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What is polyethylene (PE) and what is it used for?
It is a thermoplastic polymer with variable crystallinity, and depending on the type, it has a wide range of applications. Plasticine is one of the most widely produced plastics on the planet, with tens of millions of tons produced worldwide each year, making it the most abundant. PE's commercial process (the Ziegler-Natta catalysts) was developed in the 1950s by two scientists from different countries: Karl Ziegler from Germany and Giulio Natta from Italy.
Polyethylene is available in a variety of forms, each of which is best suited for a specific set of applications. In general, High-Density Polyethylene (HDPE) is much more crystalline than Low-Density Polyethylene (LDPE), and it is frequently used in situations that are completely different from those of Low-Density Polyethylene (LDPE). For example, low density polyethylene (LDPE) is widely used in plastic packaging, such as grocery bags and plastic wrap. HDPE, on the other hand, is commonly used in the construction industry (for example, in the fabrication of drain pipes). Ultrahigh Molecular Weight Polyethylene (UHMW) is a high-performance polymer that is used in a variety of applications, including medical devices and bulletproof vests.
The properties of polyethylene are as follows:
Now that we understand what polyethylene is used for, let's take a look at some of its most important characteristics. In terms of how the plastic reacts to heat, PE is classified as a “thermoplastic” (as opposed to a “thermoset”). When thermoplastic materials reach their melting point (110-130 degrees Celsius in the case of LDPE and HDPE, respectively), they become liquid. The ability of thermoplastics to be heated to their melting point, cooled, and reheated without significant degradation is a useful property. Instead of burning, thermoplastics such as polyethylene liquefy, making it possible to easily injection molding them and then recycle them. Thermoset plastics, on the other hand, can only be heated once (usually during the injection molding process). The first heating causes thermoset materials to set (similar to a 2-part epoxy), resulting in a chemical change that cannot be reversed. If you tried to heat a thermoset plastic to a high temperature a second time, it would burn. Because of this property, thermoset materials are poor candidates for recycling.
What is the process by which PE is created?
Similarly to other plastics, polyethylene begins with the distillation of hydrocarbon fuels (in this case, ethane) into lighter groups known as "fractions," some of which are then combined with other catalysts to produce plastics (typically via polymerization or polycondensation). Polyethylene is a thermoplastic material that can be recycled. You can learn more about the process by reading this article.
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