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D3981-09 – Standard Test Method Technical Guide
📐 Scope and Material Classification
Standard D3981-09a (Reapproved 2024) covers unpigmented, unsupported, sheet or tubular medium-density polyethylene (MDPE) films. The resins must have densities in the range from 926.0 to 938.0 kg/m³ (0.926 to 0.938 g/cm³), measured on molded plaques. The standard applies broadly to homopolymers, copolymers (including low-pressure PE and EVA), and blends thereof. It also permits the incorporation of recycled polyethylene film or resin as feedstock, subject to meeting the full requirements of the standard and any specific agreements between the producer and end user (see Note 1 of the standard regarding Guide D7209).
The standard explicitly does not cover oriented heat-shrinkable films. Special care is required when applying the specification to colored or pigmented films, as the standard does not address specific problems associated with coloring, such as pigment dispersion and density changes.
📊 Dimensional and Density Specifications
| 🔬 Property | 📏 Specification Range | 📝 Notes |
|---|---|---|
| Density (Molded Plaque) | 926.0 – 938.0 kg/m³ (0.926 – 0.938 g/cm³) | Measured on compression molded plaques |
| Film Thickness | 25 – 100 µm (0.001 – 0.004 in.) | Inclusive thickness range |
| Maximum Width | 3.05 m (120 in.) | Sheet or lay-flat tubular width |
| Material Forms | Unpigmented, Unsupported, Sheet/Tubular | Scope of the specification |
| Polymer Types | Homopolymer, Copolymer, Blends | Includes EVA copolymers and low-pressure PE |
| Recycled Feedstock | Permitted (in whole or in part) | Must meet all specification requirements |
⚠️ Special Care for Pigmented Films: This specification does not address specific problems associated with coloring, such as quantity and quality of pigment dispersion, optical properties, and increase in density. These and other areas must be taken into account by mutual agreement between the supplier and the purchaser.
⚙️ Intrinsic Quality and Physical Property Requirements
The standard defines levels of various physical properties from which specifications for specific films are to be described. The dimensional tolerances included in Sections 7.2 through 7.5 of the standard apply to all films falling within this scope. Key intrinsic quality requirements include density, workmanship, impact strength, tensile strength, heat sealability, and odor. Additionally, classification properties such as stiffness, coefficient of friction, optical properties, and surface treatment are covered. The required performance levels for a given application are selected from Section 6 and the corresponding tables of the standard.
| 🎯 Quality / Property | 📋 Category | 📌 Details |
|---|---|---|
| Density | Intrinsic Quality | Must be 926.0 – 938.0 kg/m³ |
| Workmanship | Intrinsic Quality | Film must be free of visual defects |
| Impact Strength | Intrinsic Quality | Critical for packaging durability |
| Tensile Strength | Intrinsic Quality | Measured in machine and transverse directions |
| Heat Sealability | Intrinsic Quality | Essential for bag and pouch fabrication |
| Odor | Intrinsic Quality | Must be acceptable per standard requirements |
| Stiffness / COF / Optics | Classification Properties | Selected per Section 6 for the specific application |
💡 SI Units as Standard: The values stated in SI units (e.g., kg/m³, µm, m) are to be regarded as the standard for this specification. The values in parentheses (e.g., g/cm³, in.) are given for information only. Note there is no known ISO equivalent to this standard.
❓ Frequently Asked Questions
🔍 What is the exact density range for Medium-Density Polyethylene films under D3981?
The specification requires densities in the range from 926.0 to 938.0 kg/m³ (0.926 to 0.938 g/cm³), as measured on molded plaques.
💡 Does ASTM D3981 allow the use of recycled polyethylene?
Yes. Section 1.5 explicitly allows for the use of recycled polyethylene film or resin as feedstock, in whole or in part, provided all requirements of the specification are met. Specific requirements may also be governed by the producer and end user.
⚡ What are the dimensional limitations for thickness and width?
The thickness of the films covered ranges from 25 to 100 µm (0.001 to 0.004 in.). The maximum width of the sheet or lay-flat is 3.05 m (120 in.).
📌 Is D3981 applicable to oriented heat-shrinkable films?
No. Section 1.8 of the standard explicitly excludes oriented heat-shrinkable films from the scope of this specification.