ASTM F2029 Standard Practices for Making Laboratory Heat Seals for Determination of Heat Sealability of Flexible Barrier Materials as Measured by Seal Strength

Get Certified to ASTM F2029 for Reliable Heat Seal Performance 

A heat seal layer provides adequate seal strength for the application, but other properties, such as overall construction and thickness, also affect how a material seals. Certified ASTM F2029 heat seal preparation measures the impact of these changes in a consistent, repeatable way. The results help manufacturers select sealing conditions and compare sealing films that are under consideration. A known practice also provides packaging engineers with a reliable starting point prior to full-scale equipment. 

The scope of ASTM F2029 includes: 

• Material type: Flexible barrier materials, such as webs of the same or different materials, either homogeneous, coextruded, coated, or laminated. 
• Purpose: To prepare heat seals in the laboratory and to test the heat seal strength data to assess the heat sealability. 
• Properties measured: Seal strength and heat sealability.  
• Method: Hot-bar and/or impulse sealing in a laboratory sealer. 
• Result: Heat seal curve of the seal strength versus sealing temperature for a given dwell time and pressure. 
• Practice limitations: Not applicable to seal strength measurement (Test Method F88); hot tack (Test Method F1921); seal continuity; or production equipment validation.
• Use conditions: Laboratory sealers are not the same as manufacturing equipment; there are differences in the size of the sealing area, sealing speed, and scale.
• Applications: Creation of initial bonding and sealing conditions for flexible barrier materials. 

What are the Uses of ASTM F2029 Testing?

ASTM F2029 provides a standard method for seal preparation and seal strength measurement for laboratories, while packaging engineers employ the test results to select the appropriate materials and seal conditions. This standard-

• Makes laboratory heat seals at controlled temperature, dwell, and pressure.
• Evaluates how construction and thickness affect heat sealability of the materials.
• Facilitates comparison of sealability of various types of flexible barrier materials.
• Generates a heat seal curve that is used as the basic means of comparing materials.
• Gives a basis for establishing sealing conditions on production equipment.
• Compares the heat sealability, using Test Method F88, with the seal strength. 

What Materials Does ASTM F2029 Cover? 

ASTM F2029 is applicable to flexible barrier materials for forming heat seals. These include one-layer films and various multi-layer webs produced by coextrusion, coating, or lamination. Technicians can seal webs of similar material to each other or dissimilar materials together. Laboratories make a selection of representative web samples to ensure the resulting data reflects the material, not differences in preparation.

Why is ASTM F2029 Important? 

ASTM F2029 specifies controlled procedures for the preparation of heat seals and evaluation of heat seal strength data. The properties of the material itself influence the sealing properties of the material, although a heat seal layer with sufficient seal strength is required for the application. The results help engineers to compare the sealing performance of materials and help decide if a material will meet the sealing requirements in the production process. The heat seal curve and the seal strength data serve as a reference for determining the sealing conditions for the full-scale manufacturing equipment. 

ASTM F2029 Heat Seal Preparation Process and Data Collection 

This process begins with an analyst picking out representative web samples and conditioning them. The technician then makes heat seals at a number of sealing temperatures, leaving the dwell time and pressure fixed. Then the laboratory tests the seal strength of each seal using Test Method F88. Analysts then use the curve of seal strength vs. sealing temperature to determine the strength of the heat seal. 

Common Challenges and Troubleshooting

Ensuring reliable ASTM F2029 results is dependent upon consistent sample conditioning, accurate temperature control, and constant dwell time and pressure. The disparities between a laboratory sealer and production equipment can result in a wide range of variance between lab results and manufacturing performance. The high-temperature section of the heat seal curve may also indicate failure of the substrate, not necessarily failure of the seal. Technicians minimise these problems by keeping all the sealing conditions fixed and changing only the temperature. The engineer also relies on laboratory information as a reference when setting conditions on full-scale equipment. 

• Laboratory reports heat seal strength as the force required to peel the seal apart, per unit width of seal.
• Analysts display the heat seal curve, which shows the seal strength as a function of sealing temperature for a specified dwell time and pressure.
• Technicians record if the specimen fails at the seal or if the specimen fails in the substrate or another layer, as the actual strength of the seal might be slightly higher than the measured strength.
• Engineers take into account that the higher-temperature portion of the curve may be affected by substrate failure and may not accurately represent seal strength.
• Manufacturers use the data as a starting point for setting sealing conditions on production equipment.

Link to ASTM F2029