From Invention to Global Utilization: Exploring the History and Development of PET

Polyethylene terephthalate (PET) emerges as a standout among plastic polymers, valued for its exceptional chemical stability, broad application potential, and notable recyclability. 

PET was first synthesized in 1941

Throughout history, humans have used natural polymers such as resins, natural rubber, and cellulose to create tools, utensils, and decorations. However, these materials had limitations in performance and supply, prompting the exploration of synthetic alternatives.

In the early 20th century, with the rapid advancement of science and technology, there was an urgent need for new materials to meet industrial and everyday demands. In 1907, Belgian chemist Leo Baekeland invented Bakelite, the first fully synthetic plastic. Bakelite was widely used in electrical appliances, automotive parts, and household items, overcoming the limitations of natural materials. This invention marked the beginning of the plastic industry and the dawn of synthetic polymers.

Polyethylene terephthalate (PET), now one of the three major synthetic polymers, was successfully synthesized in 1941 by British scientists J. Rex Whinfield and James T. Dickson at the Calico Printers' Association laboratory. They were building on earlier work by Wallace Carothers, an American chemist who had identified the polyester family in the 1930s. Whinfield and Dickson's breakthrough involved polymerizing ethylene glycol with terephthalic acid, resulting in the creation of PET, a polymer that would later become widely used in fibers for clothing, containers for liquids and foods, and thermoforming for manufacturing.

Initially, the research and applications of PET focused primarily on textiles, assessing its performance and suitability as a fiber. The results demonstrated that PET fibers had excellent mechanical properties and chemical stability, quickly establishing it as a significant player in the synthetic fiber market and paving the way for its expansion into other application areas.

Breakthrough from Textiles to Packaging

As scientists researched and developed PET for textiles, they gained a deep understanding of its superior physical and chemical properties, such as chemical stability, ease of molding, high strength, and toughness. 

In 1965, PET made a breakthrough in bottle applications when the Swiss company Vetrotex first used it for bottled water containers, showcasing PET's potential in the packaging industry, particularly its lightweight, durable, and transparent characteristics. In 1973, Nathaniel Wyeth invented the PET bottle and received a U.S. patent, marking a significant turning point in PET's application in packaging. PET bottles began to attract widespread attention and gradually entered commercial production.

Traditional glass bottles were prone to breakage during transport and use, whereas PET's strong mechanical strength and toughness made it an ideal alternative packaging material, reducing transportation losses and safety risks.

In the 1980s, with improvements in production technology, the growing demand for lightweight and durable packaging, and advancements in blow molding technology, large-scale production and widespread use of PET bottles were propelled. These factors profoundly changed the landscape of the beverage packaging industry, making PET bottles the primary material for beverage packaging.

Globally, PET production surpasses 70 million tons annually. Over half of the world's beverages are packaged in PET bottles, underscoring its pivotal role in packaging solutions. Furthermore, PET bottle recycling rates exceed 50% in numerous countries, with several achieving rates upwards of 80%.

Current Development Trends

In the face of escalating global environmental challenges, PET is steadily progressing towards high performance, multifunctionality, and sustainable development.

Production Capacity Concentrated in Asia, Especially China

Asia stands as the leading global region for PET production, boasting the largest capacity worldwide. China, in particular, holds the mantle of the world's foremost PET producer, with its bottle-grade PET capacity constituting approximately 40% of the global total. Projections indicate that China will continue to spearhead global PET capacity expansion, with expectations to account for 40% of new plant constructions and expansions by 2028.

China's significant capacity growth underscores its dominant position in the global PET market as one of its largest producers. The country plays a pivotal role in the international trade of bottle-grade PET resin, leveraging economies of scale and competitive pricing to maintain favor in global markets. Concurrently, China's PET industry is advancing towards higher quality standards, bolstering its international competitiveness through enhanced production efficiency and product excellence.

Ongoing R&D and Innovation in PET Materials

The modification of PET results in significant performance enhancements and broader application potential, establishing modification practices as a key industry trend. By refining the properties of PET, manufacturers can achieve targeted performance outcomes, driving innovation and meeting the specialized demands of diverse sectors. 

The research team at Wankai New Materials Co., Ltd. has identified that PET's high polymer chain free volume limits its barrier performance compared to metals and ceramics, allowing easier substance permeation. Currently, PET does not meet stringent barrier requirements for applications such as beer, beverages, electronics, OLEDs, and vacuum packaging against oxygen and water vapor. To enhance barrier properties, the team uses in-situ polymerization to better disperse inorganic nanoparticles in the matrix. This reduces PET chain free volume, strengthens gas permeation paths, and improves material barriers. They also optimize processing by adjusting nanoparticle concentrations, polyester viscosity, and carboxyl end groups, improving crystallization for polyester film stretching and thermal molding. Furthermore, Wankai has also made significant advancements in modifying other aspects of polyester.

Through PET modification to capitalize on its inherent strengths and address limitations, the objective is to drive its adoption in emerging applications. In the automotive sector, driven by the trend of lightweighting, by adding glass fiber reinforcements, the strength and rigidity of PET can be significantly enhanced, making it suitable for high-strength and wear-resistant applications such as car body parts and engine hoods, thereby improving vehicle fuel efficiency and safety. In the electronics field, surface treatments or the addition of static suppressants can improve PET's electrical insulation properties in electronic products, protecting components from static electricity and enhancing the stability and durability of devices, such as in electronic device casings and circuit boards.

New PET composites have significantly extended their application in advanced technology sectors, demonstrating exceptional performance in high-temperature, high-pressure, and corrosive environments.

The Boeing 787 Dreamliner incorporates PET composite materials in its internal structures and external components，contributing to reducing aircraft weight, enhancing fuel efficiency, and providing excellent corrosion resistance to meet the demands of long-term flight operations. Moreover, in the nuclear energy sector, PET composite materials are utilized in the manufacturing of nuclear reactor containment vessels, radiation shielding equipment, and nuclear fuel storage containers. These materials provide essential radiation shielding and chemical stability required for safe nuclear operations.

Sustainable Development as a Key Direction for PET

Balancing economic development with ecological protection is paramount. Guided by global sustainable development goals, the PET industry is actively pursuing efficient resource utilization and the implementation of circular economy models.

Various PET recycling methods continue to emerge, with chemical recycling technologies enabling the upgrade and regeneration of PET. Innovations like enzymes and microorganisms present substantial potential for advancing environmentally sustainable and efficient PET recycling processes. These sophisticated recycling and regeneration technologies convert discarded PET materials into recycled PET fibers, PET bottle materials, or other valuable chemical feedstocks, effectively prolonging material lifecycles and mitigating environmental footprint.

Recently, Zhink Group, parent company of Wankai New Materials, has partnered with France's Carbios to develop rPET using Carbios' enzymatic depolymerization technology. They plan to establish a PET waste recycling facility in China with an annual processing capacity surpassing 50,000 tons. This strategic initiative, leveraging advanced biological recycling technologies, aims to advance the circular economy in plastics and textiles, providing substantial benefits to global packaging and textile markets.

PET production is actively progressing towards sustainable practices with a strong emphasis on green and low-carbon objectives.

The use of clean and renewable energy provides important green power for polyester production. Wankai New Materials utilizes rooftop photovoltaic power generation, esterification waste heat recovery, biogas utilization, and comprehensive natural gas systems to substantially mitigate carbon emissions in the polyester production process. Additionally, the development of energy-saving technologies further conserve energy and reduce the environmental footprint of production. For example, Wankai's ethylene glycol (EG) off-gas treatment plays pivotal roles in conserving energy and minimizing the environmental impact of production. 

The development of bio-based PET and biodegradable PET signifies a move towards more environmentally friendly and sustainable PET materials, meeting the urgent demand for sustainability in society. 

Conclusion

PET's evolution highlights its resilience and versatility across industries. Initially valued for its chemical stability and recyclability, PET has revolutionized the packaging sector and expanded into high-tech applications through advances in production. As industries embrace eco-friendly practices and global demand for sustainable materials grows, PET's future holds further innovations toward a greener world.