Q&A: Comprehensive Introduction to PETG Copolyester

Q1.What is PETG and how is it produced?

A1: PETG is a thermoplastic material. PETG stands for Polyethylene Terephthalate Glycol-modified. It is a type of amorphous copolyester that belongs to the family of transparent plastics. PETG is synthesized through the copolymerization of three monomers:

• PTA (Purified Terephthalic Acid)
• EG (Ethylene Glycol)
• CHDM (1,4-Cyclohexanedimethanol)

PETG is essentially PET modified with CHDM as a comonomer, which improves its properties such as transparency, impact resistance, and ease of processing.

Q2.How does PETG differ from PET?

A2: PETG differs from standard PET because it incorporates CHDM as a third monomer. Key differences include:

Material	Composition	Key Advantage
PET	PTA + EG	High strength, low cost
PETG	PTA + EG + <50% CHDM	High transparency, toughness
PCT	PTA + CHDM	Excellent heat resistance
PCTG	PTA + EG + >50% CHDM	Higher rigidity, durability

Q3. What are the main properties of PETG?

A3: PETG offers several excellent properties:

• High Transparency: Provides glass-like clarity, making it ideal for packaging and display purposes.
• Impact Resistance: Exceptional toughness to resist breakage under impact.
• Thermoformability: Perfect for producing thick-walled transparent products.
• Low Shrinkage: Ensures superior dimensional stability.
• Good Processability: Can be easily cut, machined, and modified after production.

Q4. What are the applications of PETG?

A4: Thanks to its outstanding clarity, toughness, and ease of processing, PETG is widely used in:

• Food and Beverage Packaging: Premium transparent containers and thermoformed trays.
• Medical Devices: Transparent medical packaging and surgical tools.
• Cosmetic Packaging: Clear bottles and containers for cosmetic products.
• Electronics: Protective casings and clear displays for electronic devices.

Q5. What is the significance of viscosity in PETG products?

A5: The intrinsic viscosity (IV) of PETG determines its suitability for different applications. We have previously introduced the IV in our article “Introduction of Polyester Chip Index.” For more details, please click here.

PETG’s viscosity can be adjusted post-production to meet diverse customer requirements.  

Q6. How do NPG and CHDM impact PETG performance as third monomers?

A6: NPG (Neopentyl Glycol) and CHDM (1,4-Cyclohexanedimethanol) are two key third monomers used to modify PETG. They have different effects:

Parameter	NPG (Neopentyl Glycol)	CHDM (1,4-Cyclohexanedimethanol)
Structure	Straight-chain, stable	Ring structure, rigid
Key Advantage	High transparency, toughness	Better heat resistance, rigidity
Disadvantage	Lower heat resistance	Slightly reduced transparency
Recommended Ratio	5% – 15%	10% – 30%
Processing	Lower melt viscosity, easy to process	Higher melt viscosity, requires higher processing temperatures
Applications	High-end cosmetic packaging, medical tools	Heat-resistant food packaging, industrial parts

Q7. How does PETG compare to other thermoplastic polyesters like PET, PBT, and PEN?

A7:

Material	Advantages	Disadvantages	Applications
PET	High strength, recyclable, low cost	Poor heat resistance, brittle	Bottles, films, fibers
PBT	Good heat resistance, electrical properties	Lower mechanical strength, costlier	Automotive, electronics
PETG	High transparency, impact resistance	Moderate heat resistance, higher cost	Food packaging, displays, medical devices
PEN	Superior heat resistance, high barrier	High cost, complex processing	Specialty packaging, optical films

Q8. Why is PETG considered ideal for thick-walled transparent products?

A8: PETG has excellent thermoformability and low shrinkage, which allow it to be easily processed into thick-walled transparent products without defects like bubbles or warping. Its impact resistance also ensures durability in such applications.

Q9. How does PETG’s compatibility affect its applications?

A9: The compatibility of PETG plays a crucial role in its applications, especially when blended with other high polymers. Good compatibility expands PETG’s potential for use in a wide range of applications. For example, polycarbonate (PC) is an engineering plastic known for its excellent gloss, toughness, and heat resistance. But it has poor chemical resistance, stress crack resistance, and processing properties. When PETG exhibits good compatibility with PC, it significantly improves these shortcomings.

Currently, PETG blending systems being researched include PC/PETG, PET/PETG, PBT/PETG, and LCP/PETG. Experimental results indicate that PC/PETG, PBT/PETG, and PET/PETG exhibit good compatibility in terms of morphology and mechanical properties. When PETG content is high, the mutual compatibility of these blends is further enhanced. However, LCP/PETG has poor compatibility. With LCP acting as a nucleating agent in the blend, leading to crystallization of PETG and affecting its performance.

PETG has strong growth prospects in technical aspect. Its excellent compatibility with other polymers allows it to expand into more industrial and consumer applications.

Q10. What are the main manufacturers of PETG and what is its market outlook?

A10: The production of PETG is primarily dominated by Eastman (USA) and SK Chemicals (South Korea). The two companies that have long monopolized the supply of CHDM (Cyclic Hexamethylene Terephthalate). Eastman and SK Chemicals employ an integrated production model, combining upstream raw materials with downstream copolyester products. So it ensures their leading position in the global PETG market.

With the increasing global emphasis on environmental protection and health policies, the market outlook for PETG films is promising. According to data from 2022, the global PETG film market reached a value of USD 398 million. And it is expected to grow to USD 738 million by 2029, with a compound annual growth rate (CAGR) of 10.46%. PETG films are primarily categorized into three types based on shrinkage rate:

• Shrinkage rate ≤ 60%
• 60% < Shrinkage rate < 75%
• Shrinkage rate ≥ 75%

Among these categories, PETG films with a shrinkage rate ≥ 75% had a sales value of USD 203 million in 2022, accounting for 51.14% of the market share. This share is expected to increase to 53.33% by 2029, with a CAGR of 11.10% from 2023 to 2029.

PETG is a versatile copolyester material with superior transparency, impact resistance, and processability. It is widely applied in food packaging, medical devices, cosmetics, and electronics. Its performance can be tailored through viscosity adjustment and third monomers like NPG and CHDM. So it can meet diverse industry requirements. For products demanding high clarity and toughness, PETG remains an ideal solution.