The Impact of Plastic Disposable Food Packaging Box Materials on Food Insulation

1. Analysis of Basic Characteristics of Common Plastic Food Container Materials

1.1 Material Classification and Basic Characteristics

• Polypropylene (PP, No. 5): A colorless, translucent, thermoplastic, lightweight general-purpose plastic with excellent chemical resistance, heat resistance, electrical insulation, and mechanical wear resistance. It can withstand high temperatures up to 130°C, has a density of approximately 0.90-0.91 g/cm³, and is one of the lightest types of plastic, also possessing good weather resistance.
• Polystyrene (PS, No. 6): Easy to process and mold, low cost, good corrosion resistance, electrical insulation, and printability. It is divided into general-purpose grade (GPPS) and high-impact grade (HIPS). It is a typical transparent plastic with a density of approximately 1.05 g/cm³, and has an aesthetically pleasing appearance, suitable for manufacturing products requiring high transparency.
• Polyethylene terephthalate (PET, No. 1): Commonly known as polyester resin, it is a crystalline saturated polyester, appearing as a milky white or light yellow highly crystalline polymer. It has high transparency, good barrier properties, is non-toxic and odorless, and has excellent hygienic safety. It is widely used in pre-packaged drinking water, fruit juice, and carbonated beverage bottles.
• Polyethylene (PE): Classified by density into low-density polyethylene (LDPE, No. 4), high-density polyethylene (HDPE, No. 2), and linear low-density polyethylene (LLDPE). HDPE has good heat and cold resistance, high chemical stability, strong rigidity and toughness, a waxy feel, and can withstand temperatures up to 100°C; LDPE is the lightest type of polyethylene, milky white, with good softness, extensibility, electrical insulation, transparency, and ease of processing.

1.2 Comparison of Physical Parameters

 

2. Thermal Insulation Performance Comparison and Analysis

2.1 Hot Food Thermal Insulation Performance Testing and Comparison

2.2 Cold Food Preservation Performance Evaluation

2.3 Analysis of Temperature Retention Time in Actual Use Scenarios

• Takeaway Delivery Scenario (ambient temperature 25℃, initial temperature 60-80℃): PP disposable food packaging boxes can maintain a temperature above 60℃ for 2-3 hours, suitable for general delivery; PS foam disposable food packaging boxes can maintain a temperature above 60℃ for 3-4 hours, suitable for long-distance delivery; PET disposable food packaging boxes can only maintain a temperature above 60℃ for 1-1.5 hours, not suitable for hot food delivery.
• Daily Carrying Scenario (ambient temperature 25℃, initial temperature 70℃): Ordinary PP disposable food packaging boxes provide insulation for 2-4 hours, meeting daily needs; double-layered hollow-designed PP disposable food packaging boxes provide insulation for 3-5 hours, suitable for long-term carrying; PS foam disposable food packaging boxes provide insulation for 4-6 hours, suitable for special insulation needs.
• Refrigerated Storage Scenario (ambient temperature 4℃, initial temperature 2-8℃): PP disposable food packaging boxes can maintain a temperature range of 2-8℃ for 8-12 hours; PS disposable food packaging boxes can maintain a temperature range of 2-8℃ for 10-15 hours; PET disposable food packaging boxes can maintain a temperature range of 2-8℃ for 6-8 hours.
• Ambient temperature significantly affects insulation performance. In winter, when the room temperature is below 15℃, the insulation time of plastic disposable food packaging boxes may be shortened to 1-2 hours; high temperatures in summer (>30℃) will accelerate food cooling, and in extreme environments, materials with better insulation properties or additional insulation measures should be chosen.

 

3. Comprehensive Safety Assessment

3.1 Chemical Stability under High Temperature Conditions

• PP material: Offers the best high-temperature stability, with a heat distortion temperature of 100-120℃, and can withstand temperatures up to 130℃. It is the only plastic material that can be safely heated in a microwave oven. Its molecular structure is stable, and it does not release harmful substances within the normal operating temperature range.  Its chemical properties are stable, with no toxic substances released, earning it the title of "safety champion" among plastic disposable food packaging boxes.
• PS material: Has poor heat resistance, with a heat distortion temperature of 75-100℃. It begins to soften at 75℃ and is not suitable for holding hot food. At high temperatures, it may release styrene monomers (classified as a "possible carcinogen" by the World Health Organization). Studies show that after 10 minutes of contact with 100℃ boiling water, PS disposable food packaging boxes release long-chain alkanes, which may cause inflammation and endocrine disruption.
• PET material: Has the worst heat resistance, with a heat distortion temperature of 70-80℃.  Temperatures exceeding 70℃ will cause deformation and release of harmful substances. It is commonly used in beverage bottles and is not suitable for holding hot food or heating.
• PE material: Heat resistance varies depending on density. HDPE can withstand 100℃, while LDPE has even poorer heat resistance, usually not exceeding 110℃, otherwise thermal melting will occur.

3.2 Risk Assessment of Harmful Substance Migration

• Plasticizer migration risk: Environments above 60°C accelerate the release of phthalates (plasticizers) from plastic disposable food packaging boxes. At 60°C, the migration amount reaches 0.5 mg/kg, exceeding the EU standard by 2 times; at 80°C, the release of bisphenol A (BPA) soars to 1.2 μg/L, and long-term intake may interfere with the endocrine system.
• Microplastic release risk: At high temperatures, plastic disposable food packaging boxes release a large number of microplastic particles. When containing food at 78-85°C, PP containers release approximately 12,000 particles/cm² within 15 minutes, and PS containers release 35,000 particles/cm²; at 100°C, the microplastic release reaches 1.2 billion particles per liter, which can enter the bloodstream through the digestive tract, posing a potential health threat.
• Special case: PVC disposable food packaging boxes have the highest risk. After containing braised eggplant at 60°C for 30 minutes, the migration amount of plasticizers exceeded the national standard limit by 11 times.  Its use in food packaging is currently prohibited.

3.3 Compliance with Food Contact Safety Standards

• Chinese Standard System: GB 4806.7-2023 "National Food Safety Standard - Plastic Materials and Products for Food Contact" (effective September 6, 2024), integrating resin and product standards, prohibiting the use of recycled materials, requiring food-grade raw materials, total migration ≤10mg/dm² (aqueous simulant) or ≤60mg/kg (fatty simulant), bisphenol A migration ≤0.05mg/kg, and heavy metals (calculated as Pb) ≤0.01mg/kg.
• EU Standard System: (EU) No 10/2011 specific standard for plastic materials and products, with total migration requirements consistent with China, but stricter bisphenol A migration requirements (≤1μg/kg), prohibiting the use of bisphenol A-containing materials in baby bottles, and emphasizing traceability and GMP regulations.
• US FDA Standard: 21 CFR Part 177 classifies and regulates plastic materials, specifying the scope and limits of use for plastic resins and additives, and requiring that the materials do not alter the odor, color, or composition of food.

3.4 Long-Term Health Risk Assessment

• PP material: Lowest long-term risk; chemically stable under normal use and does not release harmful substances. However, inferior PP may contain plasticizers, and is easily corroded when containing strong acidic/alkaline foods.  It is necessary to choose food-grade PP products from reputable manufacturers.
• PS material: Higher long-term health risk; styrene monomers released at high temperatures have potential carcinogenicity, and long-term contact may increase the risk of cancer; plasticizer migration in disposable food packaging boxes may also interfere with the endocrine system and affect reproductive development. PET material: Relatively safe in itself, but has poor heat resistance. Improper use (such as holding high-temperature food) may release plasticizers; the risk increases with repeated use, potentially releasing harmful substances such as heavy metal antimony.
• PE material: The risk mainly comes from plasticizer migration, which is more likely to occur when in contact with oily foods. Long-term consumption of food containing plasticizers may lead to metabolic diseases such as obesity and diabetes.

4. Comprehensive Evaluation and Application Suggestions

4.1 Multi-dimensional Comprehensive Scoring System

• Thermal Insulation: PP gets 5 points extra for being microwaveable; PS has excellent thermal insulation but is not microwaveable, so it gets 28 points minus 2 points; PET has poor heat resistance, only 18 points; PE series have high thermal conductivity, scoring 12-15 points; PLA modified to withstand temperatures up to 120℃ gets 22 points. Safety: PP is the only microwave-safe and chemically stable material, scoring 24 points; pulp is a natural material, scoring 25 points; PS releases styrene at high temperatures, scoring only 15 points; PET has poor heat resistance, scoring 18 points; PE has good chemical stability, scoring 19-20 points; PLA is a bio-based material, scoring 23 points.
• Environmental Friendliness: PLA is completely biodegradable, scoring 24 points; pulp is biodegradable and recyclable, scoring 23 points; PP is recyclable but difficult to degrade, scoring 15 points; PE series are difficult to recycle, scoring 12-13 points; PS has extremely low recycling value, scoring 10 points.
• Cost-effectiveness: PS has the lowest price, scoring 19 points; PP has the highest cost-effectiveness, scoring 18 points; PE series has moderate prices, scoring 15-16 points; PET has a higher price, scoring 15 points; PLA costs 2-3 times more than PP, scoring only 12 points; pulp has the highest cost, scoring 10 points.

4.2 Material Selection Suggestions for Different Application Scenarios

• Takeaway Delivery: First choice: PP (keeps warm for 2-4 hours, withstands 120℃, high safety); Second choice: PS foam (keeps warm for 4-6 hours, suitable for hot food that does not require reheating); Alternative: PLA (environmentally friendly, suitable for high-end takeaways).
• Daily Carrying: For hot food, choose PP (microwaveable, reusable); for cold food, choose non-foamed PS (high transparency); for high-end needs, choose PET (exquisite appearance).
• Restaurant Dining: Fast food chains choose PP (high cost-effectiveness, suitable for bulk use); high-end restaurants choose PET/PLA (enhances brand image); children's meals choose PP (safest, avoids BPA-containing materials).
• Special Scenarios: Airline catering chooses certified PP/special materials (meets aviation safety standards); medical meals choose PP (suitable for high-temperature sterilization, sterile and non-toxic); outdoor catering chooses PS foam (portable and good insulation).

 

5. Summary

• Thermal Insulation Performance: PP (thermal conductivity 0.11 W/(m・K), withstands 130℃) is the best overall, suitable for hot food; PS foam provides the longest insulation (4-6 hours), but is not microwaveable; PET/PE have high thermal conductivity and are more suitable for cold food. Safety: PP is the only plastic that is safe for microwave use, releasing no harmful substances at high temperatures; PS releases styrene at high temperatures (a potential carcinogen); PET/PE should avoid high temperatures and grease to prevent plasticizer migration.
• Environmental Friendliness: Traditional plastics (PP/PS/PET/PE) are difficult to degrade; PLA degrades in 3-6 months in industrial composting, reducing carbon emissions by 60%-80%, and its heat distortion temperature has exceeded 120℃, with costs reduced to 16,000 RMB/ton.
• Cost-effectiveness: The procurement cost of PLA is 1.7-2.3 times that of traditional plastics, but the comprehensive cost index (1.7) is lower than that of traditional plastics (2.0-2.5); PP (0.35 RMB/piece) remains the market mainstream.