Characterization of Biomass-Derived Rigid Polyurethane Foam by Pyrolysis GCMS and Thermogravimetric Analysis

Courtney Taylor, Shimadzu Scientific Instruments, Inc. Columbia, Md., USA

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Introduction

Polyurethane foams (PUF), in both structural and non-structural forms, are commonly used throughout the automotive, insulation and housing industries.

These PUFs are primarily derived from petroleum-based products whose price is tied directly to the cost of crude oil. Due to these rising costs, manufacturers are looking for alternatives. Recent advances in the production of PUFs, using less expensive and renewable biomass, makes this material a viable alternative.

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Various biomass feed stocks were investigated to this end, with some being more promising than others. In this investigation we:

Compare a novel biomass-based rigid polyurethane foam (RPUF) against a control sample of commercially available petroleum-based RPUF

Use the complementary techniques of thermogravimetric analysis and pyrolysis GC/MS

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Methodology

This study used a Shimadzu GCMS-QP2010SE coupled with a PY-3030D Double Shot Pyrolizer and a Shimadzu TGA-50 thermogravimetric analyzer to characterize the samples.

All samples for the TGA portion of this study were measured at programmed temperature rates of 2 °C, 5 °C, 10 °C and 20 °C/min. for kinetics analysis.

Sample weights were kept between 2-4 mg.

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Rigid PUF samples were prepared in the lab with various ratios of glycerol and other biomass-related components.

A control sample of commercial manufacture was obtained and used to develop the pyrolysis GCMS method.

This sample was analyzed at various temperatures in the pyrolizer to determine the optimal conditions (see Figure 1).

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GCMS Analytical Conditions

GC Conditions

MS Conditions

Py-3030D Temp 500 °C

Injector Temp 300 °C

Flow Mode Constant Linear Velocity 39 cm/sec

Split Ratio 100:1

Oven Program 30 °C (1 min) → 20 °C/min → 275 °C (12 min)

Column ZB-5HT 30 M X 0.24 mm X 0.25 µm (Phenomenex Inc.)

Interface Temp 280 °C

Source Temp 200 °C

Scan Range 45-500 m/z

Tune type Normal

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Pyrolysis Scan of Commercial PUF

Figure 1

A temperature of 500 °C was found to give the best pyrolysis-GCMS results and was used as the test condition for all samples.

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Figure 2 shows a comparison of the three prepared samples with different glycerol content and the commercial control.

BioPUFs vs. Commercial

Figure 2

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The control shows early eluting peaks as manufacturing blowing agents, followed by DEG and various species related to diisocyanate.

The lab samples show no blowing agents were used, and the DEG peak is replaced by crude glycerine. All samples contain components related to diisocyanate (see Figure 2).

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TGA Kinetics

TGA kinetics analysis was performed by the Ozawa method. The heating rates used were: 2 °C, 5 °C, 10 °C and 20 °C/min.

Sample weights were kept between 2-4 mg and were sliced from a representative cross-section.

All runs used a nitrogen purge at 40 ml/min. As seen in the thermograms, different formulations show slightly different curves and the kinetics analysis was performed on the primary weight loss (see Figures 3-6).

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TGA Kinetics Analysis Commercial PUF

Figure 3

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Kinetics 4 PUF

Figure 4

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Kinetics C4 PUF

Figure 5

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Kinetics 5 PUF

Figure 6

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Conclusion

Pyrolysis GCMS and thermogravimetric analysis can provide useful information regarding various formulations of biomass-derived rigid polyurethane foams.

In this study, some difficulties encountered included relatively busy GCMS chromatograms and less than stable TGA kinetics runs. Further investigations will include a more detailed pyrolysis EGA analysis and better care will be taken regarding sample morphology in TGA runs.

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