Omar Khalid
Testing the strength of plastic is an important part of the product development and production process. Plastic testing helps ensure that materials meet safety, environmental, and aging requirements, and that they are suitable for their intended use. There are various methods for testing the strength of plastics, including tensile testing, flexural testing, impact testing, hardness testing, and shear strength testing. These tests can determine a plastic's elasticity, stiffness, resistance to deformation, impact strength, and more. Testing can also reveal the thickness and number of film layers in a plastic, as well as the types of materials used in its creation.
| Characteristics | Values |
|---|---|
| Tensile modulus (Young's modulus) | Measures elasticity under tension or compression |
| Flexural strength | Measures load required to cause 5% deformation/strain |
| Rockwell hardness | |
| Elongation at break | |
| Shear strength | |
| Impact | Izod impact test measures energy required to break notched specimens |
| Hardness | |
| Flammability | |
| Anti-fog characteristics | Specimen kept at 7-10 degrees for 24 hours |
| Oxygen permeation | Measures resistance to piercing or puncturing |
| Hot-tack testing | Evaluates hot sealing performance of packaging materials |
| Mechanical testing | Tests durability and performance under stress |
Explore related products
What You'll Learn
Tensile strength
Tensile testing is used to determine how plastics perform under controlled tension. A standardised specimen is placed in a testing machine, usually a universal tester, and pulled at a constant rate until it breaks or the maximum extension is reached. The speed depends on the specimen's shape and can range from 0.05 to 20 inches per minute. The target time from the start of the test to break should be between 30 seconds and 5 minutes. The displacement of the material is measured against the applied force to determine its tensile strength, yield point, tensile modulus, and other tensile properties.
Tensile modulus, also known as Young's modulus or stiffness, measures the elasticity of a plastic under tension or compression from a single direction. The elastic modulus, or modulus of elasticity, is the ratio of stress to strain below the proportional limit of the material.
Standardised tensile tests exist for various plastic materials, including films and injection-moulded plastics. Plastic films can be tested according to the ISO 527-3 standard, while injection and extrusion-moulded plastics are usually tested as per ISO 527-2. ASTM D638 is another common plastic tensile strength test specification for unreinforced and reinforced plastics, which uses "'dumbbell" or "dogbone"-shaped specimens. ASTM D882 is used to test the tensile strength of plastic sheeting in packaging materials.
Gold Leafing Plastic: A Guide to Gilding Synthetic Materials
You may want to see also
Explore related products
Flexural strength
To test the flexural strength of plastic, a specimen is placed on two supports spaced 4 inches apart. A load is then applied to the centre of the specimen at a specified rate. The loading at failure (psi) is the flexural strength. For materials that do not break, the flexural property given is usually the flexural stress at 5% strain.
The flexural strength test is similar to a tensile test, which is used to determine how plastics perform under controlled tension. However, flexural testing is easier to perform as it does not require a dog-bone-shaped test specimen.
The flexural test is also used to test concrete, and can be conducted using either a three-point load test or a centre point load test. The size of the specimen and the configuration of the test will depend on the specific standards being applied.
Attaining Plastic Perfection: A Guide to Mastering the Art
You may want to see also
Explore related products
Impact strength
Impact testing is used to determine the impact strength of a plastic material, which is a measure of its ability to absorb energy during collisions. This is important as it can be used to predict the amount of plastic deformation a material can endure before it fails. The impact strength of a plastic is determined by the impact energy and notch sensitivity of the sample.
There are several methods for impact testing, including the Charpy impact test and the Izod impact test. The Charpy impact test has been used since 1900 and remains one of the most widely used impact testing methods. It involves cutting notches into samples in accordance with industry standards, using a machine such as the GenNotch 2000. The notched samples are then hit by a weighted pendulum, and the energy absorbed by the sample is measured. The Charpy impact test is useful for comparing the shear fracture toughness of various materials under the same conditions or of one material at different temperatures.
The Izod impact test is an ASTM standard method of determining the impact resistance of materials. It involves raising a pivoting arm to a specific height, which corresponds to a constant potential energy, and then releasing it. The arm swings down and hits a notched sample, breaking it. The energy absorbed by the sample is calculated from the height the arm swings to after impact. The Izod impact test is useful for comparing various types and grades of plastics, but it is not a reliable indicator of overall toughness or impact strength. Some materials are notch-sensitive and derive greater concentrations of stress from the notching operation, which can affect the results of the test.
In addition to the Charpy and Izod impact tests, there are other types of impact testers, such as pendulum impact testers, high-speed testing machines, and drop weight testers. These traditional testers are simple, affordable, and reliable, but some researchers claim that they are low in repeatability and accuracy.
Rigging Plastic Lizards: The Ultimate Guide
You may want to see also
Explore related products
$27.37 $29.95
Stiffness
In addition to flexural modulus, the stiffness of plastics is sometimes referred to as flexural strength or tensile modulus. This mixing of terms can result in confusion regarding the difference between stiffness and strength. The strength of a plastic, typically referred to as tensile strength or ultimate strength, is how much stress a plastic can withstand without breaking when it is stretched or pulled. Stiffness, on the other hand, is the ability of the material to distribute a load and resist deformation or deflection.
Some plastic samples can be used to test the stiffness of the material. The weight of the sample is often proportional to its stiffness, with heavier samples feeling stiffer. The sound the sample makes when knocked on its edge can also indicate stiffness, with glass-reinforced plastics making a clanging sound and amorphous materials sounding rattly. Additionally, the sample can be twisted or bent to test its stiffness.
Some types of plastics are known for their stiffness. For instance, PEEK combines high stiffness (24,000 psi) with strength (14,000 psi) and outstanding chemical resistance. Ultem®, a PEI resin, offers high stiffness and strength, superior thermal resistance, and broad chemical resistance, with a flexural modulus of 22,000 psi. PPS also has an impressive flexural modulus of 21,000 psi and maintains its stiffness over a wide temperature range. Acetal is another stiff plastic with a flexural modulus of 14,300 psi, providing superior wear and abrasion properties as well as excellent chemical resistance.
Building a Plastic Set-Top Box: A Step-by-Step Guide
You may want to see also
Explore related products
![CMA Exam Study Material 2023-2024: Certified Medical Assistant Exam Prep Review and Practice Test Questions [2nd Edition]](https://m.media-amazon.com/images/I/51g1Jyh49KL._AC_UY218_.jpg)
Hardness
The Shore A hardness tester is another instrument used to assess the hardness of soft plastics, rubbers, elastomers, neoprene, and silicon. It features a hold function, a plastic case, and offers a resolution of 1° with 3% accuracy.
The Rockwell method is designed to eliminate the influence of surface roughness and measurement errors caused by play in the indentation depth measurement. It involves applying the total test force in two steps, measuring the indentation depth at a defined preload, and then calculating the Rockwell hardness (HR) using a formula that takes into account the Rockwell scale used.
Additionally, the hardness of plastics can be evaluated through fundamental and imitative mechanical testing. Fundamental testing is performed on standardised plastic pieces, while imitative testing assesses the performance of finished plastic products under specified mechanical stress, mimicking their intended use. These tests help identify potential flaws and ensure compliance with safety and quality standards.
Plastic Playing Cards: Magic Tricks' Best Friend?
You may want to see also
Frequently asked questions
The most common standard tests for plastic include checking its tensile and flexural properties, stiffness, impact, hardness, shear strength, and flammability. Tensile testing is used to determine how plastics perform under controlled tension. Flexural strength is the amount of load a plastic can take before it deforms.
You can test the strength of plastic yourself by performing a tensile test. During the test, a standardized specimen is placed in a testing machine (usually the universal tester) and pulled at a constant rate until it breaks or the maximum extension is reached.
Testing plastic is important to ensure that the plastic used is the one promised by the supplier. It also helps to ensure that the product meets the customer's safety, environmental, and aging requirements.
Other tests to determine the quality of plastic include the Izod impact test, hot-tack testing, oxygen permeation test, and anti-fog test.
