content which are reported in this chapter. Moreover, the Tg-values of two series of IR samples containing 1,2- and 3,4-IR are used to determine the Tg/structure relation for non-polar polymers with side-chains. 

These tables are of greatest use with non-polar materials with values of 8 less than 19.4 MPa and where the polymers are amorphous. It will now be necessary to discuss other systems. 

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