Technical Datasheet Walkthrough (1/3)
What is a Technical Datasheet (TDS) ?
About grades of polymers
Countless kinds of plastics exist on the market, and they all have distinct properties, and can be used for an immense variety of applications. Each plastic is available in many different grades. That’s right, PLA is not one plastic, but many. So how do you differentiate your specific grade of PLA from another one that is also called “PLA” ? I’m glad you asked.
Each grade of polymer comes with its own Technical Datasheet (TDS), which gives all the specifications of this grade and thus differentiates it from the other polymers. A TDS is extremely useful, for it can help the reader predict the final properties of a 3D printed part. But even before talking about the 3D printed part, the TDS is often the key to process the plastic into filament.
Let’s insist a bit more, taking Polylactic Acid (PLA) as an example. It is important to understand that “PLA” does not refer to a specific material, but to a family of grades. It is true that all grades of PLA are similar, but they remain significantly different. The same goes for Thermoplastic Polyurethane (TPU): an injection molding grade behaves very differently than an extrusion grade.
Luckily, technical datasheets are here to help and tell us the difference between, say, an injection grade and an extrusion grade.
Where to find a TDS ?
It is impossible to find a TDS which covers an entire family. In other terms, there is no “PLA datasheet”. It is important to find the TDS which corresponds to the specific grade you are looking at. The TDS of a certain grade of plastic should be provided by the supplier of said plastic. Otherwise, it is also usually possible to find a TDS in online databases such as this one: http://www.matweb.com/search/getmatlsbymanufacturer.aspx?navletter=A
Content of a TDS: Why it is relevant for extrusion
The main purposes of a TDS are to give general information about the material (its applications for example), to quantify some of its properties, to warn the user about safety precautions, and to give processing recommendations.
The content may be classified in different ways, depending on the manufacturer, but it usually includes:
- General description of the material
- Pre-processing information
- Processing information
- Physical (mechanical, thermal, electrical) properties (viscosity for example)
Recommendations and hazards
Luckily, only a fraction of information is often required. Going back to the difference between an injection molding grade of TPU, and an extrusion grade, the main difference would be the viscosity: an injection molding grade needs to be be more fluid, in order to fill the mold easily, whereas an extrusion grade is typically more viscous. The viscosity value would be higher in the case of extrusion. In this simple instance, the reading of the datasheets has been rather simple. Trying to actually process a polymer takes just a bit more work, but preparation remains surprisingly simple.
To learn about the way to read a datasheet before a first extrusion test, click here.