Mechanical Characterization of two Amorphous Polymers in Traction-Compression Test using A Viscoelasticimeter
Abstract
Using the viscoelasticimetric tests in traction and compression mode, the viscoelastic sizes E’, E" and tan were characterized according to the temperature and this, for amorphous polymer samples differentiated by their fluidity index. It is noted that the stiffness is intermediate size making it possible to characterize the conservative components E’ easily and the dissipative one E" of the module complexes E* like its temperature of glass (vitreous) transition from polymer trough the factor of loss tan. These sizes in comparison with the abundant data by the manufacturers make it possible to consolidate the mode of request retained:
The temperature of vitreous transition Tg obtained on the two samples from methylpolymethacrylate (PMMA) in modetraction compression is integrated in the interval of temperatures (110 to 135°C) advised by the manufacturers of this material.
The ranks of polycarbonate (PC) tested in the two modes had a constancy of behaviour with Tg quasi equivalent to150°C with a variation of 5°C.
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Introduction
The behavior of polymeric materials, by taking temperature as a descriptive variable of their hierarchization, makes it possible to specify in particular the domain of their specific properties which concern:
The solid-state viscoelastic materials associated with the notion of rigid-rubber transition,
The more intuitively characteristic flows of a viscous liquid state.
These two aspects define the rheological behavior of these materials and we simply recall that rheology is, as a first approach, the science that studies the evolution of the deformation and flow of condensed phases under imposed stress. In practice, the dependent parameter may be in addition to the temperature, the deformation or the rate of deformation.
In addition, pasty solid-solid, solid-solid, viscous solid, viscous-liquid solid, solid-liquid, liquid-liquid solid passages are sometimes difficult to apprehend. This is explained by the fact that these different state phases are sometimes a function of the temperature of the test, the mode of loading and the time of application.
Conclusion
The representation of the different viscoelastic quantities (E ', E ", tan) of each material as a function of temperature (see Fig. 3 to 8) made it possible to differentiate the behavior of the polymers of distinct melt index.
For all the results obtained by the tensile-compression mode tests on the different amorphous polymers (PMMA, PC), it was found that the evolution of the loss factor tan qualifying the glass transition temperature (Tg) by a maximum peak has been used to record Tg supporting the theoretical data provided in the technical brochures and in the literature [1, 4, 10, 21, 23].
The values recorded could be associated with the Vicat softening temperatures of the material.
In a global way, the variation of the conservative modulus E '= f (T) allowed, whatever the material tested in traction - compression mode, to identify three domains of behavior:
elastic-vitreous where the rigidity of the polymer is observed,
viscoelastic in which the amplitude of E "and the Tg are recorded,
elastic - rubbery.