Glass transition temperature broadening

If highest resolution is required, then the strategy is to use thermal activation to stir away the conformatonal anisotropy operate as close to the glass transition temperature as possible, up to the point at which Ti lifetime broadening predominates. On the other hand, at lower temperatures the lineshape and its temperature dependence may provide useful information (34). 

Another study that focussed on the glass transition temperature of such composites revealed that the a-relaxation in the acrylonitrile/ styrene phase is broadened towards higher glass transition temperatures. It is believed that the shift arises due to the interaction located at the boundary layer between polymer and CNTs (51). 

Struik also (1987-1989) showed that his concept of physical ageing and its affects on the mechanical behaviour can be extended to semi-crystalline polymers the only additional assumption needed is that in semi-crystalline polymers the glass transition is broadened and extended towards the high temperature side. Fig. 13.55 illustrates this. 

Differences in tacticity were also reflected by thermal data. While the iso-tropization temperature of (-)-poly-(IV-ll) and ( )-poly-(IV-ll),synthesized using initiator 1, stayed approximately unchanged, the isotropization temperatures for the chiral liquid crystalline polymers shifted to higher values when initiators 2 or 3 were used. The difference was up to 7 °C. If the decreased glass transition temperatures (Tg) for the chiral analogues were taken into account, the temperature range of the liquid crystalline phase was broadened by up to 12 °C. This means that a certain diad must be responsible for this behavior. The authors assumed that the diad cmHT was most suitable one for the formation of stable liquid crystalline phases in poly(norbornene) main chains. 

Dynamic thermal mechanical analysis indicates significant broadening of glass transition temperature at or around PU/EP composition of 70/30. This is true for all three groups studied. At this composition, storage modulus showed much less steep variations with temperature during the transition from glassy to rubbery state. 

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