A Comprehensive Guide to Polyethylene Terephthalate

Polyethylene terephthalate (PET) is one of the most widely used thermoplastic polymers in the world, known for its versatility, durability, and recyclability. Its applications span various industries, from packaging to textiles and beyond. At Alfa Chemistry, we recognize the significant impact PET has on modern manufacturing, and our commitment to advancing materials science involves a deep understanding of this exceptional polymer. This article provides a detailed scientific overview of PET, focusing on its synthesis, properties, and key industrial uses.

View a wide range of PET products to find the best option for your application:

Main Products

Catalog	Product Name
PL-MP-25038599	Poly(ethylene terephthalate), Crystallinity<20%, 50-200 um

Granule

Catalog	Product Name
PL-PET-A077	PET Granule (3-4 mm granule size)

Powder

Catalog	Product Name
PL-PET-A078	PET Powder (16 mesh)
PL-PET-A079	PET Powder (20 mesh)
PL-PET-A080	PET Powder (32 mesh)
PL-PET-A081	PET Powder (50 mesh)
PL-PET-A082	PET Powder (80 mesh)
PL-PET-A083	PET Powder (100 mesh)
PL-PET-A084	PET Powder (150 mesh)
PL-PET-A085	PET Powder (200 mesh)
PL-PET-A086	PET Powder (300 mesh)
PL-PET-A087	PET Powder (500 mesh)
PL-PET-A088	PET Powder (800 mesh)
PL-PET-A089	PET Powder (1000 mesh)
PL-PET-A090	PET Powder (1500 mesh)
PL-PET-A091	PET Powder (2000 mesh)

For more PET products, please click:

PET Sheets & Rods

PET Films

What is Polyethylene Terephthalate?

Polyethylene terephthalate, commonly referred to as PET, is a high-performance aliphatic polyester. It is synthesized through the reaction of ethylene glycol with terephthalic acid or its derivatives. PET's unique molecular structure gives it a combination of rigidity, strength, and flexibility, making it an ideal choice for a variety of applications. In its natural state, PET is a colorless, semi-crystalline resin that can be semi-rigid or rigid depending on its processing.

How is Polyethylene Terephthalate Made?

The synthesis of PET primarily occurs through two chemical reactions: esterification and transesterification.

A. Esterification Reaction: This process involves the direct reaction of terephthalic acid with ethylene glycol. The esterification reaction is conducted under high temperature and low pressure, where water is removed as a byproduct, driving the reaction forward.

B. Transesterification Reaction: In this method, ethylene glycol reacts with dimethyl terephthalate (DMT), forming PET and methanol as a byproduct. This reaction is typically performed at elevated temperatures.

After the initial reaction, the resulting oligomers undergo a polycondensation reaction where the chain length increases, producing a molten, viscous PET mass. This mass can be directly spun into fibers or molded into various shapes, making PET a versatile material for multiple applications.

Fig.1 Synthesis scheme of PET^[1].

Chemically, PET shares similarities with polybutylene terephthalate (PBT) but distinguishes itself with its higher thermal stability, strength, and broad processing versatility.

Properties of Polyethylene Terephthalate

PET's distinct characteristics stem from its molecular structure, which provides a balance of mechanical, thermal, and chemical properties.

Mechanical Properties

• High Strength and Stiffness: PET exhibits higher tensile strength and stiffness compared to similar polymers like PBT, making it ideal for structural applications.
• Impact Resistance: It possesses excellent impact resistance, offering durability in various environmental conditions without shattering.
• Dimensional Stability: PET maintains its shape and structural integrity under stress, contributing to its widespread use in precision molding.

Thermal Properties

PET has a glass transition temperature (Tg) between 65-80°C and a melting temperature ranging from 240-270°C, depending on its crystallinity. These properties enable PET to perform efficiently across a broad range of temperatures.

PET can reach a crystallinity of 40-50%, which enhances its mechanical strength and thermal stability. Crystallization occurs optimally at approximately 10°C above its Tg and up to 10°C below its melting point, with the maximum crystallization rate at 178°C.

Chemical Properties

• Resistance to Chemicals: PET exhibits excellent resistance to alcohols, aliphatic hydrocarbons, oils, grease, and diluted acids. It shows moderate resistance to diluted alkalis, aromatic, and halogenated hydrocarbons.
• Barrier Properties: PET's low gas permeability, particularly to carbon dioxide, makes it an excellent barrier material for food and beverage packaging.

Optical and Electrical Properties

PET can be processed to achieve high optical clarity, making it suitable for transparent applications such as bottles and films.

It offers excellent electrical insulating properties, which are critical in electronic components and applications requiring reliable insulation.

Environmental and Regulatory Aspects

• Recyclability: PET is one of the most recycled plastics globally, playing a significant role in reducing environmental impact. It can be reprocessed into new PET products, conserving resources and energy.
• Food Safety: PET is approved for food contact by regulatory agencies such as the FDA, Health Canada, and EFSA, making it a safe choice for packaging consumables.

Polyethylene terephthalate's unique combination of properties and ease of processing have made it a staple material in industries ranging from packaging to automotive and electronics. As a leader in chemical innovation, Alfa Chemistry continues to explore the potential of PET, enhancing its applications through advanced research and development. Whether through its superior mechanical properties, impressive thermal stability, or excellent barrier characteristics, PET remains a cornerstone material for modern manufacturing.

Through a commitment to innovation and sustainability, Alfa Chemistry aims to support industries in harnessing the full potential of PET, ensuring that this versatile material continues to meet the evolving demands of global markets.

Reference

1. Mihucz VG, et al. (2015). "Occurrence of Antimony and Phthalate Esters in Polyethylene Terephthalate Bottled Drinking Water." Applied Spectroscopy Reviews, 51(3), 183-209.