Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D5327-97 – Standard Test Method Technical Guide
📐 Scope and Terminology
ASTM D5327-97 (Reapproved 2021) establishes a standardized laboratory practice for evaluating and comparing the transfer efficiency (TE) of spray-applied coatings. Transfer efficiency is strictly defined as the ratio of paint solids deposited on a target to the total paint solids used during the application process, expressed as a percentage. This practice is specifically designed to isolate the effect of changing operating variables or paint formulations under controlled conditions. The standard is derived from Test Method D5009 and was originally developed in conjunction with a study for the U.S. Environmental Protection Agency.
⚠️ Critical Limitation on Extrapolation: The standard explicitly states that this laboratory practice indicates only the direction of the effect of operating variables on transfer efficiency. The magnitude of the effect can be determined only with specific plant experience. The standard makes it clear that it is not possible to extrapolate laboratory results to production conditions due to the nature of the critical parameters involved.
Key terminology defined for the practice includes:
- Fluid Mass Flow Rate (g/min): The mass flow rate of paint during the test.
- Mass of Foil (g): The weight of each target foil before being painted.
- Mass of Foil Plus Paint Solids (g): The weight of each target foil plus the deposited paint solids after solvent evaporation.
⚙️ Test Procedure and Critical Parameters
The reproducibility of this practice is highly dependent on the degree of control of the parameters listed in Section 8 of the standard. It is imperative that all process or formulation parameters, except the specific variable being studied, be kept strictly consistent from test to test to ensure valid comparative results. The practice relies on several standardized ASTM methods for the accurate characterization of the coating materials.
| 🟦 Designation | 📏 Title | 📐 Role in TE Testing |
|---|---|---|
| D1200 | Test Method for Viscosity by Ford Viscosity Cup | Establishes paint viscosity prior to application. |
| D2369 | Test Method for Volatile Content of Coatings | Determines the exact solids (non-volatile) content for calculating TE. |
| D3925 | Practice for Sampling Liquid Paints and Related Pigmented Coatings | Ensures representative samples are obtained for testing. |
| D5009 | Evaluating and Comparing Transfer Efficiency (Lab Conditions) | Alternative method with conveyor and mass flow equipment for higher reproducibility. |
💡 Best Practice for Variable Control: To maintain the integrity of the comparative study, parameters such as fluid mass flow rate, atomization air pressure, spray distance, fan pattern, and applicator technique must be rigorously controlled. The standard warns that if these are not kept consistent, the results of the study are to be questioned.
Safety compliance is mandatory. Users must establish appropriate safety, health, and environmental practices. The standard specifically references NFPA 33 (Spray Application Using Flammable and Combustible Materials) and NFPA 86 (Standard for Ovens and Furnaces), with specific hazard statements located in Sections 7, 8.10.10.5, and 8.13.1.
📊 Key Measured Properties and Calculations
The primary output of the practice is the Transfer Efficiency value. The fundamental measured data points are the mass of paint solids deposited on the target foils (derived from the mass of foil plus paint solids minus the mass of foil) and the total mass of paint solids used (calculated from the fluid mass flow rate, spray time, and paint solids content).
Calculation of Transfer Efficiency:
TE (%) = (Mass of Paint Solids Deposited / Total Mass of Paint Solids Used) × 100%
All values are to be reported in SI units, which are regarded as the standard for the practice.
❓ Frequently Asked Questions
🔍 How does this practice (D5327) differ from Test Method D5009?
D5327 is designed for general laboratory spray equipment without a conveyor. D5009 defines a method that utilizes a conveyor and mass flow measurement equipment. The standard notes D5009 is a “suitable, potentially more reproducible, tested method” for laboratories that have access to such equipment.
💡 What are the key variables that must be controlled for valid results?
The standard lists these in Section 8.13. The most critical requirement is that all parameters except the one intentionally being changed must remain consistent. Key variables include paint viscosity (per D1200), fluid mass flow rate, atomization parameters, spray distance, and target type.
⚡ Why can’t laboratory TE results be directly extrapolated to the plant floor?
According to Section 1.3, while the test indicates the direction of the effect of a variable on TE, the magnitude of that effect can only be determined with specific plant experience. The interaction of complex parameters in a production environment prevents direct extrapolation of laboratory data.
📌 What units are required for reporting results?
The values stated in SI units are to be regarded as the standard. Values given in parentheses are for information only. Fluid mass flow rate, for example, is measured in grams per minute.