The white carbon black has decomposition or adsorption effect on the accelerator, and the addition of the surfactant can reduce the decomposition and adsorption of the white carbon black to the accelerator. The reinforcing effect of the white carbon black mainly depends on the amount of binding gel formed by the action of the white carbon black and the rubber. However, most of these phenomena are usually completed during mixing, which depends on two prerequisites, temperature and time. When doing rubber test and sampling, sometimes it is operated in a very short time and at a lower temperature, even if no surfactant is added, a satisfactory sulfur curve can be obtained, even if the positive vulcanization time is ensured, the sample is still It will feel a similar phenomenon of severe sulfur. In fact, it is not under-sulfur, but the presence of a large number of polar hydrophilic groups, which makes the rubber and white carbon black have poor affinity, plus lower temperature and shorter time. It is difficult for the silica to adsorb the promoter in a large amount, so that the complete vulcanization curve can still be exhibited. However, it is more difficult to generate a certain amount of silica-binding gel. It is difficult to wet each other between rubber and silica, and the contact surface between silica and rubber is smaller, so that the white carbon black loses its reinforcing properties. .
In the white carbon black compound formulation, the basic alcohol or amine active agent can be neutralized as the silane coupling agent to neutralize the acidic (hydrophilic) silanol group, and the white carbon black is used as the surface. The role of reason. However, the difference is that the polyol active agent is also an activator of the accelerator, especially the thiazole accelerator. As the amount of the activator increases, the scorch time and the vulcanization time of the compound are significantly shortened. The mechanism of action is mainly to increase the activation energy of the accelerator and reduce the critical activation temperature of the accelerator. It is reasonable to say that the optimum amount of surface treatment with the activator is often determined by the content of the surface active group of the silica, but When the surfactant is used alone in the formulation, it is generally first to satisfy the optimum activation energy of the sulfide, and it is difficult to balance the optimum surface treatment agent as a modifier. Its role is a surface treatment. The modification effect is obviously inferior to that of the silane coupling agent. However, when the surfactant is treated with silica, the temperature is relatively less prominent, and the silane coupling agent is very dependent on temperature and time, so when the silica is used in tire industrial applications, It is usually processed by temperature mixing above 150 degrees. On the contrary, in the shoe industry, silane coupling is not suitable for the high temperature treatment of white carbon black, because in the shoe industry, most of them are small and medium-sized rubber enterprises, generally using low-speed internal mixers or open mills, and a few The company uses a high speed internal mixer. However, most of the products are light-colored, transparent and colored products. Even if the embryos are mixed on a high-speed internal mixer, it is necessary to add sulfur or add or add color to the open mill, and use a silane coupling agent. Although the high-temperature modified white carbon black has been improved in physical properties, at the same time, the adhesion of silane to metal is enhanced, and the sticky roller often occurs during the filming operation, which seriously affects the filming process, and at the same time, the handicraft industry For the main molded products, there are always certain variables in the vulcanization temperature and time, and the vulcanization time is generally a few minutes of rapid system, so the vulcanization flat period of the rubber must be good. The use of sulfur-modified silane coupling agent-modified silica to make the vulcanization process of the formulation more complicated, so that surfactant modification or a small amount of a silane coupling agent is generally used in the shoe industry.
Modification with a silane coupling agent is also a commonly used method in silica composites. The molecular structure is X3-Si-R. X is a hydrolyzable siloxane group, and after hydrolysis, a silanol group is formed to condense with a hydroxyl group on the surface of the filler to form a chemical bond. R is an organic functional group, which tends to produce chemical bonding during vulcanization of the rubber. The silane coupling agent is multi-layered on the surface of the filler, so the surface modification effect of the silane coupling agent on the white carbon black is much higher than that of the active agent. Surface treatment. Which silane is selected as the surface modification agent for silica, depending on the vulcanization system of the rubber, because different functional groups have different reaction abilities to rubber molecules. Generally, mercapto silane coupling agents are suitable for sulfur vulcanization systems, ethylene. The base or methacryl silane coupling agent is suitable for peroxide curing systems, and the amine and epoxy silanes are suitable for urethane rubber. The surface-modified white carbon black not only reduces the viscosity of the rubber compound, but also stabilizes the rubber compound and prevents the structuring process of the rubber compound. The silica-based disulfide-based white carbon black compound is modified with silane Si69 and has been widely used in the rubber industry.
Tetrasulfide Si69 is a sulfur-bearing compound. The Si69 modified silica gel is used in rubber products to make the vulcanization reaction of vulcanizate more complicated. Si69 is also a vulcanizing agent. It can be monosulfide. Or the form of polysulfide bond participates in the vulcanization reaction of rubber, which increases the crosslink density of vulcanizate. Generally, the vulcanization rate of Si69 is slightly slower than the vulcanization rate of sulfur, so it has certain anti-reverse property when vulcanizing natural rubber. The balance vulcanization system is designed by using this feature, so the amount of Si69 must be properly controlled, otherwise it will affect the physical properties of the rubber compound.
When a small amount of silane coupling agent is mixed at a temperature of 120 degrees or less, it is difficult to achieve an optimum reaction amount, but when used together with an active agent, good effects can be obtained, and the reaction mechanism is more complicated.
Practice has proved that whether it is a light-colored rubber compound formula of silica alone or a black rubber compound with carbon black, the addition of the corresponding amine or polyol surfactant for surface treatment is the most basic process, when the physical and mechanical properties cannot be satisfied. When required, surface modification with a silane coupling agent is one of the most commonly used methods in the footwear industry.