Polyethylene terephthalate
Common thermoplastic polyester used in fibres and packaging.
Polyethylene terephthalate (PET, PETE, or obsolete PETP/PET-P) is the most common thermoplastic polymer resin of the polyester family. Its molecular structure consists of repeating C10H8O4 units. The polymer can exist in two forms depending on its processing and thermal history: an amorphous, transparent state, or a semi-crystalline state. The semi-crystalline form may appear transparent if its crystal particles are smaller than 500 nanometers, or opaque and white if the particles reach up to a few micrometers. The material is commonly recycled and is assigned the resin identification code 1 (♳). The National Association for PET Container Resources defines PET as a polymer derived from terephthalic acid (or dimethyl terephthalate) and mono ethylene glycol, where these monomers constitute at least 90 percent of the reacted mass, and which exhibits a melting peak temperature between 225 °C and 255 °C when tested under a specific ASTM procedure. Production involves synthesizing bis(2-hydroxyethyl) terephthalate, either through an esterification reaction between terephthalic acid and ethylene glycol (producing water as a byproduct) or via transesterification between ethylene glycol and dimethyl terephthalate (producing methanol). This intermediate then undergoes polycondensation to form the polymer, again with water as a byproduct. PET can also be obtained through recycling. In textile applications, the material is commonly called polyester, while the acronym PET is reserved for packaging uses. Including its use as polyester fibers, which account for over 60 percent of its production, PET is the fourth-most-produced polymer globally, after polyethylene, polypropylene, and polyvinyl chloride. Annual global production reached 31 million tons in 2025, with projections exceeding 40 million tons by 2031. Non-fiber applications, primarily packaging, represent about 6 percent of world polymer production by mass.
- field
- Polymer chemistry / Materials science
- known_for
- Most common thermoplastic polyester; used in polyester fibres and PET bottles
- patent_holders
- John Rex Whinfield, James Tennant Dickson, Calico Printers' Association
- annual_production_2025
- 31 million tons
- projected_production_2031
- over 40 million tons
- resin_identification_code
- 1 (♳)
Lore & Background
Polyethylene terephthalate is a thermoplastic polymer of the polyester family, composed of repeating (C₁₀H₈O₄) units. It appears either as a transparent amorphous material or as a semi-crystalline polymer that can be transparent (if crystal particles are smaller than 500 nanometers) or opaque and white (if particles reach a few micrometers). Its defining characteristic is a melting peak temperature between 225 °C and 255 °C, as measured by a specific ASTM procedure. The polymer is synthesized through esterification of terephthalic acid and ethylene glycol (producing water) or via transesterification of ethylene glycol and dimethyl terephthalate (producing methanol); polymerization proceeds by polycondensation. PET is the fourth-most-produced polymer globally, with annual production reaching 31 million tons in 2025 and projected to exceed 40 million tons by 2031. In textile applications it is commonly called polyester, while the acronym PET is used for packaging. Non-fiber uses account for about 6% of world polymer production by mass, while over 60% of PET is made into polyester fibers. It is widely recycled and bears resin identification code 1. PET is permeable to oxygen and carbon dioxide, which limits shelf life of packaged contents. Its biaxially oriented form (BoPET) can be aluminized to reduce permeability and create reflective, opaque films used in flexible food packaging and thermal insulation. PET compounded with glass fiber forms engineering resins for injection-molded parts.
Reader's Guide
Polyethylene terephthalate is a foundational material in modern life, serving dual roles as polyester fibre for textiles and as PET for rigid and flexible packaging. Its significance stems from its versatility: it is strong, impact-resistant, hygroscopic, and can be made transparent or opaque. In textiles, polyester fibres are widely used in fashion, thermal wear, sportswear, and automotive upholstery. In packaging, PET bottles dominate soft drinks, and multilayer structures extend shelf life for oxygen-sensitive beverages. Biaxially oriented PET (BOPET) film is used in flexible food packaging, space blankets, photovoltaic backsheets, and as a substrate in thin-film solar cells. PET compounded with glass fibre forms engineering resins for injection-moulded parts. Its ability to be recycled and its widespread use in 3D printing (as PETG) further underscore its importance. PET's legacy is that of a durable, adaptable polymer that underpins industries from apparel to renewable energy.
Did You Know?
- PET is the fourth-most-produced polymer after polyethylene, polypropylene, and polyvinyl chloride.
- PET can exist as both amorphous (transparent) and semi-crystalline (transparent or opaque) depending on processing.
- Biaxially oriented PET (BOPET) film is used in space blankets and as a backsheet in photovoltaic modules.
Frequently Asked Questions
Who is Polyethylene terephthalate?
PET (also called PETE or, in older literature, PETP/PET-P) is the flagship thermoplastic resin of the polyester family. It ranks as the fourth-most-produced polymer globally, trailing only polyethylene, polypropylene, and polyvinyl chloride.
What are PET's powers or main roles?
In textiles it goes by the name polyester, while in packaging it keeps its PET label. It serves as fibre for clothing, as the clear material for liquid and food containers, as thermoformed parts in manufacturing, and as a glass-fibre-reinforced engineering resin.
How does PET's story progress going forward?
Global output stood at roughly 31 million metric tons in 2025, and industry projections push past 40 million tons by 2031. That steady climb keeps PET firmly entrenched in the top tier of commodity plastics.
Why is PET so important to the polymer world?
It is the single most common thermoplastic polyester, giving it a dominant footprint across both consumer goods and industrial applications. Its resin identification code 1 (♳) is one of the most recognisable recycling symbols on the planet.
Who are PET's original creators?
The polymer was patented by John Rex Whinfield and James Tennant Dickson on behalf of the Calico Printers' Association. Their mid-twentieth-century work laid the groundwork for what would become a 31-million-ton-per-year global material.
More in Polymers And Macromolecules 1-24
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