Major Types of Plastics, Markings, Applications, and Properties

Plastic (plastic mass) is the common name for materials whose main (and sometimes sole) component is macromolecular substances. These can be natural or synthetic polymers.

Plastic can be made from:

• pure polymer (for example, polymethyl methacrylate, polystyrene, polyethylene);
• copolymers;
• polymer blends.

It is also derived from polymers that:

• modified by chemical methods (e.g., hydrolysis);
• modified by physicochemical processes (e.g., degradation);
• contain substances such as plasticizers, fillers, stabilizers, as well as dyes and pigments.

Properties of Plastic

Different types of plastic have different mechanical and chemical properties, but it can be assumed that most of them share the following characteristics:

• completely waterproof;
• low density;
• low resistance to high temperatures;
• lack of electrical conductivity;
• resistance to numerous chemicals, such as acids, oils, etc.;
• ease of processing.

However, it is important to remember that polymer materials are extremely diverse, so there are exceptions to virtually all of the characteristics mentioned above.

Types of Plastics and Markings

To understand how and with what to glue, weld, degrease, or melt plastic, you always need to know exactly what material you’re dealing with. Only then can you ensure that you’re using the right substance for the specific task at hand—one that won’t damage the plastic. The labeling on each plastic product is very helpful here; it allows you to quickly identify the type of material you’re working with.

Plastic labeling:

1. PET (PETE) — polyethylene terephthalate. It is a dielectric material characterized by its strength and wear resistance. It is insoluble in any organic solvent or water. Polyethylene terephthalate can be used to make containers for liquids, such as beverages or household cleaning products. It is a component of some synthetic fibers used in the production of clothing or technical devices. It also finds applications in many other fields.
2. HDPE is high-density polyethylene. It is resistant to water and does not react with acids or alkalis. It can degrade when exposed to nitric acid (a 50% solution at room temperature), as well as fluorine and chlorine. HDPE is used to make food wrap, bags, disposable tableware, and other materials. Products made from this polyethylene can be recycled using various recycling methods.
3. PVC—polyvinyl chloride—is the third type of plastic marking. It is completely colorless, meaning it is transparent. This material is chemically resistant to mineral oils, solvents, alkalis, and most acids. Polyvinyl chloride is used to manufacture window and door profiles, linoleum, and artificial leather. It is not resistant to ultraviolet rays.
4. LDPE — low-density polyethylene. It can be used in the same applications as the previous materials (except for rigid products and various types of bottles). This type of plastic is one of the safest.
5. PP stands for polypropylene; it is the fifth plastic symbol. It is not as dense as polyethylene, but it is more resistant to abrasion. It is also virtually unaffected by temperature. Corrosion cracking has almost no effect on it. This type of polypropylene can be used to make packaging materials for perishable foods, baby food bottles, and various transparent tubes.
6. PC — polystyrene. It is used in thermal insulation projects, as well as in the manufacture of bottles, food containers, and disposable tableware.
7. O is the marking for other types of plastic products. They are most commonly used in construction.

Uses of Plastic

Materials traditionally used to manufacture various types of packaging, such as wood, glass, or metals, are rapidly being replaced by plastics. It is estimated that about 20–25% of packaging is made of plastic. These often take the form of various types of films.

Bottles are also made from plastic using a process in which hollow containers are formed by blow molding. Rigid polystyrene packaging has a very important and widespread use. In construction, plastic is used for interior finishing. Among other things, it is used to manufacture various types of flooring, as well as window and door frames. Plastic is also used for roofing.

Various types of plastics are widely used in everyday life. Many devices and pieces of equipment are made from them. Plastics also serve various functions in agriculture. For example, polyethylene film has significantly increased the potential for growing crops in greenhouses. It is used both as a structural element and as a covering for the supporting structure.

The examples described above are just a few of the ways plastic has found its way into our daily lives. Everyone should be aware that, from time to time, we use objects or devices made from some kind of synthetic material. Today, it is hard to imagine a world without plastic. It has become an integral part of everyone’s daily life.

All About Plastic: Pros and Cons

Although the use of plastics has its drawbacks, ultimately, this material clearly has more advantages. For example:

• the ability to easily create even very complex and irregular shapes (a good example is 3D printers or molds used in injection molding);
• low weight;
• high mechanical strength;
• the durability of the products being manufactured;
• good electrical insulation properties;
• high chemical resistance;
• recyclability (if the waste is sorted);
• light tinting.

The main drawbacks of plastic include:

• low resistance to high temperatures;
• a very long decomposition time (plastic waste takes many tens or even hundreds of years to decompose);
• susceptibility to creep (i.e., a slow change in shape resulting from the action of this object or material under constant and prolonged loads).

Now you know how plastics are labeled and the properties of different types. Plastics aren’t as dangerous as people thought for many years—provided, of course, that they’re handled properly. Given how long it takes for plastic to decompose (some types take up to 1,000 years!), it’s important to remember that used or broken items made of polymer materials should be disposed of in recycling bins.

This will not only help keep our environment in better condition, but will also indirectly affect the prices of plastic products—since manufacturing them from recycled materials is very inexpensive.