The testing cycle for tensile strain at break of plastic materials typically spans 5 to 10 working days, covering specimen preparation, conditioning, tensile testing to ISO 527 or ASTM D638, and final report issuance. Understanding what drives this timeline helps manufacturers plan product development, quality control, and certification schedules more effectively. This guide explains every stage of the testing period, the factors that extend it, and practical ways to shorten turnaround without compromising data integrity.
Technical Overview
Tensile strain at break, denoted as εB, is the engineering strain recorded at the moment a plastic specimen ruptures under uniaxial tensile loading. It is one of the most widely reported ductility indicators in material datasheets, alongside tensile strength and tensile modulus, and it plays a decisive role in material selection, part design, and batch acceptance decisions. Because plastics are viscoelastic and sensitive to temperature, humidity, processing history, and strain rate, the measured value of strain at break depends heavily on how the specimen is prepared, conditioned, and tested.
What Does the Testing Cycle Include?
The testing cycle, or turnaround time, is the total elapsed period from sample receipt at the laboratory to delivery of the signed test report. It is not simply the few minutes required to pull a specimen to failure on a universal testing machine. Instead, it aggregates several sequential stages: sample check-in and review, specimen preparation, environmental conditioning, instrument setup and calibration verification, test execution on multiple specimens, data validation, and technical review of the report. For routine tensile strain at break testing conducted by accredited third-party laboratories, the standard cycle is typically 5 to 10 working days, with expedited services of 3 to 5 working days available when project schedules demand faster results.
Key Standards Governing the Test
- ISO 527-1: general principles for determining tensile properties of plastics
- ISO 527-2: test conditions for moulding and extrusion plastics, including the 1A and 1B dumbbell specimens
- ISO 527-3: test conditions for films and sheets with thickness up to 1 mm
- ASTM D638: tensile properties of unreinforced and reinforced plastics using Type I through V specimens
- ASTM D882: tensile properties of thin plastic sheeting and films
- GB/T 1040 series: the Chinese national standard series technically aligned with ISO 527
- ISO 291 and ASTM D618: standard atmospheres for conditioning and testing of specimens
Testing Samples
Injection-Moulded Dumbbell Specimens
For thermoplastics, thermosets, and compounds, the reference specimen geometry is the dumbbell or dog-bone shape defined in ISO 527-2 (types 1A and 1B) or ASTM D638 (types I to V). These specimens may be supplied directly by the client or moulded by the laboratory from pellets or granules. When the laboratory performs the moulding, the cycle includes mould preparation, processing parameter stabilization, and a cooling period, which can add one to three working days before conditioning even begins.
Machined Specimens from Sheets, Rods, and Finished Parts
When material must be evaluated in its end-use form, specimens are machined from plates, rods, laminates, or actual components following machining practice consistent with ISO 2818. Machining introduces additional steps such as layout, milling, surface finishing, and dimensional inspection. Machined specimens also allow testing in different orientations, for example parallel and perpendicular to extrusion direction, which multiplies the number of specimens and can extend the overall testing period.
Plastic Films
Flexible films with thickness up to 1 mm are tested to ISO 527-3 or ASTM D882 using strip or dumbbell geometries cut from the roll. Film testing usually requires specimens in both machine direction and transverse direction, and the very high elongations of ductile films demand long crosshead travel and video extensometry, which slightly lengthens the test execution stage.
Pipes, Fittings, and Special Geometries
Segment specimens cut from pipes are tested according to the ISO 6259 series, while 3D-printed parts, textiles-reinforced sheets, and multi-layer structures may require custom specimen designs agreed between the client and the laboratory. Custom geometries typically require method confirmation runs, which should be factored into the quoted turnaround time.
Testing Items
Although tensile strain at break is frequently the headline parameter, a single tensile test campaign to ISO 527 or ASTM D638 normally delivers a complete tensile property profile, since all parameters are derived from the same force-extension curve. Commonly reported items include:
- Tensile strain at break, εB
- Nominal tensile strain at break, εtB, when crosshead separation is used beyond yield
- Tensile strain at yield, εY
- Tensile stress at yield and tensile strength, σY and σM
- Tensile stress at break, σB
- Tensile modulus, ET, measured at 1 mm/min or 5 mm/min depending on the standard
Testing a full property set does not usually extend the testing cycle compared with measuring strain at break alone, because the additional parameters are calculated from the same recorded data.
Testing Methods
Specimen Conditioning and Its Impact on the Cycle
Conditioning is the single largest fixed component of the testing period for plastics. In accordance with ISO 291, specimens are conditioned in the standard atmosphere of 23 ± 2 °C and 50 ± 5 % relative humidity for a minimum of 88 hours unless the material standard specifies otherwise, while ASTM D618 Procedure A specifies 40 hours at the same atmosphere for specimens up to 7 mm thick. For hygroscopic materials such as polyamides, dry-as-moulded testing or state-of-the-art moisture conditioning may be agreed, and moisture conditioning alone can occupy several days to weeks. This is why laboratories cannot compress the cycle below the conditioning requirement without compromising standard compliance.
Test Execution
Testing is performed on a calibrated universal testing machine fitted with appropriate grips and, for accurate strain at break, an extensometer or non-contact video extensometer. The gauge length is typically 50 mm for ISO 1A/1B specimens and 50 mm for ASTM D638 Type I specimens. Test speeds are selected from the standard tables, commonly 1 mm/min for modulus determination and 50 mm/min for strength and strain at break, with lower speeds used for brittle or reinforced grades. A minimum of five valid specimens per condition is tested per ISO 527-1 and ASTM D638, and more specimens are tested when scatter is high. Each individual test lasts from a few minutes for stiff materials to over thirty minutes for highly ductile films at slow speeds.
Typical Turnaround Time Breakdown
- Sample receipt, check-in, and scope confirmation: within 1 working day
- Specimen moulding or machining, if required: 1 to 3 working days
- Environmental conditioning at 23 °C / 50 % RH: 2 to 4 calendar days
- Machine setup, calibration verification, and test execution: 0.5 to 1 working day
- Data validation, technical review, and report issuance: 1 to 2 working days
Aggregating these stages yields a standard cycle of 5 to 10 working days for routine projects, and 3 to 5 working days when clients supply pre-conditioned, ready-to-test specimens and request priority scheduling.
Factors That Extend the Testing Cycle
- Insufficient or non-conforming specimens requiring re-moulding or re-machining
- Multiple test directions, temperatures, or strain rates requested in one project
- Hygroscopic materials requiring special moisture conditioning states
- Invalid failures, such as breakage inside the grips or outside the gauge length, triggering retests
- Very high-elongation materials requiring long-travel or non-contact extensometry setups
Applications
Tensile strain at break data with a well-defined and documented testing cycle supports a broad range of engineering and commercial activities across industries:
- Automotive: validation of interior trims, bumpers, clips, and under-hood components for ductility retention after heat aging
- Packaging: qualification of films and containers where elongation at failure governs drop resistance and seal performance
- Medical devices: verification of tubing, disposable housings, and sterile barrier materials against biocompatibility and mechanical specifications
- Pipes and construction: acceptance testing of pipes, fittings, and profiles against EN, ISO, and GB product standards
- Electronics and consumer goods: incoming inspection of resins and qualification of housings and structural parts
- Research and failure analysis: comparison of formulations, processing conditions, aging states, and recycled content levels
FAQ
How long does tensile strain at break testing take?
For standard-condition testing at 23 °C and 50 % relative humidity with client-supplied conforming specimens, the typical cycle is 5 to 10 working days, including the mandatory conditioning period and report review. Expedited processing can reduce this to 3 to 5 working days when the laboratory capacity allows.
Can the conditioning period be shortened to speed up the cycle?
No, not when standard compliance is required. ISO 291 and ASTM D618 define minimum conditioning durations, and accredited third-party laboratories will not issue standard-compliant reports without meeting them. Clients can, however, pre-condition specimens in their own facilities before shipment, provided the conditioning atmosphere is documented and the specimens are protected during transport.
How many specimens should I submit?
A minimum of five valid specimens per test condition is required by both ISO 527-1 and ASTM D638. Submitting eight to ten specimens per condition is recommended so that retests caused by invalid failures do not require a second sample shipment and a second cycle.
Does testing at multiple temperatures or speeds multiply the testing period?
It extends it moderately. Each additional condition requires its own specimen set and thermal stabilization, but test execution itself is fast. Most laboratories quote a modest incremental lead time for each additional condition rather than a full additional cycle.
What information should accompany the samples?
Clients should provide the material designation, the required test standard and specimen type, test direction where relevant, test speed and conditioning requirements, and any specification limits for the report conclusion. Complete information at check-in avoids clarification loops that are a common cause of turnaround delays.
Why is my film test taking longer than a rigid plastic test?
Filils tested to ISO 527-3 or ASTM D882 usually require specimens in both machine and transverse directions, exhibit very high elongations that extend each individual test run, and rely on non-contact strain measurement. These factors add time to the execution stage even though conditioning requirements are similar.