Introduction to plastics 

What is plastic?

It is considered as plastic to the group of materials that can be molded when soft and then hardened to retain the desired shape. There are synthetic (artificially created) plastics and natural plastics. We usually associate the word "plastic" with those synthetic materials that were created from natural, non-renewable raw materials such as oil, coal or gas that are heat-treated and converted into polymers (long molecules composed of small, repeating units called monomers) of ethylene and propylene. Eventually, the "pellets" (pellets) that are sent to the mills to be melted and molded into the desired shapes and articles (Figure 1).¹

Figure 1. "Plastic pellets

Types of plastics

There is a Plastic Identification Code which facilitates the classification of plastic into seven categories (Table 1).² The categories are distinguished by a number within a triangle created by three arrows, accompanied by acronyms. These acronyms indicate the chemical formulation of the type of material used to create the plastic article. Many people incorrectly think that the triangle symbol indicates that the item can be recycled, when it actually indicates the type of plastic it was made from.

Table 1. Identification code for each type of plastic, its uses and recyclability.²

Número y acrónimos	Type of material	Uses	Recyclability
	Polyethylene Terephthalate	Individual bottles of water, juice and soft drinks, Clothing	High
	High Density Polyethylene	Galones de agua, leche y jugo, Envases de limpiadores y detergentes, Envases de artículos para aseo como champús y acondicionadores, Bolsas	High (Except for the glossary)
	Polyvinyl Chloride	Tuberías, Materiales de construcción, Bandejas, Marcos para puertas y ventanas, Tarjetas de crédito	Download
	Low Density Polyethylene	Container closures, Food packaging, IV bags, Bottles and other flexible materials	Median
	Polypropylene	Tapas de botellas, Pañales, Envases para guardar comida, Neveras portátiles, Sorbetos (pajitas), Platos, Vasos, Ropa, Alfombras	Median
	Polystyrene	Vasos para el café y otras bebidas calientes, Platos, Vasos	Download
OTHER	Otros Plásticos (policarbonato, estireno, nylon, y mezclas de diferentes tipos de plásticos)	Biberones, Artículos electrónicos, Juguetes, Colchones	Download

References

1. This Is Plastics: How Are Plastics Made? Accessed February 9, 2023. https://thisisplastics.com/plastics-101/how-are-plastics-made/
2. Bilbao Villena A. Unhooking from plastic. Problems of a ubiquitous material: environmentalists in action. Accessed February 9, 2023. http://www.ecologistasenaccion.org

Author: María E. Ocasio Torres, Ph.D.
Bachelor's Degree in Coastal Marine Biology from the University of Puerto Rico - Humacao
D. in Biology from the University of Puerto Rico - Rio Piedras