Análises térmicas em sistemas poliméricos: uma ferramenta para a avaliação da degradação
Abstract
In the contemporary world, the demand for polymeric materials has grown
intensely to meet the pace of consumption. In view of this, concern about the disposal
of polymers becomes an issue when considering waste management. Thus,
investigating the impact of degradation on the physical and chemical properties of
these materials by means of thermal analyses is a possible approach to this problem.
To accomplish this, this study was structured to introduce basic concepts on the subject
as well as address the degradation mechanisms undergone by polymers and their
precursor agents, refer to the impacts of degradation on the properties of some
polymeric systems, and discuss the fundamentals, characteristics, and parameters of
thermal analyses. Thermal analyses are a group of various techniques that measure
the physical and chemical properties of a given material as a function of temperature
under controlled atmospheric, heating and cooling conditions. The properties of the
sample are analyzed by monitoring the changes in the material as a function of time
and temperature compared to a reference, which makes it possible to determine
certain physical and chemical properties of the material in order to determine its
possible applications, storage, behavior, and transport. For this work, the focus will be
on Differential Scanning Calorimetry (DSC) analyses, which monitor the flow of heat
through the sample over time and temperature. With DSC it is possible to determine
the Vitreous Transition Temperature (Tg), Crystaline Melting Temperature (Tm) and
Crystallization Temperature (Tc), the melting enthalpy (∆Hf), degree of crystallinity (Xc),
specific heat, phase transition, curing and crystallization kinetics. And
Thermogravimetric Analysis (TGA), which relates the change in mass in a sample
under a controlled atmosphere; it investigates the thermal decomposition profile of the
material. With TGA, we can study the thermal stability of the sample, thermal
decomposition, moisture content and pyrolysis of certain substances. This work will
conclude with a discussion of two case studies. The first one will address the use of
thermal analyses to understand the effects of degradation on Nylon 6,6, while the
second will investigate the durability of cables in nuclear plants.
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