Abstract
This practice covers infrared spectrophotometry procedures for determining the molecular structural features such as types and number of branches in polyolefins and polyolefin copolymers. The structural features expressed by these determinations affect the ultimate polymeric properties and are useful in showing correlations with many performance properties. The apparatus is comprised of double beam or Fourier transform infrared spectrophotometer, hot plate, microscope slides, compression molding press, metal plates, brass shims, micrometer, and film mounts. Materials shall include polyethylene terephthalate, aluminum, or matte finished teflon-fiberglass sheet. The concentration shall be calculated using either the Beer-Lambert law with the appropriate molar absorptivity or an appropriate calibration curve.
This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.
1. Scope
1.1 This practice covers infrared procedures for determining the molecular structural features in polyolefins and polyolefin copolymers. The structural features of primary concern are the types and numbers of branches. Although this practice centers its attention on polyolefins and polyolefin copolymers, the techniques, with proper modification, can be used for some other polymers as well.
Note 1—
Quantitative determinations require either an internal or an external evaluation of sample thickness. ASTM test methods available for specific features are listed in Tables 1 and 2. TABLE 1 Polyolefin Structural Features Determined by FT-IR
| Structure | Absorption Band, cm–1 | ASTM Test Method |
| Methyl group (polyethylene) | 1378 | D2238 |
| Methyl group (eth-prop copol) | 1380 | |
| Pendant methyl | 935 | |
| Terminal vinyl | 908 | D6248 |
| Trans-vinylene | 965 | D6248 |
| Vinylidene | 888 | D3124 |
TABLE 2 Structural Features in Polyolefin Copolymer Determined by FT-IR
| Structure | Absorption Band, cm–1 | ASTM Test Method |
| Vinyl acetate | 609 | D5594 |
| | 1020 | D5594 |
| | 3270 | D5594 |
| Styrene | 770–700 | |
| | 1600–1500 | |
| Ethyl acrylate | 1640–1730 | |
| | 862 | D3594 |
| Ethylene acrylate | 1280–1200 | |
| | 1640–1625 | |
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of the regulatory limitations prior to use.
Note 2—
There is no known ISO equivalent to this standard.
2. Referenced Documents (purchase separately) 
The documents listed below are referenced within the subject standard but are not provided as part of the standard.
ASTM Standards
D883 Terminology Relating to Plastics
D1505 Test Method for Density of Plastics by the Density-Gradient Technique
D1600 Terminology for Abbreviated Terms Relating to Plastics
D2238 Test Methods for Absorbance of Polyethylene Due to Methyl Groups at 1378 cm-1
D3124 Test Method for Vinylidene Unsaturation in Polyethylene by Infrared Spectrophotometry
D3594 Test Method for Copolymerized Ethyl Acrylate In Ethylene-Ethyl Acrylate Copolymers
D5594 Test Method for Determination of the Vinyl Acetate Content of Ethylene-Vinyl Acetate (EVA) Copolymers by Fourier Transform Infrared Spectroscopy (FT-IR)
D6248 Test Method for Vinyl and Trans Unsaturation in Polyethylene by Infrared Spectrophotometry
E131 Terminology Relating to Molecular Spectroscopy
E168 Practices for General Techniques of Infrared Quantitative Analysis
E932 Practice for Describing and Measuring Performance of Dispersive Infrared Spectrometers
E1421 Practice for Describing and Measuring Performance of Fourier Transform Mid-Infrared (FT-MIR) Spectrometers: Level Zero and Level One Tests
IEEE/ASTM SI-10 Standard for Use of the International System of Units (SI): The Modern System
Keywords
copolymers; FT-IR; infrared spectrophotometry; polyethylene; structural features;
ICS Code
ICS Number Code 83.080.20 (Thermoplastic materials)
DOI: 10.1520/D5576-00R13
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Citing ASTM Standards
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