Technical guide by Plasticalia Chemical
How to read a plastic's technical data sheet
A plastics technical data sheet is full of figures, units and standards. We explain what each property means and what to look for to choose the right material.
Typical values or specifications
The first thing is to know what kind of data you are reading. Most data sheets give typical values: manufacturer averages that serve as a guide but are not a guarantee. Specifications (with minimums, maximums or tolerances) are, and what is guaranteed for each batch is the certificate of analysis. If a property is critical for you, ask for it.
The properties, one by one
| Property | Unit | What it tells you |
|---|---|---|
| Melt flow index (MFI / MFR) | g/10 min | How easily it flows when molten. It determines the process: low for extrusion and blow moulding, high for injection moulding. More about the melt flow index. |
| Density | g/cm³ | In polyethylene, the higher it is, the more rigid. It distinguishes HDPE, MDPE, LLDPE and LDPE. |
| Tensile strength (at yield or at break) | MPa | The force the material withstands under tension before it deforms or breaks. |
| Elongation | % | How far it stretches before yielding or breaking: it indicates ductility. |
| Flexural modulus | MPa | Stiffness: the higher it is, the less the part bends. |
| Izod or Charpy impact | J/m or kJ/m² | Resistance to impact. Check the test temperature: at −20 °C many materials become brittle. |
| Vicat temperature | °C | The temperature at which it starts to soften: the limit for use at high temperature. |
| Heat deflection temperature (HDT) | °C | The temperature up to which a loaded part holds without deforming. |
| Hardness (Shore D, Rockwell) | — | Resistance to scratching and indentation. |
| ESCR | hours | Resistance to stress cracking in contact with detergents or chemicals. Key for packaging. |
| Intrinsic viscosity (PET) | dl/g | The “melt flow index” of PET: higher for carbonated drink bottles. |
| Dart, Elmendorf, haze, gloss (film) | g, g/µm, % | Puncture and tear resistance, and the optical properties of the film. |
ASTM and ISO standards
Each value comes with the standard used to measure it: ASTM (American) or ISO (international). They measure the same thing but with somewhat different test specimens and conditions, so only compare values measured to the same standard and under the same conditions (temperature, load, speed).
Old units
Some data sheets give strength in kg/cm² or psi. To convert to MPa: kg/cm² ÷ 10.2 and psi ÷ 145.
Food contact
If the material is going to be in contact with food, look for the reference to Regulation (EU) No 10/2011 (and, where applicable, the FDA) and ask for the up-to-date declaration of compliance: some older data sheets cite standards that have since been repealed.
All the data sheets in our catalogue are in web format, with their original PDF. If you have a question when comparing them, ask us.