TPE| Will film-grade TPR material crack under low temperature conditions?

Film-grade TPR materials are widely used in packaging, daily necessities, and electronic protection due to their excellent flexibility and ease of processing. However, when these materials are used in low-temperature environments, such as refrigerated packaging or outdoor applications, many users worry about whether the film will become brittle or even crack at low temperatures. Whether film-grade TPR materials are susceptible to cracking at low temperatures is not a fixed answer. It is influenced by many factors, including the material formulation, the degree of low temperature, and the operating conditions. It's not a simple yes or no. Let's take a look at the analysis by Huizhou Zhongsuwang.

1. Understanding the Basic Low-Temperature Properties of Film-Grade TPR Materials

TPR materials, also known as thermoplastic elastomers, combine the elasticity of rubber with the processability of plastic. Their low-temperature performance is primarily determined by their glass transition temperature, commonly denoted by Tg. When the ambient temperature falls below the Tg of the material, TPR material gradually transitions from a flexible, elastic state to a hard, brittle, glassy state. This significantly reduces the material's flexibility, making it susceptible to cracking or even fracture when subjected to external impact or bending. If the temperature is above the Tg, the material maintains good elasticity and flexibility.

For film-grade TPR materials, the Tg of most common products in the industry ranges from several dozen degrees below zero to 0°C. This means that in everyday low-temperature environments, such as indoor winter or in standard refrigerated storage environments, where temperatures are generally above 0°C, the material generally maintains flexibility and is less susceptible to brittle cracking. However, in extreme low-temperature environments, such as freezers or in freezing weather in northern China, where temperatures may drop to low levels, and the material's Tg is relatively high, it may enter the glassy state, increasing the risk of brittle cracking.

II. Key Factors Affecting Low-Temperature Brittle Cracking of Film-Grade TPR Materials

1. Material Formulation: The Fundamental Factor Determining Low-Temperature Performance

The type and content of the soft segment components in the formulation of film-grade TPR materials directly influences its resistance to low-temperature brittle cracking. Common soft segment components include polyether and polyester.

Using a soft segment with a lower Tg, such as a polyether-based soft segment, and a high soft segment content will improve the material's low-temperature flexibility, maintaining elasticity at lower temperatures and reducing the risk of brittle cracking.

If the soft segment is of a higher Tg, such as some polyester-based soft segments, or if the hard segment content is too high (common hard segments include polystyrene), the material's Tg will increase, making it more susceptible to hardening and brittle cracking at low temperatures.

In addition, the inclusion of a low-temperature toughening agent in the formulation can also have an impact. An appropriate amount of toughening agent can lower the material's Tg, improve low-temperature impact resistance, and further reduce the risk of brittle cracking.

2. Low-Temperature and Exposure Duration: The colder the temperature and the longer the exposure, the higher the risk.

Even film-grade TPR materials with excellent low-temperature performance can become hard and brittle if exposed to extreme temperatures far beyond their tolerance range for extended periods due to slowed molecular motion and loss of elastic recovery. Furthermore, the longer the material is exposed to low temperatures, the more stress accumulates within the material. This increases the likelihood of brittle cracking if subjected to even the slightest external force, such as stretching, bending, or impact.

3. Film Thickness and External Force: Thin Films Are More Susceptible

The thickness of thin-film TPR materials also affects low-temperature brittle cracking. Thinner films have weaker impact resistance at low temperatures and are more susceptible to cracking than thicker films when subjected to external forces such as stretching and rubbing. Thick films, however, have a more stable structure and can, to a certain extent, buffer external forces, reducing the risk of brittle cracking.

3. How to Prevent Low-Temperature Brittle Cracking of Thin-Film TPR Materials? If you need to use film-grade TPR materials in low-temperature environments, there are two key considerations:

When selecting a material, pay attention to the material's low-temperature performance parameters. Prioritize products clearly labeled as low-temperature brittle crack resistant and with a low Tg. Verify that the recommended operating temperature range covers the intended application. For example, for materials used in freezing environments, choose a material with a lower Tg.

Control usage conditions and minimize prolonged exposure of the film to extreme low temperatures. If low-temperature transportation or storage is required, protective packaging can be employed, such as adding insulation film to the outer layer to minimize direct contact with the low-temperature environment. Avoid aggressive bending or stretching of the film at low temperatures.

In short, while film-grade TPR materials may experience brittle cracking in low-temperature environments, this is not guaranteed. The key lies in the material's inherent low-temperature performance, which is primarily determined by the formulation, the specific temperature of the low-temperature environment, and whether the material is subjected to external forces. By selecting products suitable for low-temperature performance based on the intended application and properly controlling usage conditions, you can effectively reduce the risk of brittle cracking and ensure that film-grade TPR materials perform stably in low-temperature environments.