How to measure extensibility / elongation

Extensibility/Elongation refers to the degree to which a material can be stretched or extended before breaking. It is closely related to the material’s elasticity. This property is commonly found in raw and cooked baked goods (e.g., dough, pastry, noodles, molten cheese) and confectionery products (e.g., liquorice, chewing gum), textiles (fabrics and fibres) materials (plastics, rubbers).

Elongation is typically measured as the percentage change in length before fracture, providing a key indication of a material’s ductility or ability to deform plastically under stress. Materials such as metals, thermoplastics, and rubbers exhibit varying degrees of elongation, and this property is essential in industries requiring flexibility and durability, such as in crash barriers, car bumpers, and plastic hinges.

Elasticity vs. Extensibility: Elasticity refers to a material's ability to return to its original shape after stretching, while extensibility measures how far the material can stretch before breaking. Elastic materials may stretch to a certain point and then return to their original form, while highly extensible materials can stretch further, even if they do not fully recover.

Extensibility and elongation testing using a Texture Analyser is valuable in many industries, including textiles, materials science, and quality control. Below are key applications:

• Textile material stretch testing: Evaluating the extensibility and elongation of fabrics to determine their stretch properties by measuring the force required to stretch elastic fabric to a specified length. Textile materials like spandex or elastane have high extensibility, which allows them to stretch significantly without tearing, making them suitable for clothing that requires flexibility.
• Rubber and elastomer testing: Assessing the elongation and extensibility of rubber and elastomeric materials used in automotive and industrial components by stretching a rubber band to a specific length to evaluate its elasticity.
• Food: In bread dough, extensibility is an important quality that allows the dough to stretch without tearing during kneading or baking. High extensibility is essential for creating a strong gluten network. Mozzarella, has high extensibility, allowing it to stretch into long, thin strands when melted.
• Paper and film stretch testing: Measuring the elongation properties of paper, plastic films, and packaging materials by stretching plastic film to the point of tearing. Plastic films that need to be stretched (e.g., cling wrap) are tested for their ability to extend without tearing.
• Pharmaceutical film testing: Assessing the elongation of dissolvable pharmaceutical films used for oral drug delivery by stretching oral dissolvable film to assess its stretchability.
• Adhesive material stretch testing: Testing the elongation of adhesive materials like tapes and labels by measuring the force needed to stretch adhesive tape before it breaks.
• Textile fibre testing: Evaluating the elongation of individual textile fibres used in yarn and fabric production by stretching a single fibre to assess its stretchability. For example, silk and certain synthetic fibers exhibit high extensibility.
• Polymer film stretch testing: Assessing the elongation properties of polymer films used in packaging by stretching plastic wrap film until it tears.
• Foam material testing: Measuring the extensibility of foam materials used in cushioning by stretching a foam sample to assess its stretch properties.
• Tape and sealant testing: Testing the elongation and extensibility of construction tapes and sealants by stretching a construction adhesive sealant to assess its stretchability.
• Geotextile material testing: Evaluating the elongation of geotextile materials used in civil engineering and landscaping by stretching geotextile fabric to a specified elongation.

In these examples, a Texture Analyser applies controlled forces/distances to measure elongation and extensibility, helping manufacturers optimise materials for product development, quality control, and material characterisation.

In a typical extensibility/elongation measurement test, a sample is clamped at both ends and stretched at a constant rate until failure occurs – this is uniaxial tension testing. 

Occasionally, samples are clamped around their perimeter, exposing a circular region whereby their extensibility can be measured in a biaxial extension test.

The following probes allow successful holding of a product in order to test in a tensile manner:

Uniaxial tension

Heavy Duty Tensile Grips

Spaghetti/Noodle Tensile Rig

Kieffer Dough and Gluten Extensibility Rig

Cheese Extensibility Rig

Pizza Tensile Rig

Miller-Hoseney Toughness Rig

Capsule/Loop Tensile Rig

Biaxial tension

Film Support Rig

Tortilla/Pastry Burst Rig

Dough Inflation System

From the graph you can observe/obtain: 

• Tensile strength
• Burst strength
• Distance to burst
• Resistance to extension/Toughness
• Extensibility
• Stretch quality
• Elasticity
• Tug force
• Tear strength
• Elongation
• Breaking strain
• Energy to failure
• Yield stress/strain
• Resilience
• 0.2% proof stress
• Young’s Modulus

A full explanation of this curve and its analysis can be accessed within Exponent Connect software. Existing Exponent users can upgrade to Exponent Connect specification.

Below is a video example of how we can help you understand curve analysis for an example property. 

Brittle materials: Show a short linear region followed by sudden failure, with little or no plastic deformation. Brittle materials have low extensibility, breaking after minimal elongation. They typically exhibit a sharp rise in force and break quickly once their limit is reached.

Ductile materials: In materials science, ductility is a measure of how much a material can stretch before it breaks. Ductile materials exhibit high extensibility, meaning they can undergo significant deformation (elongation) before failure. They exhibit a clear yield point followed by a long plastic deformation region before failure.

Elastomers: Often show a non-linear curve from the start, with high extensibility and low Young's modulus.

• Temperature: The temperature of the sample during testing can impact its extensibility, as materials often become more pliable at higher temperatures.
• Strain rate: The speed at which the sample is stretched can influence the measured elongation.
• Sample preparation: Consistency in sample dimensions and handling is crucial for accurate measurements.

The Stable Micro Systems Texture Analyser stands out in optimising extensibility and elongation measurements through its comprehensive approach and advanced features. Equipped with specially designed tensile grips and sample holding attachments, it offers micron-level precision in deformation measurements.

The Texture Analyser’s versatility allows for various tests, including tensile strength and elongation to failure, across a wide range of materials from delicate films to robust industrial products. With high-speed data collection at 2000 points per second and a broad force range up to 750kg, it captures detailed force-distance-time profiles for in-depth analysis. 

Exponent Connect software provides comprehensive data interpretation which is backed by Stable Micro Systems' expertise, making it the ideal choice for industries seeking to refine product formulations and maintain quality standards in extensibility and elongation testing.