GB/T 47392-2026Plastics - Epoxy resins - Determination of degree of crosslinking of crosslinked epoxy resins by Fourier Transform Infrared (FTIR) Spectroscopy (English PDF)

1 Scope

This document describes a method for the determination of the degree of crosslinking of epoxy resins by Fourier transform infrared spectroscopy.

This document applies to the determination of the degree of crosslinking of epoxy resins by Fourier transform infrared spectroscopy.

2 Normative references

There are no normative references in this document.

3 Terms and definitions

For the purpose of this document, the following terms and definitions apply.

3.1 degree of crosslinking

Value indicating the degree of crosslinking of an epoxy resin.

NOTE 1.See formula (4) in Clause 8.

NOTE 2.It is expressed as a percentage.

3.2 height of absorption peak

Maximum distance on the ordinate direction between the virtual baseline and the

Fourier transform infrared spectral absorption peak.

NOTE 1.The virtual baseline is simply drawn by connecting the peak start and peak end point by a straight line.

NOTE 2.When a specified peak cannot be completely separated from other peaks, the virtual baseline is drawn by optionally selecting a peak start and a peak end point from among multiple peaks, including the specified peak, and connecting them by a straight line.

3.3 peak height ratio

Value calculated by dividing the peak height of the epoxy group absorption (wave number 900 cm^-^1 to 915 cm^-^1) by the peak height of the internal standard group absorption, which is not changed by a crosslinking reaction.

NOTE. It is recommended to use the methylene group absorption band (approximately 2930 cm^-^1) as the internal standard group absorption peak.

4 Principle

It is determined by the peak height ratio of the absorption peak of the crosslinked epoxy resin to the non-crosslinked epoxy resin measured by Fourier transform infrared spectrometer (FTIR).

The height of the epoxy group absorption peak (Pa1) and the height of the internal standard group absorption peak (Pa2) in a non-crosslinked epoxy resin sample (see

Figure 1) are measured by FTIR.

The peak height ratio (X) of the non-crosslinked state is calculated in accordance with formula (1).

The height of the epoxy group absorption peak (Pb1) and the height of the internal standard group absorption peak (Pb2) in a crosslinked epoxy resin sample (see Figure

2) are measured by FTIR.

The peak height ratio (Y) of the crosslinked state is calculated in accordance with formula (2).

The degree of crosslinking is determined in accordance with formula (4) in Clause 8.

Figure 1 -- Spectrum of non-crosslinked epoxy resins

Figure 2 -- Spectrum of crosslinked epoxy resins

5 Materials and crosslinking conditions

6 Apparatus

6.1 Fourier transform infrared spectrophotometer, with the following characteristics.

a) an operating wavenumber range. 4000 cm^-^1 ~ 650 cm^-^1;

b) the capable cumulative peak count shall exceed 16.

6.2 Micropipette, with capacity 1 µL ~ 10 µL.

6.3 Silicon wafer, with the following characteristics.

a) single-sided polished monocrystalline silicon wafer;

b) thickness of 625 µm ± 15 µm;

c) total thickness variation (TTV) of 10 µm;

d) total dimensions of the wafer (150 mm wafer);

e) dimensions of the square silicon wafer for testing. 15 mm (±2 mm) × 15 mm (±2 mm).

NOTE. The square silicon wafer for testing is cut from a wafer (see 6.3 d) or a finished silicon wafer meeting specifications can be used.

6.4 Analytical balance, with accuracy 0.1 mg.

7 Test procedure