Plastic Tensile Strain at Break Testing: Standards, Cost Factors, and Pricing Guide

Plastic tensile strain at break testing measures how much elongation a plastic specimen sustains before fracture and is one of the most frequently commissioned mechanical tests at accredited third-party laboratories. This guide explains how the test is performed under ISO 527, ASTM D638, and GB/T 1040, which sample types and test variables affect the testing price, and how to budget for specimen preparation, conditioning, and reporting.

Technical Overview

Strain at break, also known as elongation at break or nominal tensile strain at break, is the engineering strain recorded at the moment a plastic specimen fractures during a uniaxial tensile test. It is expressed as a percentage of the original gauge length and serves as a primary indicator of material ductility. Brittle materials such as unfilled polystyrene may show strain at break values below 2 percent, while ductile polyolefins and thermoplastic elastomers can exceed several hundred percent before fracture.

The test is performed on a universal testing machine equipped with grips matched to the specimen geometry, a load cell appropriate for the expected force range, and either a contact extensometer or a non-contact video extensometer for accurate strain measurement. Governing standards include ISO 527-1 and ISO 527-2, ASTM D638, GB/T 1040, and JIS K 7113. Because strain at break is highly sensitive to specimen geometry, surface quality, test speed, and conditioning history, laboratories must follow strict procedural controls, and these protocol requirements are also the main reason quoted prices differ between projects.

Testing Samples

Injection-Molded or Compression-Molded Dumbbell Specimens

The reference specimen for rigid plastics is the ISO 527-1A or 1B dumbbell, or the ASTM D638 Type I dog-bone. Clients may submit pre-molded specimens or request that the laboratory mold or machine them from pellets, plaques, or sheets, in which case specimen preparation fees are added to the base testing price.

Film and Thin Sheet Specimens

Plastic films are tested as rectangular strips under ISO 527-3 or ASTM D882 using lightweight pneumatic grips and long-travel or video extensometry. Film testing typically costs slightly more than rigid-specimen testing because of specialized fixturing, fragile handling, and the need for additional valid replicates.

Pipe, Profile, and Geomembrane Cut Specimens

Sections cut from pipes, profiles, sheets, or geomembranes are machined into standard shapes. Machining time, material waste, and the orientation of the cut relative to the processing direction all influence the final quotation.

Machined Specimens from Finished Parts

When testing supports failure analysis or incoming inspection of molded components, specimens are routed or milled directly from the actual product. This requires skilled operators and controlled feed rates to avoid heat damage, so machining is usually quoted as a separate line item.

Testing Items

A tensile strain at break test is normally bundled with the complete tensile property set, and accredited third-party laboratories typically quote one combined price for the package:

• Strain at break (elongation at break)
• Tensile strength at break and tensile stress at yield
• Tensile modulus, usually measured between 0.05 percent and 0.25 percent strain
• Strain at yield, and where required, Poisson's ratio
• Secant modulus and full stress-strain curve reporting

Conditioned-state testing, such as after heat aging, water immersion, chemical exposure, or UV weathering, is priced as a separate conditioning program plus the base tensile test fee.

Testing Methods

Specimens are conditioned at 23 degrees Celsius plus or minus 2 degrees and 50 percent relative humidity plus or minus 10 percent for at least 40 hours unless the product standard specifies otherwise. The specimen is gripped, a small preload is applied, and the machine extends it at a constant crosshead speed defined by the standard: 1 mm/min is used for modulus measurement on ISO 1A specimens followed by 50 mm/min for strength and strain at break, while ASTM D638 commonly specifies 50 mm/min for Type I specimens of standard thermoplastics.

Strain at break is determined from the extensometer signal at the instant of fracture. For materials that elongate beyond the extensometer travel, crosshead displacement may be used with a documented conversion, and this deviation must be stated in the report. A minimum of five valid replicates per condition is standard practice, and most laboratories retest specimens that fail outside the gauge length at no additional charge when a valid result cannot be obtained.

Optional method variants that increase cost include testing at elevated or sub-ambient temperatures inside an environmental chamber, high-speed tensile testing, testing after multi-week conditioning programs, and video extensometry for materials in which contact blades would trigger premature failure.

Testing Price and Cost Factors

Indicative pricing at accredited third-party laboratories generally falls within the ranges below, which should always be confirmed against the specific project scope:

• Standard room-temperature tensile package per material, five specimens, one direction: approximately USD 60 to 200
• Film tensile testing to ISO 527-3 or ASTM D882: approximately USD 80 to 250 per specimen set
• Specimen machining or molding preparation: approximately USD 10 to 50 per specimen depending on geometry and material
• Temperature-controlled chamber testing: typically a 30 to 100 percent surcharge on the base fee
• Conditioning programs such as heat aging, immersion, or UV exposure: quoted separately based on chamber time
• Express turnaround within 24 to 48 hours: commonly a 30 to 100 percent priority fee
• Bilingual or notarized reports and data-sheet-grade reporting: small documentation surcharge where applicable

The final quotation depends on the total specimen count, the number of test directions and conditions, the standard invoked, extensometer type, whether specimen preparation is included, and the required turnaround. Consolidating multiple materials or conditions into a single order usually reduces the per-set price.

Applications

• Quality control for resin producers, compounders, and injection molding operations
• Generation of material datasheets and grade comparison during material selection
• Verification of regrind content, batch consistency, and incoming material inspection
• Compliance files for automotive, packaging, medical device, and construction products
• Failure analysis to distinguish brittle fracture from ductile overload
• Research and development of filled, reinforced, recycled, and bio-based plastics

FAQ

How much does a plastic tensile strain at break test cost?

At most accredited third-party laboratories, a standard room-temperature tensile package for one material costs roughly USD 60 to 200, covering five specimens and the full set of tensile properties. Film testing, temperature-controlled testing, and conditioning programs are quoted higher. Always request a written quotation listing every included service.

How many specimens are required for a valid result?

ISO 527, ASTM D638, and GB/T 1040 require a minimum of five valid specimens per condition. For films, anisotropic materials, or components cut in multiple orientations, additional specimens are recommended, which increases the per-material price.

What is the typical turnaround time?

Standard room-temperature testing with conditioned specimens is usually completed within 3 to 7 working days after sample receipt. Projects involving machining, environmental chambers, or multi-week aging programs take correspondingly longer, and express service is available for a priority fee.

Should I choose ISO 527 or ASTM D638?

Both standards measure the same properties, but specimen geometry, test speeds, and modulus definitions differ, so results are not directly interchangeable. Choose the standard required by your customer, product specification, or target market, since retesting under a second standard doubles the cost.

Is specimen preparation included in the quoted price?

It depends on the laboratory and the incoming sample form. Testing of client-supplied ready-made dumbbells is the lowest-cost option, while molding, milling, or die-cutting of specimens from pellets, sheets, or finished parts is billed separately.

Why does film testing cost more than testing rigid specimens?

Films require dedicated pneumatic grips, long-travel or video extensometry, careful handling to avoid pre-damage, and more replicates to achieve statistically valid results, all of which increase labor time and equipment usage compared with standard rigid-plastic dog-bones.