POLYETHYLENE
Polyethylene is a type of thermoplastic polymer that belongs to the polyolefin family. It is produced through the polymerization of ethylene and is one of the most widely used polymers across the globe constituting the largest fraction of global consumption. Its technical characteristics are influenced by such factors as molecular weight, crystallinity rate and molecular weight distribution. There are different densities of polyethylene available, including low-density (LDPE), medium-density (MDPE) and high-density (HDPE).
Low-Density Polyethylene was the first polymer produced commercially using ethylene. This solid material is partially crystalline and has a density that ranges from 0.91 to 0.94 kg/dm3. With a melting point of approximately 115°C, it is highly resistant to chemicals and acids, making it almost inert. Because of its unique properties, it is widely used in the food and agricultural sectors for flexible packaging, bags and films, usually through the extrusion process.
Linear Low-Density Polyethylene (LLDPE) has a linear molecular structure with minimal branching. This material is highly resistant to tearing, impact and punctures. It also has good resistance to chemical agents and excellent electrical properties. Additionally, it is very flexible and can stretch when pulled. This makes it ideal for creating thin films that are also strong.
Medium-Density Polyethylene (MDPE) has an exceptional ability to withstand impacts and falls. It is also highly resistant to environmental stress cracking, which means it won't break down when it comes into contact with fluids or swelling agents. MDPE is commonly used in the production of gas pipes, food tanks, industrial containers, building products, outdoor furniture and gardening items.
High-Density Polyethylene (HDPE) is known for its high molecular density, resulting in high stiffness and tensile strength. Additionally, its crystalline structure makes it highly resistant to chemicals and atmospheric agents. Due to these characteristics and its ease of processing, HDPE is ideal for a wide range of applications that use extrusion, injection moulding and blow moulding processes.
POLYPROPYLENE
Polypropylene (PP) is a widely-used plastic due to its semi-crystalline thermoplastic properties, thermal resistance, abrasion resistance, impact resistance, high ductility and low specific weight..
The "General Purpose Grade" is known for its exceptional stiffness, superior quality light colour, low density (0.900 - 0.906 gr/cm3) and outstanding chemical resistance. Although it has relative resistance to high temperatures, its impact resistance is limited, especially at low temperatures.
Block impact polypropylene copolymer (also known as ““block impact copolymer”) has better impact resistance than homopolymer, even at temperatures as low as -20°C. Adding impact modifier additives can further enhance its strength. The melting point of block impact copolymer is higher than that of "random" copolymer.
Random copolymer polypropylene is composed of propylene molecules that are randomly and irregularly inserted into the structure of ethylene molecules. It displays greater impact resistance, flexibility and lightness, compared to homopolymer.
