ASTM E202 Analysis Testing for Ethylene & Propylene Glycols
To measure certain chemical and physical properties of ethylene glycols and propylene glycols ASTM E202 is used and it can be used to determine compliance with specifications in which limits are established for these properties.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
Overview
ASTM E202 provides standard test methods for the chemical analysis of ethylene glycols and propylene glycols, including monoethylene glycol (MEG), diethylene glycol (DEG), triethylene glycol (TEG), and their propylene glycol counterparts. The methods cover the determination of purity, water content, distillation range, acidity, and specific gravity.
These tests are essential for glycol producers, formulators, and users in antifreeze, polymer, solvent, and pharmaceutical applications who must verify raw material purity and compliance with ASTM product specification standards.
Scope, Applications, and Benefits
Scope
ASTM E202 evaluates:
- Purity and assay of mono-, di-, and tri-ethylene/propylene glycols
- Water content (Karl Fischer)
- Distillation range
- Acidity (as acetic acid)
- Specific gravity and refractive index
- Color (APHA/Pt-Co scale)
Applications
- Antifreeze and engine coolant raw material QC
- Polyester (PET, PBT) and polyurethane resin feedstock verification
- Solvent and plasticizer grade glycol analysis
- Pharmaceutical-grade glycol purity verification
- Heat transfer fluid composition analysis
Benefits
- Comprehensive purity characterization in a single standard
- Detects cross-contamination between glycol grades (MEG vs. DEG)
- Supports product release and incoming material inspection
- Enables compliance with ASTM D3306 coolant and resin grade specs
- Provides traceable analytical data for customer certification
Test Process
Sample Preparation
Glycol samples are received, logged, and aliquoted for each test method; samples are handled in sealed vessels to prevent moisture absorption from the atmosphere.
1Physical Property Testing
Specific gravity (D891), refractive index (D1218), and color (D1209 Pt-Co) are measured on fresh sample aliquots at 20 °C using calibrated instruments.
2Chemical Analysis
Water content (Karl Fischer, D1123), acidity (D1613), and distillation range (D1078) are determined using the appropriate methods cited in ASTM E202.
3Purity Calculation & Reporting
All measured values are compiled; glycol purity (%) is calculated by difference or by GC assay; results are compared to specification limits and a CoA is issued.
4Technical Specifications
| Parameter | Details |
|---|---|
| Applicable Materials | MEG, DEG, TEG, MPG, DPG (glycol grades) |
| Water Content Method | Karl Fischer titration (D1123) |
| Acidity Method | Potentiometric titration (D1613) |
| Distillation Method | ASTM D1078 |
| Color Scale | APHA/Pt-Co (D1209) |
Instrumentation Used for Testing
- Karl Fischer titrator (volumetric/coulometric)
- Potentiometric titrator (acidity)
- Automatic distillation apparatus (D1078)
- Refractometer (Abbe type)
- Digital density/specific gravity meter
- Colorimeter (Pt-Co/APHA)
Results and Deliverables
- Assay/purity (wt%) of the glycol
- Water content (ppm or wt%)
- Acidity (mg KOH/g or ppm as acetic acid)
- Distillation range (initial boiling point, dry point)
- Specific gravity and refractive index
- Color (APHA/Pt-Co units)
- Report of analysis per ASTM E202
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Frequently Asked Questions
MEG and DEG have different physical properties and end-use applications. Cross-contamination of DEG into MEG in antifreeze or PET resin feedstock can reduce freeze protection efficiency and adversely affect polymer molecular weight and mechanical properties. ASTM E202 GC methods can quantify both in a mixture.
Water dilutes the glycol, reducing its effective concentration and depressing freeze and boiling protection performance. For polyester resin applications, water initiates unwanted hydrolysis reactions during polymerization, reducing molecular weight. Even small amounts (>0.05 wt%) are tightly controlled.
Acidity is measured by potentiometric titration and expressed as mg KOH/g or ppm as acetic acid. Acidic glycols indicate oxidative degradation and accelerate corrosion of metals in cooling systems and process equipment, making acidity a key quality parameter.
Yes, with modifications for degradation by-products, colored solutions, and elevated contamination levels. Used glycol analysis typically supplements ASTM E202 physical/chemical tests with additional tests for inhibitor depletion, corrosion metals (ICP-OES), and degradation acids.
Pharmaceutical-grade MPG (USP) must meet higher purity standards (>99.5% assay), tighter limits on aldehydes, heavy metals, and water, and must be manufactured under GMP conditions. Industrial-grade MPG meets ASTM specifications adequate for antifreeze, solvent, and non-food applications but lacks the USP purity controls.
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