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中文简体I. Overview of PP Tableware Materials
PP tableware is a type of disposable plastic tableware made primarily from polypropylene (PP). PP is a semi-crystalline thermoplastic polymer characterized by low density, excellent toughness, non-toxicity, odorlessness, and ease of processing and molding. Compared to materials like PS (polystyrene) and PET (polyethylene terephthalate), PP offers significant advantages in heat resistance and chemical stability, making it widely used in tableware, food packaging, and medical supplies.
II. Upper Heat Resistance Temperature of PP Tableware
The heat resistance of PP tableware depends on the crystallinity, molecular structure, additive types, and processing technology of the polypropylene. While the melting point of polypropylene is generally around 160°C, its actual heat-resistant operating temperature is slightly lower, typically between 100°C and 120°C.
Even in short-term high-temperature environments (such as hot water brewing or steam exposure), PP tableware maintains structural stability and resists deformation or release of harmful substances. Therefore, it is often used in hot drink cup lids, microwaveable containers, and takeout tableware.
1. Heat Resistance of Homopolymer PP
Homopolymer PP has a highly regular molecular structure and high crystallinity, resulting in excellent heat resistance. This type of PP tableware can withstand temperatures of approximately 110°C to 130°C, making it suitable for hot water, oily foods, and short-term microwave heating.
When used at high temperatures, the Vicat softening point of homopolymer PP tableware can reach around 125°C. However, prolonged exposure to high temperatures can cause slight warping or degradation, affecting its appearance and service life.
2. Heat Resistance of Copolymer PP
Copolymer PP incorporates ethylene monomers into the molecular chain to improve impact strength and low-temperature toughness. However, the crystallinity of the copolymerized polypropylene decreases, resulting in a slightly lower heat resistance temperature. The upper heat resistance limit is generally between 100°C and 110°C.
This material is often used in products requiring both toughness and formability, such as disposable cutlery, forks, and spoons, and takeout containers. Although its heat resistance is slightly lower, it remains safe and stable within the actual food contact temperature range.
3. High-Temperature Modified PP
To meet the demands of higher-temperature food packaging, some manufacturers add heat-resistant modifiers to the PP base material or increase the heat distortion temperature by blending it with inorganic fillers such as nylon and talc. Modified PP tableware can be used for short periods in environments between 130°C and 150°C, making it suitable for microwave heating and high-temperature sterilization.
3. Low-Temperature Brittleness Temperature of PP Tableware
The low-temperature brittleness temperature is an important indicator of the impact resistance of polypropylene. When the temperature falls below a certain critical point, the mobility of the PP molecular chains decreases significantly, and the material transitions from a ductile state to a brittle state, making it susceptible to breakage or fracture.
1. Low-Temperature Brittleness Temperature of Homopolymer PP
Homopolymer PP has weak low-temperature impact resistance, with a low-temperature brittleness temperature generally ranging from -5°C to 0°C. When the ambient temperature falls below this range, PP tableware is prone to cracking and breaking under external forces. Therefore, prolonged storage of homopolymer PP tableware in a frozen environment is not recommended.
2. The Low-Temperature Toughness Advantage of Copolymer PP
The introduction of ethylene-propylene copolymer has effectively improved the low-temperature performance of polypropylene. The low-temperature brittleness temperature of copolymer PP tableware can be reduced to -20°C to -30°C. This material is widely used in cold chain packaging, cold beverage containers, and refrigerated distribution, maintaining excellent impact toughness and shape stability at low temperatures.
3. Other Factors Affecting Low-Temperature Performance
The low-temperature brittleness temperature is affected not only by the molecular structure but also by product thickness, filler type, crystal orientation, and processing cooling rate. Thick-walled PP products tend to retain some toughness at low temperatures, while thin-walled products experience more pronounced brittleness due to internal stress concentration.
In addition, while talc or glass fiber reinforcement improves rigidity and heat resistance, it may reduce low-temperature impact resistance. Therefore, a balance between heat resistance and toughness must be struck during the design phase.
IV. Actual Application Temperature Range
A comprehensive analysis of the thermal properties of different types of PP tableware indicates that the safe operating temperature range is generally -20°C to 120°C.
Below -20°C, some PP products may be at risk of brittle cracking;
Above 120°C, they may soften, deform, or experience performance degradation.
Therefore, in the food service and packaging industries, PP tableware is widely considered an ideal material that combines heat resistance and safety, suitable for a variety of applications, including hot and cold drink containers, lunch boxes, soup bowls, and takeout packaging.
