Types of Plastics

Plastics are synthetic compounds derived from substances called polymers. In most cases, these polymers are derived from petroleum and chemical additives are added to achieve certain types of plastics. At the molecular level, they are long macromolecular chains of carbon atoms, obtained through the polymerization of natural or semi-natural substances such as petroleum derivatives, animal proteins and polysaccharides.

Plastics are synthetic materials that can be obtained through the polymerization of different resins, the most common previously being those of plant origin, such as cellulose, grain oil, formaldehydes such as furfural, and derivatives of coal and starch, among others. Currently the most common plastics are those derived from crude oil, which are first transformed into monomers and then into polymers.

The plastic state (or simply Plastic), is a state of malleability or properly plasticity of certain synthetic polymers.

This fluid state allows them to adapt, take on color and acquire more specific characteristics such as weight or resistance. To reach the plastic state, the polymers are heated and additives are added.

These additives give the plastic certain special characteristics, and they are also divided into categories based on their use.

Plasticizers increase the flexibility of polymers, antioxidants protect the plastic from oxygen degradation, stabilizers help make them waterproof. Dyes add color, and other additives give them various properties.

The types of plastics are classified according to the manufacturing process or their resistance.

Thermoplastic Plastics:

They are the plastics that transform into liquids when heated and then into a glass-like state when cooled, while at room temperature they remain flexible or plastic. These types of plastics are melted down and recycled into other forms. Plastic PP, PET, PE PS and some other recyclable plastics belong to this category.

Thermosetting plastics:

They are the plastics that once melted and molded become unalterable materials, although they are heated again, they do not melt again. They are generally the plastics that are obtained from an aldehyde, for example epoxy resins, melamine, phenol polymers, Bakelite and polyester resins. These plastics are not recyclable, since the chemical bonds between their macromolecular chains do not allow this material to return to the fluid state.

Within these two basic groups, there are several subcategories of plastics, these are classified according to the processes or additives that are added to them.

Main types of plastics:

PET or Polyethylene Terephthalate.-This plastic is very resistant and its degrees of hardness are also high. This polymer is obtained from ethylene, with molecules close together in their chains. In its primitive state it is colorless, odourless, resistant and non-toxic. With it, most containers, bags and plastic paper are manufactured, as well as clothing, waste containers, etc. Its melting temperature is 120°C and it has great resistance against chemical products. It is a plastic resistant to bases, acids, fats, and oils, it does not absorb moisture, it resists folds and stresses, so it is usually used to protect other elements, such as in the storage of food and beverages, such as bottles of pet, for soft drinks and water. This plastic is used in the form of plastic wrap, bags, plastic bottles, etc., and is easy to recycle.

Polypropylene or PEAD.- This plastic is very hard and resistant, even to heat and corrosive products. Due to its nature it is opaque and can be folded multiple times, in addition to the fact that it does not affect the environment. It is also obtained from ethylene, being made at temperatures below 70° C and at low pressures. Compared to plastics such as polyethylene terephthalate, it is more rigid, which is why it is used to create various objects. And since it is non-toxic, it is used to make various objects such as bags (for food and other uses), and various objects that take advantage of its durability and firmness, such as helmets, some structures and various objects.

Polyvinyl Chloride or PVC.- PVC is produced from petroleum, sodium chloride (salt) and natural gas to which additives are added in order to be used. Depending on the additives added to it, it acquires various properties, flexibility, rigidity, opacity, transparency, etc. This plastic is widely used, for example, in the manufacture of pipes and insulated electrical conduits, as it is very cheap. It is used in the production of toys, containers, wrappers, films, electrical appliances, etc. It stands out that it is highly toxic, mainly due to several of the additives that are added in the manufacturing processes, such as various heavy metals among other substances.

Low Density Polyethylene (LDPE).- This plastic is also produced from ethylene but it is made through high temperature and pressure processes. It is characterized by its transparency, elasticity and lack of rigidity. It is used to make flexible bags and as insulation in electrical cables.

Polystyrene.- It is produced from benzene and ethylene. It is a low-cost and hygienic material, so it is used for food containers, disposable cutlery, in the manufacture of thermal insulation, waterproof insulation, and other objects.

Bioplastics.- These are plastic substances made from certain animal proteins, such as those found, for example, in whey. These plastics can replace the current plastics used in food storage, since they are not toxic and can even be edible without harming the body. These plastics are biodegradable, so they do not affect the environment like other types of plastic, and can be quickly reintegrated into nature, since they are made from natural protein molecules transformed into plastic substances.

Also, within this group there are some plastics that are produced artificially, through the use of certain genetically modified bacteria, producing various plastic materials that can be used in industry and can even be used by applying them to animal and human tissues, thanks to have bio-compatible qualities, that is, that these types of biomaterials do not cause harmful or secondary effects when used in the human body (for example, in some type of prosthesis).