Although plastics have only been used for around 100 years, they have become essential to everyday life. They are employed in almost every industry and application, including packaging, healthcare, construction, textiles, and consumer goods.
Six key polymer types (PET, HDPE, PVC, LDPE, PP, and PS) account for nearly 70 % of global manufacturing. These are commonly referred to as commodity plastics because they can be made in large quantities at a low cost, and remarkable material qualities are not required.
Some applications demand higher mechanical qualities and are classified as "engineering plastics" or "high-performance plastics", such as ABS, HIPS, PEEK, PTFE, etc. These materials are often more robust and necessitate more capacity testing than their "commodity plastics" competitors.
Determining mechanical characteristics is critical in designing, producing, and using polymer materials. Since its founding in 1970, the Testometric Company Ltd. has supplied universal testing devices to the plastics sector.
The Testometric range of machines can be used to determine a wide range of mechanical properties, including tensile, compression, flexural, shear, and adhesion.
Production Testing
Production testing aims to identify any need for corrective action in manufacturing, which is especially critical in plastics manufacturing processes like extrusion and molding.
Good quality control enables businesses to meet the demand for higher-quality products while ensuring that applicable criteria are satisfied.
Production and regular quality control testing necessitate using technologies that can give repeatable and accurate results in a timely and simple manner.
The WinTest Analysis EC software suite was created and developed for all user levels. Testometric's on-site or remote training and support offers users the confidence to define test definitions and start testing immediately.
All machine and software installations are tailored to each customer's needs, and Testometric can provide solutions for all production testing requirements.
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Research and Development
Determining material mechanical characteristics is critical in the research and development efforts of plastics and rubber industries. When developing production processes, it is essential to identify the mechanical qualities needed to meet the material specifications of new goods.
A thorough study of new materials and products is required to optimize these manufacturing processes.
Testometric's WinTest Analysis EC program is built to meet the most demanding R&D standards. It can generate complex, user-defined, multistage step testing for any material or product application. In addition to the extensive array of industry-standard calculations, user-defined calculations are fully adjustable.
Quality Control and Calibration
Before leaving production, every machine, grip, accessory, and software package is subjected to rigorous quality inspection. Testometric’s skilled and highly qualified engineers and developers thoroughly evaluate all packages to guarantee they are appropriate for the end user's intended application.
All machinery and devices are calibrated to internationally recognized standards and adhere to all significant variances of these standards.
Force:
- BS EN ISO 7500-1: Metallic materials — Calibration and verification of static uniaxial testing machines
- ASTM E4-21: Standard Practices for Force Calibration and Verification of Testing Machines
Displacement & Strain:
- BS EN ISO 9513: Metallic materials — Calibration of extensometer systems used in uniaxial testing
- ASTM E83: Standard Practice for Verification and Classification of Extensometer Systems
- ASTM E2309: Standard Practices for Verification of Displacement Measuring Systems and Devices Used in Material Testing Machines
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Testing and Demonstration Laboratory
Testometric’s factory has a well-equipped testing and demonstration facility and a large inventory of grips and fittings.
Testometric can arrange in-person demonstrations or provide demonstration videos for potential customers to display the quality of its products and provide complete assurance that accurate and trustworthy results can be acquired continuously.
Alternatively, test samples can be sent to Testometric’s laboratory, where its testing professionals will advise on the best method for testing these materials or items.
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Tensile Testing
Tensile testing is the most common type performed using universal testing equipment to evaluate various mechanical properties that provide vital information about plastic materials. Common qualities include ultimate tensile strength (UTS), elongation, modulus of elasticity, and yield strength.
Only these few properties can tell us a lot about a material and its behavior; they can tell us the maximum stress the material can withstand, whether the material is brittle or ductile by calculating how much the material deforms under stress, whether the material resists or allows deformation, and when the material will stretch beyond its recoverable limits.
This method of testing materials provides critical information to designers and engineers, allowing them to adjust and change the material's composition to achieve the desired mechanical properties.
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DER Double Eccentric Roller Grips. Image Credit: Testometric Company Ltd
DE-A2 Long Travel Extensometer. Image Credit: Testometric Company Ltd
Compression Testing
Compression testing is another important sort of testing performed on universal testing equipment that may show how a material reacts when subjected to a crushing, compressive load. This method allows for determining properties such as compressive strength, proportional limit, deformation, and yield strength.
In addition to identifying material qualities, compression testing can be performed on the final parts or components to show how the finished product will withstand the forces applied during its intended use.
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CPS Compression Platens. Image Credit: Testometric Company Ltd
CSJ D695. Image Credit: Testometric Company Ltd
Flexural Testing
Three- or four-point flexural testing evaluates the force required to bend a material beam and can be used to estimate a material's flexing resistance or stiffness.
Flexural modulus, which indicates how far a material can bend before permanent deformation occurs, is critical when constructing structural components or assemblies.
Because the physical properties of many materials, particularly thermoplastics, can vary greatly depending on ambient temperature, it is occasionally necessary to test materials at controlled temperatures that mimic the desired end-use environment.
The data can be used to choose materials for parts that will support loads without flexing or, conversely, for applications that require products to withstand a certain amount of movement before failing.
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VBTB3 Bend fixture for toothbrushes. Image Credit: Testometric Company Ltd
FSGB Flexural test fixture. Image Credit: Testometric Company Ltd
ASTM D638: Standard Test Method for Tensile Properties of Plastics
ASTM 638 specifies how to determine the tensile characteristics of standard and reinforced polymers using dumbbell-shaped test specimens and specific testing circumstances.
The test standard is intended to generate tensile property data for controlling and specifying plastic materials, as well as for qualitative characterization and research and development.
A universal testing machine with a consistent rate of crosshead movement is employed, together with either fixed or self-aligning grips. Different specimen clamps can be used and are chosen based on the material to be evaluated.
Testometric can provide manual, self-tightening, or pneumatic clamps with a wide range of gripping surfaces, including plain rubber, polyurethane, plain metal, serrated faces, textured faces, and many more. Some plastic materials are extremely sensitive to misalignment or surface tension, so it is critical to apply the appropriate gripping solution.
A load cell is used to measure the force applied to the test specimen when it is loaded into the grips. ASTM D638 requires precision to be equal to or better than +/- 1% of the specified force value, and the testing machine's accuracy must be confirmed in line with ASTM E4.
All Testometric load cells provide an accuracy of better than +/- 0.5% of the stated force down to as low as 1/1000th of the cell's full load capacity, allowing for the testing of specimens over a wide strength range.
For some material qualities assessed according to ASTM D638, extension measurements require a higher level of accuracy than crosshead movement.
In these instances, an extensometer can be used to measure the distance between two specific places within the test specimen's gauge length.
Testometric produces a wide range of contact and non-contact extensometers that meet the accuracy classification requirements for all types of plastics, including very stiff reinforced plastics and high-extension elastomers.
Calculations related to ASTM D38 include, but are not limited to:
- Tensile strength
- Percentage elongation at yield and break
- Modulus of elasticity
- Secant modulus
The wintest Analysis EC program is a fully integrated solution that meets all industry standards, including ASTM D638. Testometric can deliver software with the appropriate test standards pre-installed, making it easier for the end user to set up the system for testing.
Common international standards for tensile testing include
- BS EN ISO 527-1: Plastics. Determination of tensile properties. General Principles.
- ASTM D882: Standard Test Method for Tensile Properties of Thin Plastic Sheeting
BS EN ISO 178: Plastics – Determination of Flexural Properties
BS EN ISO 178 defines a 3-point loading method for determining flexural characteristics in rigid and semi-rigid polymers. This method can be used to analyze flexural behavior and calculate flexural strength, modulus, and other flexural stress/strain relationship parameters.
This approach works with a wide variety of plastic materials, including thermoplastic molding, extrusion, and casting materials, as well as filled and reinforced compounds, thermosetting molding materials, and thermosetting sheets.
A rectangular cross-section test specimen sitting on two supports is deflected by a loading nose operating on the specimen in the middle of the two supports. The specimen is deflected until it ruptures on its outer edge or reaches a maximum flexural strain of 5%, whichever comes first.
This test standard divides the obtained data into many classes with varying levels of complexity and correctness. All force measurements must be class 1 accurate to ISO 7500-1, although different classes of deflection measurement are necessary depending on the strain and modulus.
Testometric can provide equipment that meets the most demanding deflection measurement standards, ranging from crosshead displacement with compliance correction to direct measurement using laser deflectometers. These systems meet ISO 9513's deflection standards.
Wintest Analysis EC program is a fully integrated solution that meets all industry requirements, including ISO 178. Testometric can deliver software that includes the relevant test standards preconfigured for easy deployment by customers.
Common international standards for flexural testing include
- ASTM D790: Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials.
- BS EN ISO 14125: Fibre-reinforced plastic composites. Determination of flexural properties.
This information has been sourced, reviewed and adapted from materials provided by Testometric Company Ltd.
For more information on this source, please visit Testometric Company Ltd.