From polymer to useful granulates: what are thermoplastics?
Talent Plastics Tartu AS
A Swedish owned company from Estonia that supplies thermoplastic parts with injection moulding and inhouse assembly.
Talent Plastics Tartu is a company that has operated in the plastic industry for 21 years and hopefully many more years to come. Over time we have established many relationships with customers, suppliers; have gathered experience with numerous raw materials, parts and machines but even today we see that there is no limit to what plastic and the industry can offer us.
That and so many other reasons are why we want to give you a glimpse (or rather a grande exposé, we’ll see…) to what we experience daily. With this and other following articles we explain how and which materials we use (why (thermo)plastics even??), what is our machinery and injection moulding like, the quality system behind everything and many other topics that give a 360 degrees overview of our process. And what could not be a more perfect topic to start with then the star of the show today: plastic raw material. More specifically thermoplastics what we use and from what it all starts. We mostly hear today how there IS NO material so it would be good to fill the day at least of stories of the material we want to use and what wonders it can do. Eventually the raw material crisis will be over and just a bad memory (something that will become a cautionary tale for sure) but the value of such content can be cherished even after that.
The narrative is surely chosen because there are equally as many articles about plastic and why it is so bad.
But where to start? All over the internet and plastic industry companies’ website’s there is plenty of information of thermoplastics and what are its advantages. The narrative is surely chosen because there are equally as many articles about plastic and why it is so bad. The opinion, whether plastic is bad or not, is everyone’s personal thing. However, we hope that the information these articles give, is at least sufficient to establish better understanding and transparency of what and how is done within a plastic production company. Mainly because in so many occasions, it is not such common knowledge.
So, that being said, let’s get started! The business of plastics has a lot to do with chemistry and material science but there are aspects that help to understand easier what and how. It is perhaps the best to explain what thermoplastic are through the term polymer. Polymers are materials made of long, repeating chains of molecules. The materials have unique properties, depending on the type of molecules being bonded and how they are bonded. Some polymers bend and stretch, like rubber and polyester. Others are hard and tough, like epoxies and glass. (2) By plastic, it is meant that the engineering material is based on polymers, generally with various additives to give the material the desired properties, such as colours or softeners. How different polymers are divided based on their properties, can be seen in the following drawing (1):
Not to make things too difficult, we will focus only on thermoplastics – polymers that can be melted and recast almost indefinitely (3). Thermoplastics are in general divided into two categories. Semi-crystalline materials have a highly ordered molecular structure with sharp melt points. They do not gradually soften with a temperature increase, instead, semi-crystalline materials remain solid until a given quantity of heat is absorbed and then rapidly change into a low viscosity liquid. (4) Examples of semi-crystalline commodities are polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT) and polyethylene terephthalate (PET). Amorphous high temperature resins have a randomly ordered molecular structure which does not have a sharp melt point. Instead amorphous materials soften gradually as the temperature rises. (5) Most know examples are ABS, polystyrene (PS), polycarbonate (PC) and polysulfone (PSU).
Amorphous vs semi-crystalline thermoplastics (6)
Now that we have established in, perhaps a bit tricky words, what thermoplastics are, we want to support the technical with examples from real life. From the following table you can see which polymer is commonly used where:
Thermoplastics are everywhere...literally. With showerheads, I am sure a lot of people even did not think it is plastic, rather a shiny metal.. However, please note that this is just a small fraction of the different commodities out there. For example, Talent has processed over 150 different materials and we can, with confidence, say that all materials have their of challenges and while you might know the material, in injection moudling and thermoplastics processing, you never know 100% for sure what will come out of the mould before you actually have tried it. That is why it is critical to stress here that in this industry, testing a material and the tool thoroughly is a must. There is no easy fix. When one has endured the process from start to finish correctly, the result is that a product can run for decades.
When one has endured the process from start to finish correctly, the result is that a product can run for decades.
Maybe some of you wondered, when a particular commodity should be used or considered. Truthfully, there is not a good thumb rule for that. Rather designers, engineers and producers choose one from either experience or based on their research. Yes, for some materials (like mentioned above) you can make a generalisation but when requirements for parts/products change, this way the material previously chosen, might not work anymore. Here comes into play again that there is a possibility to mix additives to the polymers in order to achieve the most suitable material. It is a neverending balancing act of which are the right mechanical properties or which chemical resistance is needed and,?not to mention, the cost of it all. However, even when the research showed good results, in the moulding process, there is a possibility that the material will not work and one has to go back to the beginning or change compounds. It is a circle of events but eventually the balance is found.
Illustrative picture, Talent Plastics AB group gallery
To conclude, the world of plastics is very versatile but not impossible to understand. It is normal to think that you might even need a handbook for just to have all information to start with (and yes, we have a handbook, that you could read here). However, with the current article we hope that the world of plastic became a bit less dramatic and hostile, plus that it is not so confusing. Of course, it can be made very confusing with all formulas etc but that is not the goal in our mind. Rather a easy and digestable article of what is important about the topic. Feel free to comment what aspect/topic should be covered or rather explained in more detail. For us the next logical topic would be injection moulding technology overview but let’s see where to world will take us, maybe more critical and important topics come up.
Thank you for reading and take care!
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