Rubber formulations can be divided into experimental formulations and practical formulations according to their uses

The rubber formulation is generally composed of raw rubber, vulcanized antioxidant reinforcement system, protection system, reinforcement system and softening system. The purpose of formula design is to seek the best ratio combination of various components, so as to obtain good comprehensive performance. The formulation design will ultimately achieve the following objectives:

1. Meet the performance requirements of the sealing ring.

2. The rubber material processing technology has good performance.

3. Under the premise of ensuring product quality, try to choose raw materials with low price, rich sources, or low toxicity and stable performance.

Rubber formulations can be divided into experimental formulations and practical formulations according to their uses. The former is to study or identify the relationship between a certain raw material and the properties of vulcanized rubber and compound rubber, and strive to be simple in composition. The practical formula mainly studies the relationship between the properties of the vulcanizate and the actual performance of the product and the technological properties of the compounded rubber. The formulation process of the practical formula is as follows:

Environmental conditions and manufacturing process analysis of product use - à selection of rubber species and various compounding agents that make up the formula to form test formula - à performance evaluation test - à component adjustment and improvement - à expansion test to determine the practical formula.

<2> O-ring sealant compound formulation design

The working environment of O-ring rubber sealing ring is complex and diverse, and its rubber material is required to have some special properties. In the hydraulic system, it is required to have good oil resistance, temperature resistance, low compression deformation and certain tensile strength. As a dynamic seal, in addition to the requirements, the rubber compound should also have good abrasion resistance and tear resistance. Sealing for special media requires less volume change and hardness change of the compound in the medium. In short, the formula design should be comprehensively considered according to specific working conditions, medium types, use temperature, working pressure and application state.

〈3〉 O-ring sealant processing

At present, the production method of O-shaped rubber sealing ring is mainly produced by over-molding method. Among them, the vulcanization methods of molded products mainly include flat molding, transfer molding and injection molding. Flat molding has a long history. Transfer molding began to be used around the 1950s, while injection molding has gradually entered the rubber industry from the plastics industry since the 1960s. The current development trend is to gradually develop the injection pressure method, but due to the different ranges of adaptation. The coexistence and development of the three is still a reality. According to its characteristics, the O-ring still uses flat molding as the main molding method.

In the process of molding vulcanization, it is necessary to strictly and correctly grasp the temperature, time and pressure of vulcanization, and pay attention to the changes of temperature and other parameters during the vulcanization process at any time, and carry out corresponding treatment, otherwise the product will be under-sulfur or over-sulfur. If an automatic control system is used, the entire vulcanization process will be automatically recorded and controlled to ensure that the product reaches a positive vulcanization level.

The vulcanization temperature is one of the basic conditions for the vulcanization reaction of the rubber O-ring, which directly affects the vulcanization speed and product quality. High vulcanization temperature, fast vulcanization speed, and high production efficiency; low vulcanization temperature, slow vulcanization speed. The vulcanization temperature is formulation dependent, and importantly depends on the type of rubber and the vulcanization system used. The suitable vulcanization temperature for natural rubber is generally 143℃--150℃, and for synthetic rubber, it is generally 150℃～180℃. The vulcanization time is usually determined by the test according to the determined vulcanization temperature.

The purpose of pressurizing rubber products during the vulcanization process is to make the rubber material flow easily, fill the cavity, prevent the generation of air bubbles during the vulcanization process, and improve the compactness of the product. The size of the vulcanization pressure depends on the hardness of the rubber compound and the size of the mold. When the hardness of the rubber compound is high and the size of the mold is large, the pressure can be larger, otherwise, the pressure should be appropriately reduced.