Author(s)Ansunman Mahato & Alan Brookes

Agilent Technologies India & EMEA

ACCURATE MOLECULAR WEIGHT DETERMINATION OF POLYETHER POLYOLS BY TRIPLE DETECTION GPC

MATERIALS MARKET

2

Polyether polyols are polymerized products produced by the catalyzed addition of monomers of propylene oxide (PO) and/or ethylene oxide (EO) to an initiator. Typical initiators are glycerin, mono-propylene glycol, sucrose, sorbitol, water and amines. They are organic materials with two or more alcohol (hydroxyl) groups (OH) at the end of the polyether chains. Polyols of varying molecular weight, functionality, viscosity and reactivity can be produced. They are liquid at room temperature, sometimes with micrometer polymer particles present in suspension. Accurate molecular weight determination for these polymers is essential as the ambiguity in molecular weights changes the physical property of the end product. GPC with Triple Detection is an excellent technique for the analysis of polymers.

ABSTRACT

Mobile Phase THF

Columns

2x PLgel 5 μm MiniMIX-D, 250 x 4.6 mm (PL1510-5504)1x PLgel 5 μm MiniMIX-D Guard, 50 x 4.6 mm (PL1510-1504)

Standards Polystyrene Low EasiVials (4ml), PL2010-0400, Batch: 0006184914

Temperature 40 ˚C (column and detectors)Injection volume 100 μLFlow Rate 0.4 ml/minSoftware Agilent GPC/SEC software

INTRODUCTIONPolyether polyols, when combined with di-isocyanates, are used in urethane applications, such as flexible foam, coatings, adhesives, sealants and elastomers. As a result, we see them in a wide variety of goods including furniture, car seating, coatings, artificial sports tracks, playground surfaces, and waterproof leisure wear. Polyether polyols are also used in non-urethane applications such as surfactants and oil demulsifiers.

EXPERIMENTALInstrumentation

Agilent 1260 Infinity II Isocratic pump (G7110B)Agilent 1260 Infinity II Vial sampler (G7129A)Agilent 1260 Infinity II MCT (G7116A)Agilent 1260 Infinity GPC/SEC Multi-Detector Suite (G7800A) Equipped withMDS Viscometer Detector MDS Light Scattering Detector MDS Refractive Index Detector

Figure 1. Formation of polyther polyols

Method for Analysis

Instrument/Detector/Column CalibrationInstrument and column calibration is performed using EasiVial polystyrene standards. Standards chromatograms are shown overlaid in Figure 2. Calibration data points are shown in Figure 3

Figure 2: Easivial Polystyrene Calibration

RT PS Mp10.2 5115010.6 2915011.0 1954011.6 997011.9 677012.2 443012.6 293013.0 193013.5 102013.9 57514.2 38015.0 162

3

SAMPLE ANALYSIS

Figure 4: Polyol Sample 1

Figure 3: Calibration Curve

Three different molecular weight Polyether polyols were analyzed by GPC. Chromatograms are shown in Figures 4-6. System precision and reproducibility were evaluated by replicate injections of a Broad Polystyrene Standard shown in Figure 7.

Figure 5: Polyol Sample 2

Figure 6: Polyol sample 3

Figure 7: Broad Polystyrene

Sample Name Mp Mn Mw PD Bulk IV

Polyols sample _1 814 811 812 1.001 0.03

Polyols sample _2 4508 4393 4460 1.015 0.08

Polyols sample _3 6146 6181 6182 1.0 0.21

RESULTSMolecular weight results by Triple Detection

The column set comprising Two MiniMIX-D, 250 x 4.6 mm columns provides excellent resolution over a linear operating range from 200 to 400,000 g/mol (PS equivalent). Choosing these columns with an ID of 4.6mm allows us to use a much lower flow rate than conventional GPC columns. At 0.3ml/min we benefit from a 60% reduction in solvent consumption whilst retaining manageable run times.

4

In Figure 8 we see the overlaid chromatogram plots of the three Polyester Polyols

The Agilent 1260 Infinity II GPC system equipped with the Infinity MDS allows a user to study the molecular weights of these polyols.

A well characterized broad distribution polymer sample can be used to periodically check the system performance. Calculated molecular weight by triple detection for the Broad polystyrene standard is shown in the table below.

Figure 8: Overlaid Chromatograms of 3 Polyols

SYSTEM REPRODUCIBILITY:

Instrument/Detector/Column Calibration

Sample Name

Theo-retical,

Mw

Experimental Mw calculated through triple

detector

Asym-metry

Agilent Broad

PS standard

291000 296179 1.9

Reproducibility of the Polyol sample analysis is shown by the replicate chromatograms from the 4 detector channels in Figures 9-12.

Precision of 1260 MDS System

Figure 9: Overlay of 5 replicate runs, Rl, five replicates

Figure 10: Overlay of 5 replicate runs, LS 90, five replicates

Figure 11: Overlay of 5 replicate runs, VS, five replicates

Figure 12: Overlay of 5 replicate runs, LS 15, five replicates

5

Samples Mp Mn Mw PD Bulk IVPolyols sample replicate 1 4430 4279 4364 1.02 0.08Polyols sample replicate 2 4402 4284 4338 1.013 0.08Polyols sample replicate 3 4447 4318 4396 1.018 0.08Polyols sample replicate 4 4511 4357 4426 1.016 0.08Polyols sample replicate 5 4508 4393 4460 1.015 0.08

Results of repeat runs for a typical Polyols sample

1260 MDS triple detector is well suited for analysis of polyols samples even at relatively low molecular weight. System molecular weight accuracy can be monitored using a broad polystyrene polymer with known molecular weight. System reproducibility is shown by analysis of replicate injections of one of the Polyol samples.

CONCLUSIONS

Solutions for your analytical businessMarkets & Applications Programswww.solutions-to-win.com

This information is subject to change without notice.© Agilent Technologies, Inc. 2017

Printed in EU, 2017-05-85991-8195EN