ASTM D7394-18(2023) PDF

Overview

ASTM D7394-18(2023) is the international standard practice for the rheological characterization of architectural coatings using three rotational bench viscometers. Developed by ASTM International, this standard outlines how to evaluate the viscosity profile of waterborne architectural coatings at different shear rates-low, mid, and high-using standard benchtop viscometers. The practice enables paint formulators and quality control analysts to predict key coating performance properties without the need for costly research-grade rheometers. By following ASTM D7394-18(2023), organizations gain a reliable and accessible methodology for routine coating and paint viscosity characterization, supporting product development and consistency.

Key Topics

• Rheological Characterization Across Shear Rates: The standard establishes procedures for measuring low-shear viscosity (LSV), mid-shear viscosity (MSV), and high-shear viscosity (HSV), each using a specific style of rotational bench viscometer:

  • Low-Shear Viscosity (LSV): Represents the ability of coatings to suspend pigments and prevent settling or syneresis in storage. Critical for predicting leveling and sag resistance during and after application.
  • Mid-Shear Viscosity (MSV): Denotes coating consistency and resistance to flow during mixing, pouring, and application. Most architectural coatings have target specifications for MSV, often controlled via thickener adjustments.
  • High-Shear Viscosity (HSV): Measures resistance during application by brush or roller, related to brush-drag and rolling resistance. Influential in determining the ease of application, coverage, and film build.

• Test Equipment and Protocols: The practice specifies the use of three commonly available viscometers-cylindrical- or disc-type for LSV, paddle-type for MSV (Krebs Units), and cone/plate-type for HSV. The viscosity measurements are carried out at prescribed speeds and temperatures to maintain consistency and comparability.

• Performance Prediction: Viscosity profiles obtained through this method can be correlated to performance attributes, including suspension ability, leveling, sag resistance, and ease of application. The approach supports meaningful product comparisons, especially when MSV is controlled across all samples.

• Routine Application: The protocol is designed for daily use in laboratory and quality control settings, allowing for fast assessment and adjustment of paint formulations.

Applications

Adopting ASTM D7394-18(2023) provides practical value to a range of stakeholders:

• Paint Formulation and Development: Enables rapid comparison and optimization of formulations by correlating rheological properties to application performance and in-can behavior, such as pigment suspension and syneresis prevention.
• Quality Control (QC): Offers a standardized, repeatable method for monitoring production consistency, ensuring that viscosity specifications for LSV, MSV, and HSV are reliably met.
• Performance Prediction: Helps anticipate end-use performance characteristics, such as leveling, sag resistance, brush-drag, and hiding power, based on viscosity measurements.
• Cost-Effective Testing: Eliminates the need for expensive laboratory rheometers by leveraging accessible bench viscometers for key viscosity assessments.
• Broader Compatibility: While focused on waterborne architectural coatings, the principles and methods in this standard are suitable for other aqueous and non-aqueous coatings with proper correlation adjustments.

Related Standards

For a comprehensive approach to paint and coating testing, the following ASTM standards are often used alongside ASTM D7394-18(2023):

• ASTM D562 – Consistency of Paints Measuring Krebs Unit (KU) Viscosity
• ASTM D2196 – Rheological Properties of Non-Newtonian Materials by Rotational Viscometer
• ASTM D4287 – High-Shear Viscosity Using Cone/Plate Viscometer
• ASTM D4414 – Measurement of Wet Film Thickness by Notch Gages
• ASTM D4062 – Leveling of Paints by Draw-Down Method
• ASTM D4400 – Sag Resistance of Paints Using a Multinotch Applicator
• ASTM D1005 – Measurement of Dry-Film Thickness of Organic Coatings Using Micrometers

By implementing ASTM D7394-18(2023) in conjunction with these methods, laboratories and manufacturers can optimize both the quality and performance of architectural coatings, ensuring compliance with international testing and quality standards.

Keywords: ASTM D7394-18, rheological characterization, architectural coatings, bench viscometer, paint viscosity, low-shear viscosity, mid-shear viscosity, high-shear viscosity, paint quality control, coating standards.