ASTM D 2238 – Polyethylene Absorbance Analysis

The 1378.4-cm-1 (7.255-m) infrared absorption band associated with the methyl groups in the material is specifically targeted for measurement by ASTM D 2238 Standard Test Methods T, which is intended for the quantitative analysis of polyethene. To properly measure the presence and concentration of methyl groups in polyethene samples, this analytical method uses infrared spectrophotometry.

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ASTM D 2238 – Polyethylene Absorbance Analysis

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM D2238 determines the absorbance characteristics of polyethylene materials using infrared spectroscopy. The test evaluates molecular structure, oxidation level, and the presence of functional groups that influence material performance.

This method is widely used in polymer manufacturing and quality control. It helps assess material composition, degradation, and consistency for applications in packaging, cables, and industrial products.

Scope, Applications, and Benefits

Scope

ASTM D2238 evaluates polyethylene by measuring infrared absorbance at specific wavelengths. The test provides insight into chemical structure and oxidation behavior.

The test evaluates:

Infrared absorbance characteristics of polyethylene
Presence of oxidation or degradation products
Molecular structure and functional groups
Material consistency and uniformity
Suitability for processing and applications

Applications

Polyethylene films and sheets
Wire and cable insulation materials
Packaging and industrial plastics
Polymer research and development
Quality control in PE production
Material degradation studies

Benefits

Provides detailed chemical characterization
Detects oxidation and material degradation
Supports material quality and consistency
Assists in formulation and process control
Enables comparison of polyethylene grades

Test Process

Sample Preparation

Polyethylene samples are prepared as thin films or pellets.

Instrument Setup

Samples are placed in an infrared spectrometer.

Spectral Measurement

IR radiation is passed through the sample to measure absorbance.

Data Recording & Evaluation

Absorbance peaks are analyzed to determine material properties.

Technical Specifications

Parameter	Details
Applicable Materials	Polyethylene (PE)
Measurement Method	FTIR spectroscopy
Wavelength Range	~4000 cm⁻¹ to 400 cm⁻¹
Sample Thickness	~0.01 mm to 1 mm
Measurement Accuracy	±1%
Measured Outputs	Absorbance spectrum, oxidation indices

Instrumentation Used for Testing

FTIR spectrometer
Sample holder or film preparation tools
Calibration standards
Optical measurement system
Data acquisition software
Sample preparation equipment

Results and Deliverables

Infrared absorbance spectrum
Oxidation and degradation analysis
Chemical structure evaluation
Comparative material assessment
Test condition summary
ASTM compliance report

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Frequently Asked Questions

ASTM D2238 measures infrared absorbance of polyethylene materials. It evaluates chemical structure and presence of functional groups, helping assess material composition, oxidation levels, and quality consistency in polyethylene products.

Key parameters include wavelength range, sample thickness, instrument calibration, and baseline correction. Proper sample preparation ensures accurate infrared absorbance measurement and reliable analysis.

The test measures absorbance peaks corresponding to specific chemical bonds. Results indicate presence of oxidation, additives, or structural variations in polyethylene materials.

ASTM D2238 applies to polyethylene materials such as films, sheets, and molded products used in packaging, construction, and industrial applications.

ASTM D2238 depends on proper sample preparation and instrument calibration. Overlapping peaks or impurities may affect interpretation, and additional analytical methods may be required for detailed chemical characterization.