With the continuous expansion of the industrial field, especially the increasing demand for applications in extreme environments such as high temperature and high pressure, the importance of developing high-temperature resistant rubber materials has become increasingly prominent. Under high temperature conditions, the physical and chemical properties of rubber materials undergo significant changes, such as thermal aging, compression set, and performance degradation. In order to improve the high temperature resistance of rubber, it is necessary to start with formula design, optimize the composition and processing technology of rubber materials. This article will explore how to enhance the high temperature resistance of rubber by adjusting various components in the formula.

1、 Factors affecting the high temperature resistance of rubber

The high temperature resistance of rubber refers to its ability to maintain its original properties in high temperature environments. The factors that affect this performance mainly include the following aspects:

molecular structure

The molecular chain length, crosslinking density, and crosslinking method of rubber have a direct impact on its high temperature resistance. A higher crosslinking density can significantly improve the heat resistance of rubber, but excessive crosslinking may cause the material to become brittle.

Formula ingredients

Various additives, fillers, and crosslinking agents added to the formula can be optimized to improve the high temperature resistance of rubber.

curing system

Vulcanization is a key step in optimizing rubber properties, and the selection and conditions of the vulcanization system are crucial for improving high temperature resistance.

external environment

Environmental factors such as temperature, humidity, oxygen, and ozone work together to affect the aging process of rubber materials, which in turn affects their high temperature resistance.

2、 Formula optimization strategy for improving the high temperature resistance of rubber

In order to improve the high temperature resistance of rubber, formula design should focus on the following aspects:

（1） Choose high temperature resistant rubber base material

Different types of rubber base materials have different high temperature resistance properties. When optimizing the rubber formula, the appropriate rubber base material should be selected according to the usage environment:

Fluororubber (FKM): Fluororubber is one of the excellent materials for high temperature resistance and chemical corrosion resistance, capable of withstanding working temperatures up to about 250 ° C, and suitable for high-temperature sealing, shock absorption, and anti-corrosion scenarios. However, it has high brittleness and poor resilience.

Silicone rubber (VMQ): Silicone rubber has good high temperature resistance and can work stably in the temperature range of -50 ° C to 230 ° C. It is commonly used in high-temperature seals, molds, and gaskets. Although it has excellent high temperature resistance, its mechanical properties are relatively weak and need to be optimized through fillers.

Nitrile rubber (NBR): Nitrile rubber is known for its oil resistance, but it can also maintain certain properties in high temperature environments by adding heat-resistant oxygen agents and increasing cross-linking density. It performs well under high temperature and pressure conditions in the petrochemical industry.

Polyurethane rubber (PU): Polyurethane rubber performs well in high temperature resistance, wear resistance, and oil resistance, and is commonly used in components such as transmission belts and sealing rings under high temperature conditions.

（2） Choose high-temperature resistant fillers

The selection of fillers is crucial for improving the high temperature resistance of rubber. Common high-temperature resistant fillers include:

Silicone: As a high-temperature resistant filler, silicone has excellent high-temperature resistance, which can improve the thermal stability of rubber without affecting its elasticity. Its addition amount is usually between 5% and 20%, which can significantly improve the performance of rubber at high temperatures.

Carbon black: Carbon black not only enhances the strength of rubber, but also improves its high temperature resistance. When used in conjunction with other high-temperature resistant fillers, carbon black can effectively enhance the wear resistance, oxidation resistance, and thermal stability of rubber.

Bauxite: Bauxite is a high-temperature reinforcing filler that can significantly improve the heat resistance and thermal stability of rubber. It has good stability at high temperatures and is commonly used in the formulation design of high-temperature sealing materials.

Ceramic particles: Ceramic particles have excellent heat resistance and can be added as fillers to rubber to enhance its high temperature resistance, while also increasing the hardness and tensile strength of the material.

（3） Optimize crosslinking system

The structure of the cross-linked network determines the high temperature resistance of rubber. By increasing the cross-linking density, the thermal stability and high temperature resistance of rubber molecular chains are enhanced. Common crosslinking methods include:

Sulfur crosslinking: Sulfur is the most commonly used crosslinking agent, which can effectively improve the high temperature resistance of rubber. Increasing the amount of sulfur appropriately can improve the crosslinking density and enhance the durability of rubber at high temperatures. However, excessive sulfur cross-linking may cause rubber to become brittle and should be used with caution.

Peroxide crosslinking: The peroxide crosslinking system has better stability at high temperatures and is suitable for rubber materials that require high temperature resistance. The crosslinking process can maintain a stable structure at higher temperatures, but the cost is high and requires precise control.

Radiation crosslinking: Radiation crosslinking is a crosslinking method achieved through radiation energy, suitable for certain special types of rubber. By radiation crosslinking, a higher crosslinking density can be obtained at lower temperatures, thereby improving high temperature resistance.

（4） Add anti-aging agents and antioxidants

Oxidation is one of the main causes of rubber aging in high-temperature environments. To improve the high-temperature aging resistance of rubber, anti aging agents and antioxidants can be added to the formula. These additives can effectively delay the oxidation process of rubber at high temperatures and maintain its physical and chemical properties:

Antioxidants: Commonly used antioxidants include hindered amine, benzotriazole, and diene antioxidants. These antioxidants can effectively reduce the erosion of rubber by oxidation and prolong its service life.

Anti aging agents: The function of anti aging agents is to enhance the rubber's resistance to high temperatures. Commonly used ones include olefins and phosphates. These additives can slow down the thermal degradation reaction of rubber and maintain its stability in high-temperature environments.

（5） Adjust vulcanization conditions

The vulcanization conditions are crucial for the high temperature resistance of rubber. Properly adjusting the vulcanization temperature and time can effectively improve the thermal stability and anti-aging properties of rubber. The optimization of vulcanization temperature and time is as follows:

Vulcanization temperature: High temperature helps to enhance the cross-linking density of rubber, and the suitable vulcanization temperature is usually between 160 ° C and 180 ° C. Excessive temperature may lead to uneven cross-linking and affect the elasticity of rubber.

Sulfurization time: Prolonged vulcanization time may cause the rubber surface to harden and lose some elasticity. Generally speaking, the vulcanization time is controlled within 10-30 minutes to ensure sufficient cross-linking and prevent excessive vulcanization.

conclusion

Improving the high temperature resistance of rubber requires comprehensive optimization from multiple aspects such as rubber base materials, fillers, cross-linking systems, additives, and vulcanization processes. By scientifically designing formulas and adjusting production processes, the stability and service life of rubber under high temperature conditions can be effectively improved. In the future, with the increasing demand for high-performance rubber materials, the optimization of high-temperature resistant rubber formulations will continue to innovate, driving the rubber industry towards higher performance standards.