Determination of percent glycerol monostearate in polypropylene by infrared spectroscopy
Applications | 2012 | Agilent TechnologiesInstrumentation
The accurate quantification of glycerol monostearate (GMS) in polypropylene is essential for ensuring consistent antistatic performance and product quality in polymer manufacturing. Infrared spectroscopy offers a rapid, non-destructive approach well suited to process control when additive packages are defined and interferences are managed.
This work presents a validated FTIR-based method to determine GMS content in polypropylene over the range 0.05–0.8 wt%. It addresses sample preparation, spectral measurement, calibration development and interference correction for ester-based antioxidants.
Samples of polypropylene resin are molded into 0.4–0.7 mm films using a hydraulic press at 200 °C. FTIR spectra are acquired at ≥4 cm⁻¹ resolution and 74 scans. The ester carbonyl absorption of GMS at 1739 cm⁻¹ is normalized to the polypropylene reference band at 1044 cm⁻¹. The resulting absorbance ratio is applied to a linear Beer’s Law calibration.
A calibration curve (Wt% GMS = 1.761 × (A₁₇₃₉/A₁₀₄₄) + 0.145) exhibited linearity across the target range. Surface residues can cause non-linearities, remedied by a dry lint-free wipe. Certain antioxidants (e.g., Irganox® 1010, 3114) absorb near the GMS band and require a correction factor when present.
This FTIR method provides rapid, reproducible measurements ideal for in-line or at-line process control. The simple film mounting with DialPath or TumblIR and method-driven software automates calculations, reducing operator variability.
Advances may include integration with real-time monitoring systems, broader additive libraries for automated interference corrections and adaptation to filled or pigmented resins using multivariate spectral analysis.
The described FTIR procedure enables accurate quantification of GMS in polypropylene with minimal sample preparation. Its ease of use and robust calibration make it a valuable tool for polymer additive monitoring.
FTIR Spectroscopy
IndustriesEnergy & Chemicals
ManufacturerAgilent Technologies
Summary
Importance of the topic
The accurate quantification of glycerol monostearate (GMS) in polypropylene is essential for ensuring consistent antistatic performance and product quality in polymer manufacturing. Infrared spectroscopy offers a rapid, non-destructive approach well suited to process control when additive packages are defined and interferences are managed.
Objectives and Study Overview
This work presents a validated FTIR-based method to determine GMS content in polypropylene over the range 0.05–0.8 wt%. It addresses sample preparation, spectral measurement, calibration development and interference correction for ester-based antioxidants.
Methodology
Samples of polypropylene resin are molded into 0.4–0.7 mm films using a hydraulic press at 200 °C. FTIR spectra are acquired at ≥4 cm⁻¹ resolution and 74 scans. The ester carbonyl absorption of GMS at 1739 cm⁻¹ is normalized to the polypropylene reference band at 1044 cm⁻¹. The resulting absorbance ratio is applied to a linear Beer’s Law calibration.
Instrumentation Used
- Agilent Cary 630 FTIR spectrometer with DialPath or TumblIR accessory (1000 µm path length)
- Alternative portable FTIR (Agilent 5500/4500 Series) capable of similar resolution
- Hydraulic press with heated platens (200 °C, ≥25 000 lb force)
- Optional chase mold and aluminum sheets (0.05–0.18 mm)
Main Results and Discussion
A calibration curve (Wt% GMS = 1.761 × (A₁₇₃₉/A₁₀₄₄) + 0.145) exhibited linearity across the target range. Surface residues can cause non-linearities, remedied by a dry lint-free wipe. Certain antioxidants (e.g., Irganox® 1010, 3114) absorb near the GMS band and require a correction factor when present.
Benefits and Practical Applications
This FTIR method provides rapid, reproducible measurements ideal for in-line or at-line process control. The simple film mounting with DialPath or TumblIR and method-driven software automates calculations, reducing operator variability.
Future Trends and Potential Applications
Advances may include integration with real-time monitoring systems, broader additive libraries for automated interference corrections and adaptation to filled or pigmented resins using multivariate spectral analysis.
Conclusion
The described FTIR procedure enables accurate quantification of GMS in polypropylene with minimal sample preparation. Its ease of use and robust calibration make it a valuable tool for polymer additive monitoring.
References
- Collins W., Seelenbinder J., Higgins F. Determination of Percent Glycerol Monostearate in Polypropylene by Infrared Spectroscopy; Agilent Technologies Application Note 5991-0467EN, May 2012.
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