FTIR

Introduction of FTIR

FTIR is widely used to identify the chemical structure of compounds, especially the information of chemical bonds and functional groups, due to simple operation, simple sample preparation, various sample state and shape and high repeatability. At the same time, by FTIR, rapid and precise measurement in a wide range can be achieved with high resolution. Therefore, FTIR is developing rapidly to almost replace the traditional infrared spectrum.

FTIR involves the study of the interactions between molecules and IR light. When a sample is irradiated with IR light, light with a certain wavelength will be absorbed to stimulate vibrational and rotational energy transitions, for which the light intensities will decrease. Various molecular structures exhibit own energy differences, corresponding to different IR wavelengths ^[1]. An IR spectrum is obtained by plotting transmittance or absorbance versus the wavenumber of IR light. The position, intensity, and shape of the peaks reflect the characteristic vibrational frequencies, functional groups or chemical bonds. Therefore, FTIR can be used to qualitatively analyze the chemical bonds or functional groups of a compound ^[1].

Data of FTIR

Figure1: Infrared spectrum of EVA copolymer^[2].

In this figure, the Y axis represents the absorptivity (%), and the X axis represents 10² wavenumber (cm^-1).

Discussion of FTIR

In the infrared spectrum of EVA copolymer, there are absorption peaks of ethylene and vinyl acetate^[2].

Wavenumber of 2850-2950 cm^-1, the peak is the stretching vibration absorption peak of saturated C-H bond.
Wavenumber of 720 cm^-1, the peak is the bending vibration absorption peak of (CH₂)_n (n > 4).
Wavenumber of 1735 cm^-1, the peak is the stretching vibration absorption peak of double bond in ester carbonyl.
Wavenumber of 1245 cm^-1, the peak is the stretching vibration absorption peak of single bond in ester carbonyl.

These absorption peaks indicate the existence of specific chemical bonds and functional groups, from which the chemical structure of EVA can be qualitatively analyzed as including saturated C-H, (CH₂)_n (n > 4) and ester groups. From the aspect of structure, EVA does not contain unsaturated bond and the active site which is extremely sensitive to the environment, which makes EVA not absorb water, but also has resistance to acid, alkali, sea water, cold and heat. Therefore, EVA is an ideal material for making waterproof board and packaging materials.

Ethylene-vinyl acetate copolymer (EVA)

Ethylene-vinyl acetate copolymer (EVA)

Characterization Data for Ethylene-vinyl acetate copolymer (EVA)

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