1. Introduction
In the modern food packaging industry, polypropylene (PP) and polyethylene terephthalate (PET) are widely used as mainstream thermoplastics. PP is a semi-crystalline polymer, and the methyl groups branching from its main carbon chain give it excellent chemical resistance and flexibility. It can withstand continuous temperatures up to 146°C and has strong resistance to acids, bases, and solvents. PET is formed by the polycondensation of terephthalic acid and ethylene glycol. The aromatic rings in its linear chain structure create a "tortuous path," giving it excellent transparency, durability, and barrier properties, especially in gas barrier performance.
2. Comparison of Basic Properties of PP and PET Materials
2.1 Molecular Structure and Basic Properties
PP is a semi-crystalline thermoplastic with a density of 0.89-0.92 g/cm³. It is lightweight, has a processing temperature of 220-280°C, requires moderate energy consumption, and does not require complex drying treatment, resulting in significant cost advantages.
PET is a highly crystalline polymer with a density of 1.33-1.45 g/cm³. Its transparency is close to glass, but it requires processing temperatures above 280°C and strict drying; otherwise, its transparency and strength will be affected. However, its lightweight characteristics can reduce transportation costs.
2.2 Comparison of Physical Properties
PP has excellent toughness and fatigue resistance, and its performance does not degrade even after repeated bending and stretching, making it suitable for food to go containers that are frequently opened, such as food storage containers. Its low-temperature resistance range is -20~-30℃, which is superior to PET's -10~0℃, making it more suitable for frozen food packaging.
PET has higher strength and hardness, with a tensile strength of 40-70 MPa, far exceeding PP's 20-40 MPa. It is impact-resistant and dimensionally stable, making it suitable for heavy-duty or long-term pressure-bearing applications such as beverage bottles and pharmaceutical packaging.
2.3 Comparison of Chemical Properties
PP has outstanding chemical stability and can withstand strong acids and bases such as hydrochloric acid, sulfuric acid, and sodium hydroxide. It is suitable for packaging acidic foods such as yogurt and fruit juice, as well as foods with complex chemical properties. Its barrier properties against water vapor and alcohol are also superior to PET.
PET exhibits good resistance to organic solvents and oils, but has weak resistance to strong acids and bases. It offers excellent barrier properties against oxygen and carbon dioxide, making it the preferred choice for carbonated beverage packaging, effectively maintaining the fizziness and freshness of beverages.
3. Food Application Scenario Adaptability Analysis
3.1 Hot Food Application Scenarios
PP has a continuous use temperature of up to 146°C and can withstand temperatures above 100°C. It is the only plastic suitable for microwave heating and is widely used in takeaway fast food, bento food to go containers, and hot food delivery packaging. It combines good sealing and structural stability, preventing spills. PET has a heat resistance limit of only 70-80°C; exceeding this temperature can easily cause deformation and potentially release harmful substances. It is only suitable for packaging warm foods that do not require heating. Although specially treated heat-resistant PET (such as CPET) can withstand temperatures above 160°C, it loses its transparency advantage.
3.2 Cold Food Application Scenarios
PET has high light transmittance, clearly displaying the color and form of food, enhancing consumer purchasing desire. It is suitable for packaging cold foods that require visual display, such as sushi, salads, desserts, and fresh fruits and vegetables. It maintains strength and toughness at low temperatures, making it suitable for refrigeration and freezing. PP is translucent or milky white; although its transparency is insufficient, it can subtly showcase the thick texture of yogurt packaging, and its low-temperature performance is superior, making it suitable for long-term frozen food storage.
3.3 Liquid Food Application Scenarios
PET has excellent gas barrier properties, accounting for 100% of the global carbonated beverage packaging market. It is also suitable for packaging liquids such as mineral water, fruit juice, and edible oil, offering advantages in high transparency, lightweight, and impact resistance. PP is suitable for liquid foods requiring hot filling, such as high-temperature sterilized condiments, and has better water vapor barrier properties, making it competitive in liquid packaging with high moisture resistance requirements. It is a commonly used material for edible oil packaging, along with HDPE.
3.4 Dry Food Application Scenarios
PP has strong moisture resistance and puncture resistance, and high chemical inertness, allowing it to safely package dry goods such as snacks, nuts, rice, and flour, preventing moisture penetration and food spoilage, and protecting fragile items from damage during transportation and storage. PET, with its high transparency, is suitable for packaging snack foods such as biscuits and candies that require visual display, helping consumers intuitively judge product quality and enhancing purchasing confidence.
4. Key Performance Indicator Comparison
4.1 Safety Assessment
PP is FDA certified (21 CFR 177.1520), BPA-free, and exhibits low chemical migration under normal use, especially at typical storage temperatures, where its chemical inertness prevents the release of harmful substances. PET also meets FDA standards (21 CFR 177.1630), is subject to strict regulations, and is safe and reliable when using new or compliant recycled materials. However, it may release trace amounts of acetaldehyde above 70°C, so high-temperature use should be avoided; furthermore, prolonged contact with organic solvents and high temperatures may release acetaldehyde, bisphenol A, etc., requiring careful selection of application scenarios. Both materials have passed national food-grade safety certifications and are safe for daily use, but care should be taken to avoid damage to the surface of PP containers to prevent increased chemical migration risks.
4.2 Heat Resistance Analysis
PP has a melting point of 160-170°C and a continuous use temperature of 146°C. It can withstand hot filling and microwave heating, making it a core material for hot food packaging, such as microwaveable meal containers, food to go containers, and hot food takeout packaging. Standard PET is heat-resistant up to 60-70°C and easily deforms at higher temperatures. While heat-resistant PET solves the temperature resistance problem, it loses transparency, limiting its applications. It is mainly used for food packaging that does not require heating.
4.3 Chemical Resistance Comparison
PP has excellent resistance to most acids, bases, and solvents, performing stably in dairy and acidic food packaging, and has strong oil resistance, making it suitable for oily food packaging. PET has good resistance to organic solvents and oils, but its performance deteriorates in strong acid and strong alkali environments. It is only suitable for most conventional food packaging, such as carbonated beverages and juices, and is not suitable for prolonged contact with organic solvents.
4.4 Recyclability Assessment
PET is one of the most recycled plastics globally, with a recycling rate of 52%. The recycling rate in the United States is 3.5 times that of PP. Bottle-to-bottle recycling technology is mature, and recycled PET (rPET) can be used to manufacture new beverage bottles, packaging, or textile fibers. In some regions, high-quality rPET is more expensive than virgin PET, and the recycling system is well-established. The recycling rate of PP is only 8%, due to difficulties in collection and sorting, high processing costs, and the challenges posed by its melting point and density characteristics. However, PP's contamination resistance is only 1/10 that of HDPE or PET, making it suitable for food-grade recycling. Furthermore, technologies such as near-infrared spectroscopy sorting, chemical recycling, and single-material design are gradually improving its recycling efficiency.
4.5 Cost-Benefit Analysis
In terms of raw material costs, the global average price of PP in 2023 was $968/ton, lower than the $1,161.90/ton for PET in 2022; in March 2025, the price of PP was approximately $1,054/ton, while rPET reached $1,810/ton. Regarding processing costs, PP has a lower processing temperature and does not require drying, resulting in lower energy consumption and processing costs. However, PET's lighter weight (20% lighter than PP for the same volume) can reduce transportation costs, and its high transparency and barrier properties increase the added value of high-end packaging. A comprehensive life cycle cost analysis requires considering multiple factors, including materials, processing, transportation, and recycling.
5. Multi-Dimensional Perspective Analysis
6. Regulatory and Standard Requirements
6.1 European Union Regulatory System
The EU uses (EC) No 1935/2004 as a framework regulation, requiring food contact materials to be harmless and not alter food characteristics; (EU) No 10/2011 specifically addresses plastics, clarifying the list of substances and migration limits (total migration ≤60mg/kg food or 10mg/dm² material). The 2025 amendment (EU) 2025/351 optimizes the definition of "additives," expands the scope of regulation, and refines requirements for recycled plastics. PP must comply with polyolefin regulations, and PET must meet polyethylene terephthalate requirements; both must pass migration tests.
6.2 United States Regulatory Requirements
The US FDA uses 21 CFR 170-199 as its core framework. PP follows 21 CFR 177.1520, requiring the use of approved raw materials, and migration testing covers multiple types of food simulants, with a total migration limit of ≤10mg/inch². PET, according to 21 CFR 177.1630, strictly controls catalyst residues (such as antimony), with antimony release from PET water bottles stored at room temperature for three years being less than 1 ppb. In addition, products must be labeled with "FDA Compliant," resin identification codes (such as "PP5" and "PET1"), and usage temperature information. California Proposition 65 also requires warnings for hazardous chemicals.
6.3 Chinese Regulations and Standards
China's regulations are centered around the GB 4806 series. GB 4806.1-2016 stipulates four fundamental requirements: harmlessness, compliance, process safety, and complete labeling; GB 4806.7-2016 specifically addresses plastics, clarifying indicators such as total migration (≤60mg/kg) and specific migration limits. GB 4806.10-2025 (to be implemented in September 2026) will include paper-based packaging coatings under regulation, and GB 4806.16-2025 will establish a dedicated standard for silicone rubber for the first time. Testing must be conducted by CMA and CNAS-accredited institutions according to the GB 31604 series. The total migration limit for infant food packaging is stricter (≤30mg/kg), and microwave packaging requires labeling of temperature and precautions.
6.4 Other Important Market Regulations
Japan's Food Sanitation Law requires materials to be certified by the Ministry of Health, Labour and Welfare, with strict control over heavy metals, formaldehyde, and other harmful substances; Canada's CFIA uses health risk assessment, with stricter restrictions on BPA than in Europe and the US, prohibiting its use in baby bottles; the Australia New Zealand Food Standards Code focuses on allergens and requires thorough risk assessment; South Korea's MFDS implements a "positive list system," where only substances on the official list can be used in food contact materials, resulting in strict regulation. All national regulations focus on ensuring health, clarifying standards, and strengthening supervision; companies need to adapt to the requirements of their target markets.
7. Summary
PP and PET food to-go containers each have their advantages: PP excels in heat resistance, chemical stability, and cost-effectiveness, making it suitable for hot food, frozen food, hot-filled liquids, and moisture-proof dry goods packaging; PET is superior in transparency, strength, and gas barrier properties, making it suitable for cold food, carbonated beverages, and display packaging. Both have passed safety certifications, and while PET has a more established recycling system, the recycling potential of PP needs further development. At the regulatory level, all countries have established strict regulatory systems, and companies must ensure compliance.
It is recommended that food companies select materials based on product characteristics and usage scenarios, manufacturers strengthen R&D of environmentally friendly and high-performance materials, and consumers use and recycle products correctly. In the future, with technological and regulatory advancements, both materials will continue to innovate, driving the food packaging industry towards a safer, more environmentally friendly, and sustainable direction.
