Do You Know All about The Process of Rubber Making?

Rubber products occupy an irreplaceable position in modern industry due to their excellent elasticity and durability. However, with the expansion of application areas, the safety performance requirements for rubber products are increasing, especially the flame retardant performance. This paper will focus on the basic process flow of rubber manufacturing and discuss the application of flame retardants in rubber production.

1. Basic Process Flow

There are many kinds of rubber products, but the production process is basically the same. The basic process of rubber products with general solid rubber - raw rubber as raw material, including six basic processes: plasticizing, mixing, calendering, pressing out, molding, vulcanization. Of course, raw material preparation, finished product finishing, inspection and packaging and other basic processes are also less.

The processing of rubber is mainly a process to solve the contradiction between plasticity and elasticity. Through a variety of process means, make the elastic rubber into plastic plastic rubber, and then add a variety of matching agent made of semi-finished products, and then through the vulcanization of semi-finished products with plasticity into high elasticity, good physical and mechanical properties of the rubber products.

2. Preparation of raw materials

I. The main raw material of rubber products is based on raw rubber as the basic material, raw rubber is grown in the tropics, subtropics, rubber trees, through the artificial cut open the bark collection.

II. A variety of compatibilizers, is to improve some of the properties of rubber products and the addition of auxiliary materials. Including the addition of flame retardants to improve the fire retardant properties of rubber.

III. materials (cotton, linen, wool and a variety of man-made fibers, synthetic fibers and metal materials, steel wire) is used as the skeleton material of rubber products to enhance mechanical strength, limit product deformation. Ingredients must be weighed accurately according to the formula during raw material preparation.

IV. In order to make the raw rubber and mating agent can be mixed evenly with each other, the material needs to be processed. Raw rubber should be baked at 60℃-70℃ in the drying room and then cut rubber, broken rubber into small pieces, with the agent has a block, such as paraffin, stearic acid, rosin, etc. to be crushed; powdered if it contains mechanical impurities or coarse particles need to be screened to remove; liquid, such as pine tar, gumarone need to be heated, melting, evaporation of water, filtering impurities, the with the agent to be dried or easy to caking, mixing, if you can not be dispersed uniformly, the sulfurization will affect the quality of the product. If it can't be dispersed evenly during mixing, it will affect the product quality when vulcanizing.

3. Plasticizing

Raw rubber is full of elasticity, lack of plasticity necessary for processing, so it is not easy to process. In order to improve its plasticity, the raw rubber should be plasticized, so that in the mixing with the agent will be easy to uniformly dispersed in the raw rubber, and at the same time in the calendering, molding process will also help to improve the permeability of the rubber material, penetrate into the fiber fabric and molding fluidity. The process of degrading the long-chain molecules of raw rubber to form plasticity is called plasticizing.

Raw rubber plasticizing methods are mechanical plasticizing and thermal plasticizing two kinds. Mechanical plasticizing is not too high temperature through the plasticizer mechanical extrusion and friction to make the long-chain rubber molecules degraded short by the highly elastic state into a plastic state. Thermoplasticizing is to the raw rubber into the burning hot compressed air, under the action of heat and oxygen to make the long-chain molecules degradation shorten so as to obtain plasticity.

4. Mixing

In order to adapt to a variety of different conditions of use, to obtain a variety of different properties, but also in order to improve the performance of rubber products and reduce costs, it is necessary to add different matching agents in the raw rubber. Mixing is the plasticization of the raw rubber and with the agent mixture, put in the refining machine through the mechanical mixing effect so that the agent completely and evenly dispersed in the raw rubber in a process. In this step, according to the specific needs of rubber products, flame retardants, such as antimony trioxide, etc., will be added to improve the flame retardant properties of rubber.

Mixing is an important process in the production of rubber products, if the mixing is not homogeneous, it will not give full play to the role of rubber and cooperating agent, thus affecting the performance of the product. The rubber obtained after mixing is called compounding rubber, which is a semi-finished material for manufacturing various rubber products, commonly known as rubber. Usually sold as a commodity, the buyer can use the rubber material directly processing molding, vulcanization to make the required rubber products. According to the different formulations, the rubber mix has a series of different properties of different grades and varieties to choose from.

5. Molding

In the production of rubber products in the process of using the calender or press out of the machine, made in advance of the shape of a variety of different sizes of the process is called molding. There are three types of molding methods as follows:

I. Calendering

It is suitable for manufacturing simple sheet and plate products. It is the mixing of rubber through the calender pressed into a certain shape, a certain size of the film, this method is called calender molding. Some rubber products, such as tires, rubber cloth, hoses and other textile fibers used in the material must be coated with a thin layer of rubber, in the fiber coated with rubber is also known as sticker or rubbing rubber. Gluing process is generally also completed on the calender. Fiber materials in the calender before the need for drying and soaking, drying is designed to reduce the water content of fiber materials, so as to avoid evaporation of water blistering and improve the temperature of the fiber materials to ensure the quality of the calendering process. Gluing is a necessary process before hanging the glue, in order to improve the bonding properties of the fiber material and the glue.

II.Pressing out molding

Used for more complex rubber products, such as tire treads, hoses, wire surface covering rubber, need to be manufactured by the method of extrusion molding. It is the plasticity of the rubber mix into the hopper of the extruder, under the extrusion of the screw through a variety of mouth shape. Before pressing out the rubber material must be preheated, so that the rubber material is soft, easy to extrude to get a smooth surface, accurate size of the rubber products.

III. Molding

Molding method can be used to manufacture certain complex shapes of rubber products, such as leather bowls, seals and so on. With the help of molding Yin, Yang mold will be placed in the mold heating rubber molding.

6. Vulcanization

Plastic rubber into elastic rubber process is called vulcanization, it is a certain amount of vulcanizing agent, such as sulfur, vulcanization accelerator, etc. added to the semi-finished products made of raw rubber, in the vulcanizing tank at the specified temperature heating, insulation, so that the linear molecules of raw rubber through the generation of "sulfur bridges" and cross-linking each other to form a solid mesh structure, thus making the plastic rubber into a plastic rubber. Thus, the plastic rubber material becomes a vulcanized rubber with high elasticity. Because the crosslinking bond is mainly composed of sulfur, so it is called "vulcanization". In this process, the presence of flame retardants helps to improve the thermal stability and flame retardant properties of the rubber.

With the rapid development of synthetic rubber, there are now many varieties of vulcanizing agents, including organic polysulfides, peroxides, metal oxides, etc. in addition to sulfur. Therefore, all can make the linear structure of plastic rubber into a three-dimensional network structure of elastic rubber process are called vulcanization. Where the rubber material can play a "bridge" role in the material are called "vulcanizing agent". Vulcanized elastic rubber is called vulcanized rubber is also called soft rubber, commonly known as "rubber". Vulcanization is one of the most important processes of rubber processing, a variety of rubber products must be vulcanized to obtain the desired performance.

Unvulcanized rubber in the use of the use of value, but the lack of sulfur (vulcanization degree is not enough, vulcanization time is not enough to achieve the best state) and over-sulfur (vulcanization time more than the performance of a significant decline) are to make the rubber performance decline. So the production process must strictly control the vulcanization time, in order to ensure that the vulcanized rubber products have the best performance and the longest service life.

7. Auxiliary measures

In order to achieve the use of performance should also be added in the production process of auxiliary measures:

Increase strength - with hard carbon black mixed with phenolic resin

Increase wear resistance - with hard carbon black

High air tightness requirements - less use of high volatility components

Increase heat resistance - using new vulcanization process

Increase cold resistance--reduce the crystallization tendency through the debranching inlay of raw rubber, use plasticizer with low temperature resistance.

Increase the flame resistance - do not use flammable additives, less use of softeners, the use of flame retardants such as antimony trioxide

Increase oxygen and ozone resistance - use p-diamine protective agent.

Improvement of electrical insulation - with high structural fillers or metal powder, with antistatic agents

Improve the magnetic property--using strontium ferrite powder, alnico iron powder, barium iron powder as filler.

Improvement of water resistance - lead oxide or resin vulcanization system, with low water absorption fillers such as barium sulfate, clay.

Improve oil resistance - full cross-linking, less plasticizers

Improve acid and alkali resistance--use more fillers.

Improve the high vacuum property--use additives with low volatility.

Conclusion

With the continuous expansion of the application field of rubber products, the requirements for the flame retardant performance of rubber are getting higher and higher. By rationally applying flame retardants in the rubber production process, not only the safety of rubber products can be improved, but also the demand for high-performance rubber in specific industries can be met. The continuous optimization and innovation of the rubber process provides unlimited possibilities for the future development of rubber products.

Guangzhou Yinsu Flame Retardant New Material Co., Ltd.

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