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Characterization of polar materials by Dielectric Analysis (DEA) (CAT#: STEM-ACT-0086-WXH)

Introduction

A polar material in the strict (crystallographic) sense is a material containing a nonvanishing dipole moment. All such materials are in principle pyroelectrics, i.e., found in the pyroelectric, or now more conveniently called “polar,” point groups.<br />Examples of polar plastics are PMMA, PVC, PA (Nylon), PC and these materials tend to be only moderately good as insulators.




Principle

The term dielectric analysis (DEA) refers to a group of techniques that measure changes in different physical properties of a polar material, such as polarization, permittivity, and conductivity, with temperature or frequency. DEA is a materials science technique similar to dynamic mechanical analysis except that an oscillating electrical field is used instead of a mechanical force.
Dielectric Analysis (DEA), also known as Dielectric Thermal Analysis (DETA), is a technique for monitoring changes in viscosity and the cure state of thermosetting resins, adhesives, paints, composites and other kinds of polymers or organic substances by measuring variations in their dielectric properties.
In dielectric thermal analysis, an oscillating AC electrical field is applied to a sample of material, and measurements of the material’s capacitance and conductance are taken as a function of time, temperature and frequency. Some of the electrical charge will be stored in the material sample (capacitance) and the rest of the electrical charge will be dissipated through the material sample (conductance). The relaxation properties of the material sample will determine the sample’s rates of capacitance and conductance.

Applications

This technique has been widely applied to study the molecular structure, degree of polymerization and polymer mechanism of material dielectrics.
In terms of application objects, there are thermoplastic and thermosetting resins such as polyacrylate, polyvinyl chloride, polyamide, polyimide, polystyrene, phenolic, epoxy, and polywax. In addition, there are polyphenyl maple and polybenzimidazole in high temperature resistant resins, and proteins in biological compounds. Its specific applications also include reinforced plastics, molding materials, coatings, adhesives, rubber and even metal oxides such as glass and ceramics.
In the laboratory, the DETA can be used as a powerful tool for viscoelastic studies, such as dynamic mechanical properties and thermomechanical property tests. In industrial production, it can be used in resin manufacturing, quality control, pre-curing and degree of cure control.

Materials

Testable materials: Thermosetting resin systems, adhesives, paints, and composite materials