How to Read Material Data Sheets
Over the last century, the adoption of everyday plastics has greatly increased. With such a wide variety of plastic materials available for manufacturing, it is essential to determine which material best suits your project.
Plastic materials can differ slightly from each other or in radically different ways. Understanding how to read material data sheets is a great first step to understanding the difference in materials and determining the best material for your project.
This post will cover what material data sheets are for plastic manufacturing, and explain critical considerations you should make when reading these data sheets. For further information on plastic properties, contact our friendly team.
What are Material Data Sheets?
Material data sheets provide incredible detail about the individual properties of plastic materials. With a single glance, you can quickly understand what materials should be used for your project based on its needs. Most suppliers, including Afaridan Plastics, will readily provide basic material data and additional data upon request.
Each value shown in the material data sheet is based on international standards. This makes comparisons between similar grades of plastics more straightforward.
Material Data Sheet Limitations
Test methods cited in the material data sheet refer to tests completed under strict conditions with controlled temperature, load and time. As a result, material data sheets are best used as a reference or a snapshot of the potential of plastic materials.
As with most engineering fields, background knowledge on how to interpret the data is incredibly important. Skilled engineers should have the knowledge necessary to evaluate material properties and select the best materials based on your project.
Tensile strength refers to the resistance of the plastic breaking when under tension. This property is helpful for initially comparing the strength between materials; however, due to the nature of thermoplastics, we need to perform further tests to get the same depth of information. A tensile test is a relatively simple process in which a piece of material is placed between two clamps on a hydraulic press and is bent until it breaks.
Using this test, engineers can determine these properties:
Ultimate Tensile Strength: How much stress the material can handle before breaking.
Tensile Strength at Yield: How much stress the material can handle before deforming permanently.
Modulus of Elasticity: How much the material deforms when under stress
Elongation at Yield: How much the material can stretch before it snaps.
MPa: megapascal, which is 1,000,000 pascals (typical measurement for pressure)
GPA: Gigapascal, which is equivalent to 1000 MPa.
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In the above test, it can be determined that steel is 10 times stronger, 100 times stiffer, and can elongate to the same level as ABS. So should engineers give up on using ABS? Absolutely not. This measurement tells engineers that parts of the same strength must be thicker to perform to similar levels. ABS may be more suitable in some cases depending on the project and budget, which is why it is always important for engineers to fully understand projects before making material decisions.
Similar to tensile properties, flexural properties measure the flexural strength and flexural modulus and are often found to have the same values in homogeneous materials. However, for some plastics, flexural properties are important to measure as injection moulding may form a skin of material that does not match the rest.
To measure flexural properties, a three-point flexural strength test will be performed. This test involves bending the material as a bar across two supports with a hydraulic head pushing on the centre. This measures the flexural strength throughout the entire bar of material.
For materials such as steel, the flexural test will show similar results to the tensile test. However, for plastics, the flexural strength often differs throughout the cross-section.
Thermal properties explain how the temperature may affect the part. For metals, they may become brittle in the cold, whereas plastics may become soft when exposed to heat. Material data sheets will typically explain each material's thermal properties which are essential to consider based on the scope of your project.
Thermal property testing is a straightforward process in which the material will be exposed to different temperatures. The temperatures that the material deflects at will then be recorded.
Electrical properties are important for many industries, including automotive, aerospace, marine, packaging and consumer goods. There is a range of tests to determine key measurements for comparison. The main measurements to consider for plastic materials include:
Electrical resistivity: How strongly the material can resist an electric current. This is measured using Ohms-cm (or Ohms centimetre), which measures the bulk resistivity of a semi-conductive material.
Dielectric Constant: Used to determine the material's ability to store electrical energy. The dielectric constant is the ratio of the energy stored by two metallic plates with the tested material placed between them to the energy stored of the same plates with nothing between them. Typically if the tested material were to be used as an insulator, it would be ideal for the dielectric constant to be lower.
Energy Stored with Material
Energy Stored without Material
Dielectric strength: Refers to the electrical strength of a material as an insulator. Dielectric strength can also be defined as the maximum voltage to produce a dielectric breakdown. This measurement is assessed using the metric Kilovolt per millimetre. The higher the value for this measurement, the better the material is as an insulator.