Characterization Analysis of Polymers

As an important type of material, polymers play key roles in our daily life. Polymers are made up of small molecular units, and these small molecular units are called monomers. Monomers of polymer can be joined together either naturally or synthetically. Cellulose is a familiar natural polymer that can be used in textile industry. With the development of synthetic technique, production of synthetic polymers soared. Synthetic polymers surround our daily life, such as water pipelines, car tires/bumpers, some drinking cups, water pipelines, containers, clothes and shoes, cellphone, etc. Different materials need different properties, and polymers obtained from different synthetic technology usually possess different performances. Therefore, characterization analysis of polymers is a very significant aspect for polymer industry.

Nowadays, many characterization analysis methods have been developed, and they are playing important roles in practical applications. These methods can analysis molecular weight, thermal properties, mechanical properties, microscopic information, inter/intra molecular interactions, etc.

Table 1. General methods for polymer characterizations

Differential Scanning Calorimeter (DSC)

A differential scanning calorimeter (DSC) is a thermal analytical technique, which can reveal the thermal properties (heat capacity, glass transition T_g, crystallization degree) of a polymer. DSC can be used to measure heat capacity, identify unknown polymer/additives (blends, fillers, plasticizers, process aids), estimate crystallinity percentage, determine process temperatures (cure, injection/ extrusion/thermoforming molding, heat welding), monitor aging/oxidation effects, etc.

Fig.1 DSC transformation temperatures and phase transformations for a material¹

Thermal Gravity Analysis (TGA)

As another important thermal analytical technique, Thermal Gravity Analysis (TGA) measures the mass of a sample over time with the temperature changes. This characterization analysis method offers information about physical phenomena, such as absorption, desorption and phase transitions; as well as chemical phenomena including solid-gas reactions and thermal decomposition.

Gel Permeation Chromatography (GPC)

Gel Permeation Chromatography (GPC) also called Size Exclusion Chromatography is used to identify the relative molecular weight of polymer samples as well as the distribution of molecular weights. The distribution of molecular weight is a very important factor that will determine the performance of a polymer material, including chemical and physical properties.

Fig.2 An example of GPC²

Fourier Transform Infrared Spectroscopy (FTIR)

By analyzing the peaks’ position and shape in Fourier Transform Infrared Spectroscopy (FTIR), the inter/intra molecular interaction information of polymers can be obtained, which is very valuable information for material modification.

Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM)

Scanning Electron Microscope (SEM) and Transmission Electron Microscope (EM) are very powerful instruments that can reveal the microscopic information of a polymer, and different microscopic information can also influence the chemical and physical performance of a material.

Fig.3 An example of SEM of a polymer³

Universal Testing Machine

Mechanical properties are critical for materials especially for building material. Universal testing machine is a desired machine that can be used to test the tensile strength and compressive strength of polymer materials.

Fig.4 An example of universal testing machine testing result⁴

In summary, so far there have been many methods to characterize polymer properties. Reasonable use of these characterization analysis method is very beneficial for technology improvement, scientific study and quality control.

References

• A Arias, JC Macorra, S Govindjee, OA Peters. (2018) ‘Correlation between Temperature-dependent Fatigue Resistance and Differential Scanning Calorimetry Analysis for 2 Contemporary Rotary Instruments’, Journal of endodontics. 44(4):630-634

• MasayukiKawahigashi, NobuhideFujitake, JunzoAzuma, TakehikoTakahashi. (1995) ‘Preparation of humic acid fractions with a definite range of particle sizes by gel permeation chromatography (GPC)’ Soil Science & Plant Nutrition. 41(1):147-150.

• RA Shelden, LP Meier, WR Caseri, UW Suter, R Hermann. (1994) ‘Nanophase molecular droplets: individual polystyrene molecules on mica imaged with scanning electron and atomic-force microscopy’, Polymer. 35 (8):1571-1575.

• Naik N K, Yernamma P, Thoram N M,, (2010) ‘High strain rate tensile behavior of woven fabric E-glass/epoxy composite’, Polymer Testing, 29(1):1

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