Overview of Rubber vulcanization System and vulcanization process

Rubber vulcanization is an important link in the production process of rubber products and also a key step to endow rubber materials with excellent physical and mechanical properties. This article will provide a detailed introduction to the basic composition and classification of the rubber vulcanization system, as well as the specific stages and principles of the vulcanization process, to help readers better understand this complex and important technological process.

I. Overview of Rubber Vulcanization System

The rubber vulcanization system is mainly composed of vulcanizing agents, accelerators, activators and anti-scorching agents, etc. These components interact with each other during the vulcanization process, triggering cross-linking reactions of rubber molecular chains, thereby forming a stable three-dimensional network structure. The selection and proportion of the vulcanization system directly affect the performance and quality of rubber products.

According to the different vulcanizing agents, rubber vulcanization systems can be divided into two major categories: sulfur vulcanization systems and non-sulfur vulcanization systems. The sulfur vulcanization system is the most commonly used vulcanization system in the rubber industry, mainly for the vulcanization of unsaturated olefin rubber. It can be further subdivided into conventional vulcanization systems, effective vulcanization systems and semi-effective vulcanization systems, etc. Non-sulfur vulcanization systems include peroxide vulcanization systems, resin vulcanization systems, etc., and are suitable for specific types of rubber products.

Ii. Detailed Explanation of Vulcanization Process

The rubber vulcanization process is a complex chemical reaction process, which can usually be divided into the following stages:

1. Induction stage (scorch stage) :

At this stage, vulcanizing agents, accelerators and activators begin to interact with each other, gradually activating the rubber molecular chains. At this point, the rubber compound maintains good fluidity, but large-scale cross-linking has not yet begun. The duration of this stage is called scorch time, which determines the safety of the rubber compound during the processing.

2. Crosslinking reaction stage (hot vulcanization stage) :

As the temperature rises, the rubber molecular chains begin to undergo cross-linking reactions with the vulcanizing agent, generating cross-linking bonds. During this stage, the elasticity and tensile strength of rubber increase sharply, and the vulcanization reaction rate gradually accelerates. The speed of the crosslinking reaction mainly depends on the type and dosage of the accelerator and the vulcanization temperature.

3. Network formation stage (flat sulfation stage) :

The cross-linking reaction tends to be completed, and a stable three-dimensional network structure is formed between the rubber molecular chains. At this point, the physical and mechanical properties of rubber reach the optimal state, and the tensile strength, hardness and other properties are significantly improved. This stage is called the flat vulcanization stage because the performance changes of rubber are relatively gentle.

4. Overvulcanization stage:

If the vulcanization time continues to be prolonged, the cross-linking bonds between the rubber molecular chains will undergo rearrangement and cracking reactions, resulting in a decline in rubber performance. This stage is called the overvulcanization stage and should be avoided as much as possible.

Iii. Performance Changes during vulcanization

During the vulcanization process of rubber, its physical and mechanical properties will undergo significant changes. Take natural rubber as an example. As the degree of vulcanization increases, the properties of rubber such as elasticity, tensile strength, elongation at a given length, tear strength and hardness will all improve. However, properties such as elongation, compression set and fatigue heat generation will decrease. In addition, the air permeability and water permeability of rubber decrease, while its heat resistance and chemical stability increase.

Iv. Selection of Vulcanization Conditions

Vulcanization conditions include vulcanization temperature, vulcanization pressure and vulcanization time, which have a significant impact on the vulcanization effect. The level of vulcanization temperature directly affects the vulcanization speed and product quality, and is usually determined based on factors such as the type of rubber, vulcanization system and product structure. Vulcanization pressure helps to enhance the compactness of the rubber compound and the adhesion between the layers. The control of vulcanization time is related to the final performance of rubber products and requires comprehensive consideration of factors such as the properties of raw rubber, vulcanization system and compounding agents.

Summary

Rubber vulcanization is an important process in the production of rubber products. It endows rubber materials with excellent physical and mechanical properties through complex chemical reactions. Understanding the basic composition of the rubber vulcanization system and the specific stages of the vulcanization process is of great significance for optimizing the vulcanization process and improving product quality. With the advancement of technology and the continuous improvement of processes, rubber vulcanization technology will also keep developing and perfecting.

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