What is the temperature range of food paper boxes

Food paper boxes play a key role in the modern food industry. Their temperature resistance is no longer a single performance factor; it encompasses a temperature range determined by the paper base material, barrier coating, and specific processing techniques.

Low-Temperature Resistance: Refrigeration and Cold Chain Logistics

In the cold chain logistics and frozen food sectors, food paper boxes must withstand extremely low temperatures, down to -18°C or even -40°C.

1. Brittleness Resistance and Fiber Structure

Ordinary paperboard loses its toughness and becomes brittle in low-temperature environments, easily cracking and causing packaging damage and freezer burn.

Specialty Fiber Selection: Manufacturers use virgin fiber or specially treated long fibers to ensure that the paperboard maintains high flexibility and structural integrity even at low temperatures.

Cold-Resistant Coating: Barrier layers such as HDPE (high-density polyethylene) or modified PP (polypropylene) are used. These materials maintain excellent performance at low temperatures, preventing shrinkage and separation of the coating from the paperboard. Furthermore, special sizing agents and moisture-resistant coatings protect against condensation and moisture intrusion during freezing and thawing.

Scope of Expertise: Food paper boxes for frozen foods are typically designed to withstand temperatures as low as −40°C (−40°F), ensuring safety during deep freezing and transportation.

Hot Food Insulation: Basic Heat Resistance

For hot food storage in fast food, takeout, and foodservice, paper boxes require basic heat resistance and insulation.

1. Temperature Limits of the Base Polymer Liner

PE (Polyethylene) Coating: The most common liner material. Standard LDPE (Low-Density Polyethylene) coatings typically have a temperature limit of around 90°C to 110°C (90°F to 110°C). It can safely withstand the temperature of freshly fried, non-fried foods (such as rice and noodles), but is not suitable for prolonged contact with fried or extremely hot foods, and is not suitable for microwave heating, as the high temperatures may soften or decompose the PE.

High-Melting-Point PP Coating: To meet higher temperature requirements, such as freshly fried French fries, hamburgers, or hot soups, a polypropylene (PP) coating is used. PP has a higher melting point and a heat resistance of 120°C to 150°C, providing improved oil resistance and heat stability, making it a preferred lining material for microwave-safe paper boxes.

Scope of Application: The safe storage temperature of basic hot food boxes is typically limited to below 110°C.

High-Temperature Processing Applications: Microwave and Oven Compatibility

The highest level of temperature resistance requires that food paper boxes be directly suitable for microwave heating or conventional oven baking, which requires complex composite structural design.

1. Microwave-Safe Boxes

Microwave heating requires packaging to withstand the rapid temperature rise of the food inside within a short period of time.

PP/PET composite lining: PP is the de facto standard for microwave-safe box linings due to its high heat resistance (typically >120°C). Some high-end applications also use PET (polyethylene terephthalate) coatings, which offer even better heat resistance than PE, but typically still require specialized ovenability testing.

Safe Adhesives: High-temperature food-grade adhesives must be used at the bonding points of the box to prevent debonding during heating and ensure leak resistance.

2. Ovenable Paperboard

Oven-safe paperboard is the ultimate benchmark for heat resistance.

CARDBOARD + PP Composite Technology: This technology utilizes heat-resistant cardboard laminated with specialized ovenable PP or high-crystallinity PET, enabling cartons to withstand the dry heat of conventional ovens.

Professional Temperature Range: These cartons can typically withstand baking temperatures of +200°C or even +220°C for 20-30 minutes. These products are primarily used for "bake-in-box" or ready-to-cook" prepared food packaging.