Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5940-96 – Standard Test Method Technical Guide
🧪 Mold Design and Specimen Geometry
This practice, ASTM D5940-96, defines the standard procedures for preparing small plate test specimens of thermoplastics using Type D ISO molds. The two-cavity molds are designed to produce 60 mm by 60 mm plates, available in two specific thicknesses as defined by the mold type. This standard is technically identical to ISO 294-3.
The molds can be adapted with inserts for the specific purpose of studying weld line behavior, a common factor in injection molded part strength, as detailed in Annex A2.
| 🟦 Property | 📏 Type D1 (Thin Plate) | 📐 Type D2 (Standard Plate) |
|---|---|---|
| Plate Length (mm) | 60 – 62 | 60 – 62 |
| Plate Width (mm) | 60 – 62 | 60 – 62 |
| Plate Thickness (mm) | 1.0 – 1.1 | 2.0 – 2.1 |
| Primary Applications | Specific multi-axial impact or optical evaluations | General mechanical, impact, and shrinkage testing |
⚙️ Technical Requirements and Measurement Features
The construction of the Type D mold must comply with the general principles outlined in ASTM D 5939, Section 4.1, with specific dimensions adapted for the plate geometry. A critical requirement is the integration of a pressure sensor (P) within the mold cavity, as depicted in Figure 2 of the standard.
⚡ Critical Note on Gate Design: The standard explicitly warns that gates with strongly reduced thickness have a great influence on the orientation of the material within the plate up to large distances from the gate. Therefore, the thickness step at the gate has been chosen at a minimum value to facilitate measuring the molding shrinkage mechanically; see ISO 294-4.
The pressure sensor is mandatory when the mold is used for determining molding shrinkage according to ISO 294-4. It is also recommended for general control of the injection period. The sensor must be perfectly coplanar with the mold cavity surface to avoid disturbing the polymer flow during the injection phase.
| 📌 Feature | 🎯 Specification / Reference |
|---|---|
| Mold Cavities | Two (Type D) |
| Primary Geometry | Plate, 60 mm × 60 mm |
| Related Construction Standard | ASTM D 5939 (Section 4.1) |
| Shrinkage Measurement | Per ISO 294-4 (requires pressure sensor P) |
| Impact Testing Protocol | Per ISO 6603 (Falling Dart / Instrumented Puncture) |
🌐 Scope and Interoperability with Standards
This practice serves as a critical foundation for generating consistent plate specimens used across a wide array of mechanical and thermal characterization tests. By strictly adhering to the mold specifications and processing conditions, laboratories can achieve highly comparable and reproducible data.
The small plates produced are specifically cited for use in determining multi-axial impact behavior (ISO 6603-1 and ISO 6603-2) and molding shrinkage (ISO 294-4). The general principles of injection molding test specimens from thermoplastics are covered by ISO 294-1. Furthermore, it supports the acquisition of comparable single-point data in accordance with ASTM D 5935.
✅ Compliance and Equivalence: This practice (D 5940) is strictly identical to ISO 294-3. Users familiar with the ISO system can directly apply this standard without any deviation in mold design or procedural steps, ensuring seamless international data acceptance.
❓ Frequently Asked Questions
🔍 What is the exact difference between Type D1 and Type D2 molds?
The core difference is the molded plate thickness. Type D1 produces a plate with a thickness of 1.0 to 1.1 mm, while Type D2 produces a plate with a thickness of 2.0 to 2.1 mm. Both molds produce the standard 60 mm by 60 mm plate footprint.
© 2026 TNLab — This article is a technical interpretation for reference only. The original standard as published by ASTM International takes precedence.