IRAffinity-1S - Applications

Polymeric materials may undergo changes in composition or molecular structure due to such factors as mixing, heating, light exposure, etc. These changes may reach completion within a few seconds or may progress slowly over several hours. An FTIR is useful for conducting analysis of polymer composition and molecular structure, and LabsolutionsIR software, with its included timecourse measurement program, permits tracking of sample peak changes over time.
We introduce an example of measurement of the curing process of polyvinyl chloride resin adhesive using the time-course measurement program.

Time-Course Analysis Program

3D Time-Course Measurement Graph

The sample used here, a thermoplastic resin adhesive consisting of vinyl chloride - vinyl acetate copolymer resin dissolved in an organic solvent (acetone, cyclohexanone), is commonly used for bonding of vinyl chloride pipes, etc.
A single measurement was set to be conducted every 30 seconds over a measurement period of 1800 seconds (30 minutes), assuming zero seconds for sample-drop onto the diamond disk.
The region from 2000 - 550 cm^-1 is shown here as a 3D graph in which the XY axis represents time (sec) and wavenumber (cm^-1), and the Z axis represents absorbance. This permits observation of the sample reaction process over time.

Peak Change Analysis Using 2D Time-Course Data

Time-course measurement also permits the graphic display of absorption changes in peaks of interest as 2D time-course　data. We calculated the curing reaction rate assuming a reaction rate of 0 % at the start of measurement and the completion of the curing reaction 30 minutes later.

When measuring a sample in which the reaction proceeds gradually, this type of time-course measurement effectively provides a variety of data, including peak height, peak area, as well as reaction rate.

We introduce the determination of fatty oil content using an infrared spectrophotometer in accordance with JIS K 2241.

Measurement of Fatty Oil by Single Reflection ATR Spectroscopy

First, to generate the calibration curve, commercially available rapeseed oil was added to liquid paraffin to prepare standards at concentrations of 5.0, 7.5, 10.0, 12.5 and 15.0 % (mass fraction %) according to the JIS procedure. The standard oil samples with different concentrations were thinly coated on the ATR prism, and the spectra were measured.

New Quantitation Program of LabSolutions IR

The quantitative measurement program that is included in the standard LabSolutions IR software permits simple calibration curve generation and quantitation of unknown samples.
JIS K 2241 specifies that "Absorbance is the value expressed by the difference between the peak top
(point at which peak is maximum between 1740 and 1750 cm^-1) in the spectrum and the baseline (a location where the baseline is stable on both sides between 1740 and 1750 cm^-1)." Therefore, we generated a calibration curve using a peak in the vicinity of 1749 cm^-1 and the baseline between 1712 and 1780 cm^-1 for the corrected peak height. The correlation coefficient was greater than 0.9998, indicating excellent results.
After generating the calibration curve, we conducted quant i tat ion of an unknown sample. Here, we analyzed a sample of commercially available water-insoluble cutting fluid. The fatty oil content was calculated to be 10.7 %.

Use of the LabSolutions IR quantitative measurement program makes it easy to generate and store calibration curves, and conduct quantitative analysis of unknown samples. In addition to the quantitation of fatty oil in cutting fluid, a wide variety of quantitative analyses are supported.
Also, for details regarding fatty acid oil testing of cutting fluid, please refer to JIS K 2241 Cutting Fluid (Supplement 1).