ASTM D6953 Standard Test Method for Determining Primary and Secondary Antioxidants and Erucamide Slip Additives in Polyethylene Plastics Using Liquid Chromatography (LC)
What is ASTM D6953?
ASTM D6953 is a standard test method for determining primary and secondary antioxidants and erucamide slip additives in polyethylene plastics by liquid chromatography. This method applies to polyethylene resins, where additives are extracted with isopropanol or cyclohexane (depending on resin density), separated by liquid chromatography, and detected by ultraviolet absorbance. The test determines additive concentration in SI units, providing useful information for evaluating polyethylene composition and additive levels. Manufacturers, researchers, and engineers use this test to assess additive levels and determine polyethylene resin properties to ensure material consistency.
Get Certified ASTM D6953 Testing for Reliable Polyethylene Quality
Certified testing analyzes selected antioxidants and erucamide slip additives in polyethylene using liquid chromatography. By verifying additive concentrations, manufacturers ensure that their polyethylene formulations meet established quality requirements. In addition, through careful extraction and chromatographic measurement, laboratories obtain data to evaluate additive levels and investigate batch-to-batch differences.
What is the Scope of ASTM D6953?
ASTM D6953 is a standard test method that describes the essential aspects and considerations for testing selected additives in polyethylene materials. It defines the material range, measurement approach, reporting basis, and practical factors laboratories should consider when performing the test. These factors help technicians understand the method’s purpose and how to use the results to evaluate materials and make quality control decisions.
Material type: Polyethylene plastics containing primary or secondary antioxidants and slip additives.
Purpose: Determination of the selected antioxidant and slip-additive content in polyethylene materials.
Properties evaluated: The concentration of specified polymer additives that include antioxidants and erucamide slip additives.
Testing Method: Extract the additives from polyethylene using isopropanol for resin densities below 0.94 g/cm³ or cyclohexane for resin densities above 0.94 g/cm³. The extract is subjected to separation by liquid chromatography techniques, and UV absorbance provides the basis for quantitation by means of external calibration.
Result: The method determines quantitative additive results; the standard specifies SI units as the standard units of measurement. Under optimum conditions, the lowest detection level for an antioxidant is about 2 ppm.
Test limitations: Interferences may occur from substances that elute close to the target additive, impurities in the solvents, and changes introduced during sample grinding. This standard notes that some erucamide can be lost during grinding, and excessive grinding may degrade antioxidants.
Methodology: The extraction solvent depends on polyethylene resin density, with 0.94 g/cm³ as the dividing value. The method also requires attention to sample preparation because grinding conditions can influence additive recovery.
Applications: The results can be used for polyethylene quality control, additive-level monitoring, material comparison, formulation evaluation, and investigating differences in polymer composition and performance.
What are the Uses of ASTM D6953 Testing?
ASTM D6953 provides quantitative information about selected antioxidants and erucamide slip additives in polyethylene. The standard method:
Quantifies selected antioxidant and erucamide slip-additive concentrations in polyethylene.
Facilitates compositional verification of additives used in polyethylene materials.
Enables comparison of additive levels between different polyethylene samples or formulations.
Provides information for investigating the stabilizer composition of polyethylene resins.
Evaluates variations in additive content that may be associated with differences in polymer performance.
Assists in identifying changes in additive composition between polyethylene materials or production batches.
Why is ASTM D6953 Important?
ASTM D6953 links the chemical makeup of selected additives to the behavior of polyethylene materials. The additives in polyethylene can affect polymer processing. Therefore, understanding the composition of additives incorporated into polyethylene can provide insight into factors that may drive changes in the material’s performance. Investigating the amount of stabilizers present in the material helps identify if variations in polyethylene materials are connected to their additive system. This data helps troubleshoot issues related to unexpected changes in material behavior and understand differences between polyethylene materials.
ASTM D6953 Equipment and Sample Preparation Guide
ASTM D6953 specifies controlled sample handling and the required equipment to prepare an extract suitable for liquid chromatographic analysis. In addition, the test method reduces the polyethylene sample to a suitable size, extracts the additives, and prepares them for chromatographic measurement.
Technicians select a representative polyethylene resin containing the primary or secondary antioxidants and slip additives covered by ASTM D6953.
Sample preparation
Technicians grind the polyethylene sample using a suitable mill and weigh approximately 5 g of the prepared material for extraction. Technicians use isopropanol for resin densities below 0.94 g/cm³ and cyclohexane for resin densities above 0.94 g/cm³.
Sample dimensions
Technicians grind polyethylene with a density below 0.94 g/cm³ to about 1 mm (20 mesh), whereas material above 0.94 g/cm³ is reduced to about 0.5 mm (40 mesh). The method therefore uses prepared particles rather than a shaped or dimensioned specimen.
Instrumentation
The method uses a liquid chromatograph fitted with a UV detector, a C-8 or C-18 reverse-phase column and a data acquisition system. Sample preparation also requires a suitable grinding mill, reflux extraction, an analytical balance, and a 0.22-μm PTFE filtration system.
ASTM D6953 Testing Procedure And Requirements
ASTM D6953 consists of preparing a polyethylene extract under controlled conditions and introducing it into the liquid chromatograph. The process then moves to sample grinding, solvent extraction, filtration, chromatographic separation, and quantitative evaluation of selected additives. ASTM D6953 testing procedure is as follows:
Technicians grind the polyethylene sample to pass about 1 mm (20 mesh) for resin densities below 0.94 g/cm³ or about 0.5 mm (40 mesh) for densities above 0.94 g/cm³. Minimize grinding time to avoid additive degradation or loss.
Additive Extraction
Technicians weigh about 5 g of the sample into a 125 mL flask with boiling chips and add about 50.0 mL of the selected solvent. Then, reflux the mixture for at least 2 h using isopropanol for densities below 0.94 g/cm³ and cyclohexane for densities above 0.94 g/cm³.
Extract Filtration
After extraction and cooling, the technician transfers about 4 mL of the solvent extract using a syringe equipped with a 0.22-μm PTFE filter into a sample vial.
Liquid Chromatographic Analysis
The technician introduces the extracted solution into the liquid chromatograph under the specified chromatographic conditions. Furthermore, technicians use a C-8 or C-18 reverse-phase column and monitor the extracted solution with UV detection.
Quantitative Evaluation
Analysts compare the chromatographic response with external calibration data prepared from the relevant additive standards. Analysts calculate the applicable additive concentration from the measured response.
Result Reporting
The final results report the concentrations of the applicable antioxidants and erucamide slip additive determined from the chromatographic analysis.
ASTM D6953 Testing Process and Data Collection
Technicians prepare the polyethylene extract, load the liquid chromatography column, and separate the additives, which the device then detects. The reverse-phase column isolates the substance, and the detector records the response as the mixture leaves the column. Technicians then use chromatographic peaks to estimate the concentrations of the selected antioxidants and the erucamide slip additive by comparing the results to preparations with known concentrations. Moreover, UV detection is used to determine suitable compounds in the mixture, whereas Erucamide slip requires special consideration because it does not have a UV absorption maximum in the range. In addition, technicians ensure they follow the instructions during chromatographic analysis so the collected peaks can be used for accurate calculations.
Polyethylene resin tested by liquid chromatography to determine antioxidant and erucamide levels according to ASTM D6953.
Common Challenges and Troubleshooting in ASTM D6953
Common problems during ASTM D6953 analysis include additive loss due to grinding, improper extraction, solvent contamination, and co-elution of interfering compounds. Overall, these issues may impact the recovery of additives and, consequently, the accuracy of test results. Therefore, technicians ensure that additives undergo prolonged grinding, use a suitable solvent, and filter the extract. Moreover, optimizing extraction and chromatography parameters can also improve results. Therefore, proper sample preparation, selecting an appropriate solvent, and maintaining equipment are essential aspects of ASTM D6953 testing.
ASTM D6953 Analysis, Results and Interpretation
The chromatogram obtained from ASTM D6953 provides the basis for evaluating the additive content in the polyethylene extract. In addition, peak identification and measurement allow technicians to quantify the target additives and to assess their concentration in the polyethylene sample. The main points of interpretation are:
What type of polyethylene additives can be analyzed by ASTM D6953?
ASTM D6953 covers selected primary and secondary antioxidants and erucamide slip additives used in polyethylene.
How is the extraction solvent selected in ASTM D6953?
Isopropanol is used for polyethylene resins with a density below 0.94 g/cm³, while cyclohexane is used for those above 0.94 g/cm³.
What is the importance of the grinding process in ASTM D6953?
To increase the surface area of the sample that is exposed to the extraction solvent.
How are additive concentrations determined in ASTM D6953?
Additive concentrations are determined by comparing the response of the separated additives to their corresponding external calibration standards using chromatography.
Laraib Hashmi is an aspiring research enthusiast and science content professional with a strong interdisciplinary skill set, holding a postgraduate degree in Applied Microbiology from KIIT Bhubaneshwar, Odisha. Know More
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