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D3368-17 – Standard Test Method Technical Guide
ASTM D3368-17 (Reapproved 2022) covers the standard specification for unfilled, unpigmented FEP resin sheet and film with a thickness less than 3.175 mm (0.125 in.). The standard establishes a classification system based on material performance and intended use, allowing for precise selection using the defined line callout system.
🏗️ Material Classification and Types
The specification defines four types of FEP sheet and film to support a wide range of industrial conditions, from general-purpose electrical insulation to specialized mold release applications. The line callout system uses predefined cells to refer to the specific type, grade, and property requirements.
| 🟦 Type / Grade | 📐 Description | 🎯 Intended Application |
|---|---|---|
| Type I | General purpose sheet and film | Standard electrical insulation and barrier layers |
| Type II, Grade 1 | Cementable film (one side treatable) | Adhesive bonding on a single surface |
| Type II, Grade 2 | Cementable film (two sides treatable) | Multilayer lamination |
| Type III | Special film with high flexural endurance | Extreme thermal cycling and chemical service |
| Type IV | Mold release film | Composite and production release liners |
📏 Key Material Properties and Test Methods
Materials must conform to the referenced test methods for thickness, mechanical, and electrical properties. Conditioning of specimens must be performed in accordance with Practice D618 prior to testing. Recycled materials are permissible provided they meet the requirements of Section 6.2.
| 🟦 Property | ⚡ Test Method | 📌 Specification Guidance |
|---|---|---|
| Thickness | D374/D374M or TAPPI 411 | Full scope applies to materials less than 3.175 mm (0.125 in.) |
| Tensile Properties | D882 (film) / D638 (sheet) | Differentiates behavior of thin sheeting versus thicker sheet |
| Dielectric Breakdown / Strength | D149 | Tested at commercial power frequencies for electrical insulation |
| Density / Specific Gravity | D792 | Verifies material uniformity for the FEP resin |
| Conditioning | D618 | Standard procedure for conditioning plastics prior to testing |
💡 Tip: A “lot” under this standard is defined as one production run or a uniform blend of two or more production runs (Section 3.1.2). The base resin must meet the requirements of Specification D2116 for FEP Molding and Extrusion Materials.
⚠️ Important: This standard does not address all safety concerns. The safety hazard caveat (Scope 1.3) is expressly limited to the test methods portion (Section 14). Establish appropriate safety, health, and environmental practices before use.
❓ Frequently Asked Questions
🔍 How thick can the material be under ASTM D3368?
The specification specifically covers FEP sheet and film materials less than 3.175 mm (0.125 in.) thick.
💡 What are the distinctions between Type I and Type II film?
Type I is general-purpose. Type II is designed for cementability, subdivided into Grade 1 (cementable on one side) and Grade 2 (cementable on both sides).
⚡ Which test method governs dielectric strength testing?
ASTM D149 is the required test method for determining dielectric breakdown voltage and dielectric strength of the solid electrical insulating materials at commercial power frequencies.
📌 Is there an ISO equivalent to ASTM D3368?
No. As stated in Note 1 of the standard, there is no known ISO equivalent to