When choosing disposable plastic burger to-go boxes, polypropylene (PP) is the best choice for heat resistance, with a heat resistance temperature of 130-140℃. It is the only plastic material approved for microwave heating. In contrast, polystyrene (PS) has poor heat resistance (70-90℃), polyethylene terephthalate (PET) has the worst heat resistance (only 70℃), and polyethylene (PE) also has unsatisfactory heat resistance (70-110℃).
I. Classification and Identification of Disposable Plastic Food Container Materials
1.1 Main Material Types and Characteristics
The main materials of disposable plastic burger to-go boxes include polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyethylene (PE). These materials differ significantly in molecular structure, physical properties, and heat resistance.
Polypropylene (PP): The most commonly used heat-resistant food container material. It is colorless and translucent, and has good chemical resistance, heat resistance, electrical insulation, mechanical properties, and wear resistance. PP containers are usually soft, transparent, or translucent, and the general operating temperature range is -6℃ to +120℃. Modified PP can be used at temperatures from -18℃ to +110℃.
Polystyrene (PS): Harder and transparent, but easily torn. It is very stable at room temperature, but begins to soften when heated to 75℃, and decomposes into styrene gas at high temperatures. PS has excellent low-temperature performance and is an ideal packaging material for refrigerated foods such as ice cream.
Polyethylene terephthalate (PET): has poor heat resistance, with a maximum operating temperature not exceeding 70℃. It easily deforms when heated or filled with hot water, and can release harmful substances. PET is commonly used in mineral water bottles and beverage bottles, and is not suitable for use as burger to-go boxes.
Polyethylene (PE): is divided into high-density polyethylene (HDPE) and low-density polyethylene (LDPE). HDPE has good heat and cold resistance, good chemical stability, high rigidity and toughness, and a waxy feel. LDPE is the lightest type of polyethylene resin, is milky white, and has good flexibility, extensibility, electrical insulation, transparency, and ease of processing.
1.2 Material Identification Methods
Different plastic burger to-go boxes can be identified mainly by observing the recycling symbol number on the bottom. This triangle, formed by three arrows connected end-to-end, represents recyclability, and the number in the middle of the triangle (1-7) is the code for the type of plastic, using numbers and English abbreviations to indicate the type of resin used in the plastic. The specific numerical coding correspondence is as follows:
No. 1 (PET or PETE): Polyethylene terephthalate, commonly used in beverage bottles and food packaging.
No. 2 (HDPE): High-density polyethylene, commonly used in milk bottles, detergent bottles, etc.
No. 3 (PVC): Polyvinyl chloride, commonly used in plastic pipes and some food packaging; not recommended for food storage.
No. 4 (LDPE): Low-density polyethylene, commonly used in shopping bags and food packaging.
No. 5 (PP): Polypropylene, commonly used in microwaveable burger to-go boxes and yogurt cups; it is the only safe material for microwave use.
No. 6 (PS): Polystyrene, commonly used in disposable tableware and foam plastics.
No. 7 (OTHER): Other types of plastic products, including various other plastic materials.
II. Detailed Comparison of Heat Resistance of Different Materials
2.1 Comparison of Heat Resistance Temperature Ranges
According to the differential scanning calorimetry (DSC) test data, there are significant differences in the thermal performance parameters of different materials:
| Material | Operating Temp (°C) | Tg (°C) | HDT (°C) | Tm (°C) |
| PP | -20～120 | -10～-20 | 100～120 | 160～170 |
| HDPE | -40～120 | -125 | 75～85 | 130～135 |
| LDPE | -60～90 | -110 | 40～50 | 105～115 |
| PS | -40～90 | 95 | 75～100 | 240～250 |
| PET | -40～120 | 70～80 | 70～80 | 250～260 |
As can be seen from the data, PP material has the highest heat distortion temperature (100-120℃) and melting point (160-170℃) among common plastic food container materials. PP material has a very low glass transition temperature (approximately below 0℃), which means that at room temperature and hot water temperatures, its crystalline structure remains stable, and the molecular chain segments in the amorphous region also maintain rigidity, thus exhibiting excellent heat resistance.
In contrast, although PET has the highest melting point (250-260℃), its glass transition temperature (70-80℃) is a fatal weakness. Once the water temperature exceeds 70℃, the material will transform from a glassy state to a highly elastic state, causing the bottle to shrink, soften, and deform rapidly. PS material has a heat distortion temperature of 75-100℃, and begins to soften at a usage temperature of 75℃. PE material has even worse heat resistance; LDPE has a heat distortion temperature of only 40-50℃, and HDPE only 75-85℃.
2.2 Performance at High Temperatures
In actual high-temperature tests, the performance of different materials varies significantly. Research teams found through simulated experiments that when containing high-temperature foods such as braised pork (78℃) and hot and sour soup (85℃), polypropylene (PP) burger to-go boxes released approximately 12,000 microplastic particles per square centimeter within 15 minutes, while polystyrene (PS) burger to-go boxes released as many as 35,000 particles under the same conditions.
Even more worrying is that when the temperature reaches 65℃, some perfluorinated compounds released from the burger to-go boxes can directly damage the vascular endothelium, accelerating the process of arteriosclerosis. Although PP burger to-go boxes are relatively safe, they may still release harmful substances under long-term high-temperature exposure. Experiments show that polypropylene (PP) burger to-go boxes containing 70℃ hot soup can release tens of thousands of microplastic particles within 15 minutes, and these particles easily adsorb grease to form composite pollutants.
2.3 Performance Changes During Long-Term Use
Long-term use or improper heating of plastic products can lead to molecular chain rearrangement. If a food container is heated in a microwave oven beyond its heat resistance temperature, it may release plasticizers or bisphenol A.
Repeated heating can cause the container to deform, and the elasticity of the sealing strip to decrease, affecting safety. A 2024 experimental study published in *Environmental Science & Technology* showed that when plastic tableware comes into contact with hot food or hot water above 60°C, the amount of chemical substances released increases by 3-5 times compared to room temperature. A 2024 test by the Shanghai Consumer Rights Protection Committee showed that a common PP food container, after being heated five times repeatedly, released a total amount of chemical substances 2.8 times higher than during its first use, with some components approaching the limits specified in GB 4806.7-2016 "Plastic Materials and Articles for Food Contact."
III. Heat Resistance Performance in Practical Application Scenarios
3.1 Microwave Heating Scenario
In microwave heating scenarios, PP material is the only plastic food container material that can be safely used. PP material has a heat resistance temperature of 100-140°C, and can withstand the steam temperature and heat conduction generated by food during microwave heating. Even short-term heating of high-moisture foods (such as soup and porridge) will not cause softening, deformation, or release of toxic substances.
According to the national standard GB/T 18006.1-2009 "General Technical Requirements for Disposable Plastic Tableware," if a plastic food container is declared suitable for microwave heating, it should be marked with "suitable for microwave use and usage temperature." PP material has a high-temperature resistance of up to 120°C and is not easily deformed or releases harmful substances during heating.
However, it is important to note that the lids of plastic burger to-go boxes are often not made of PP material; in many cases, polyvinyl chloride (PVC) or other low-heat-resistant plastics are used. These materials may release harmful substances at high temperatures. Therefore, when using PP burger to-go boxes for microwave heating, it is recommended to remove the lid to avoid potential safety risks.
Experiments conducted by the School of Food Science at China Agricultural University showed that microwave heating of plastic burger to-go boxes with lids on can cause the internal surface temperature to locally exceed 140°C, far exceeding the material's tolerance limit.
Microwave Heating Precautions:
- Remove the lid of the food container before heating
- Control heating time to no more than 4 minutes at a time
- Avoid heating extremely hot foods with hot oil
- Do not reuse containers for long-term or repeated heating
3.2 Scenario: Containing Freshly Cooked Food
Although PP material burger to-go boxes can theoretically withstand such temperatures when containing freshly cooked food at 80-100℃, they will still release a certain amount of microplastics. Experimental data shows that PP burger to-go boxes release approximately 12,000 microplastic particles per square centimeter within 15 minutes when containing braised pork at 78℃.
PS material burger to-go boxes perform very poorly at such high temperatures. The Jinan University laboratory found that disposable foam burger to-go boxes labeled "PS6" (polystyrene) began to release long-chain alkanes, a compound that may cause inflammation and endocrine disorders, after being in contact with 100℃ boiling water for 10 minutes. The heat resistance limit of PS material is only 90℃. Once it contains hot food exceeding 90℃, it will release harmful substances such as styrene. Long-term use may damage liver and kidney function, the central nervous system, and even pose a risk of cancer.
PET material burger to-go boxes are completely unsuitable for containing high-temperature food. The heat resistance temperature of PET is generally around 70℃. It is easily deformed by heat and may release harmful substances.
To ensure safety, the following measures are recommended:
- Let freshly cooked food cool in a ceramic plate for 5 minutes until the temperature drops below 60℃ before transferring it to a plastic food container.
- Prioritize PP material burger to-go boxes (labeled "microwave-safe").
- Avoid using PS material burger to-go boxes for hot food.
3.3 Other High-Temperature Applications
Besides microwave heating and holding freshly cooked food, there are other high-temperature usage scenarios to consider:
Steaming
PP material burger to-go boxes can be directly placed in a steamer for heating because of their excellent thermal stability, which can withstand temperatures up to 120℃. However, it should be noted that the temperature during steaming may exceed 100℃, so it is recommended to choose PP burger to-go boxes labeled "suitable for steaming" and control the heating time.
High-Temperature Oily Foods
Even PP material burger to-go boxes should avoid prolonged contact with high-temperature oils. Experiments have shown that prolonged contact of PP burger to-go boxes with high-temperature oils may accelerate the release of harmful substances. Therefore, extra caution should be exercised when holding fried foods or high-temperature foods with high oil content.
Storage in high-temperature environments
In summer, the temperature inside a car can reach 70℃ under direct sunlight. Even without food, harmful substances will be slowly released from plastic burger to-go boxes. Therefore, avoid storing plastic burger to-go boxes in high-temperature environments for extended periods.
IV. Comprehensive Heat Resistance Evaluation and Usage Recommendations
4.1 Ranking of Material Heat Resistance Performance
| Ranking | Material | Heat Resistance Temperature | Characteristics | Applicable Scenarios |
| 1 | PP (Polypropylene) | 130-140℃ | The only microwave-safe material has good chemical stability | Microwave heating, holding hot food |
| 2 | HDPE (High-density polyethylene) | 110℃ | Good heat resistance, not easily decomposed | Short-term storage of hot food |
| 3 | PS (Polystyrene) | 70-90℃ | Poor heat resistance, releases harmful substances at high temperatures | Only suitable for room temperature or refrigeration |
| 4 | LDPE (Low-density polyethylene) | 70-80℃ | Poor heat resistance, easily deformed | Not suitable for high-temperature use |
| 5 | PET (Polyethylene terephthalate) | 70℃ | Worst heat resistance, easily deformed at high temperatures | Only suitable for cold drinks |
4.2 Safe Use Guidelines
Although PP material is the best choice for heat resistance, the following points should still be noted in actual use:
1. Choose the appropriate material
- Look for the "No. 5 PP" mark on the bottom
- Choose containers marked "microwave safe" or "food grade."
- Avoid using burger to-go boxes with a triangular mark of 3 (PVC) or 6 (PS) on the bottom
2. Control temperature and time
- Avoid food above 65℃ in plastic containers
- Cool hot food to below 60℃ before use
- Limit microwave heating to 3-4 minutes
3. Correct usage
- Remove the lid during microwave heating
- Avoid plastic wrap for heating
- Repeated heating is not recommended
- Avoid prolonged contact with high-temperature oily foods
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4. Pay attention to special circumstances
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Even PP material may release harmful substances under extreme conditions
The release of microplastics increases at high temperatures
Long-term use may have health effects
4.3 Consideration of Special Materials
In addition to the common PP, PS, PET, and PE materials, some special materials are worth noting:
Crystalline PET (CPET)
Crystallized PET The heat distortion temperature of this material can reach 196℃, and it can maintain its shape at temperatures below 180℃. It can be used to hold hot food and is suitable for making burger to-go boxes that require high-temperature resistance, such as lunch boxes, bowls, plates, and cups. However, this material is not common in disposable burger to-go boxes.
Melamine resin (MF)
Melamine tableware, also known as imitation porcelain tableware, can withstand temperatures up to 110-130℃. However, melamine tableware is easily deformed at high temperatures and cannot be used in microwave ovens or ovens. It should not be scrubbed with steel wool. If wear, cracks, or discoloration occur, it should be replaced promptly.
Polycarbonate (PC)
PC material has a heat resistance temperature of 120-130℃, but due to the potential release of bisphenol A, it has been gradually replaced by other materials. According to national standards, PC material is not allowed to be used in the production of infant feeding bottles.
V. Summary
Polypropylene (PP) is undoubtedly the best choice for heat resistance in disposable plastic burger to-go boxes, with a heat distortion temperature as high as 120-140℃. It is the most heat-resistant of all commonly used plastics and can withstand microwave heating and high-temperature food requirements.
However, even PP material will release harmful substances at extremely high temperatures (90-100℃). Therefore, rational use is essential - control temperature and time to ensure safety. Prioritize PP containers marked with "No. 5" and cool extremely hot food to below 60℃ before use.
With technological advancements, new heat-resistant materials may emerge, but under current conditions, PP remains the best choice for overall heat resistance, meeting the needs of most high-temperature usage scenarios.
