Is there a relationship between the vulcanization temperature of rubber specimens and their elongation?

Cross-linking of sulfur occurs during the vulcanization process, which refers to the attachment of one or more sulfur atoms to the polymer chains to form bridge-like structures. As a result of the reaction, an elastomer is formed, whose properties have changed in many aspects; the vulcanizing agent can be sulfur or other related substances. 　　“The term “vulcanization” has a historical origin, as the first natural rubber products were cross-linked using sulfur as a cross-linking agent; with the development of the rubber industry, various non-sulfur cross-linking agents can now be used for this purpose. Therefore, the more scientific meaning of vulcanization should be “cross-linking” or “bridging”, that is, the process by which linear polymers form networked polymers through cross-linking. Cross-linking of sulfur occurs during the vulcanization process, which refers to the attachment of one or more sulfur atoms to the polymer chains to form bridge-like structures. As a result of the reaction, an elastomer is formed, whose properties have changed in many aspects; the vulcanizing agent can be sulfur or other related substances. In terms of physical properties, it is the process by which plastic rubber is transformed into elastic rubber or rigid rubber. “The meaning of “vulcanization” includes not only the actual cross-linking process but also the methods used to achieve cross-linking. 　　The vulcanization process can be divided into four stages, each with its own characteristics. By measuring the stress at a constant strain of the rubber compound (or using a vulcanization tester), it can be seen that the entire vulcanization process consists of four stages: vulcanization induction, pre-vulcanization, true vulcanization, and over-vulcanization (which, in the case of natural rubber, refers to the reversal of vulcanization). 　　During the sulfurization induction period (scorch time), cross-linking has not yet begun, and the rubber compound possesses good fluidity. This stage determines the scorching tendency of the compound and its processing safety. At the end of this stage, the rubber compound begins to cross-link and loses its fluidity. The length of the vulcanization induction period is related not only to the properties of the raw rubber itself but mainly depends on the additives used; for example, the use of retarder-type accelerators can result in a longer scorch time and greater processing safety. 　　After the sulfurization induction period comes the presulfurization stage, during which cross-linking occurs at a constant rate. During the pre-vulcanization stage, the degree of cross-linking is low; as a result, even at the later stages of vulcanization, the tensile strength and elasticity of the rubber do not reach the desired levels. However, its performance in terms of tear resistance and resistance to dynamic cracking is better than that of rubber vulcanized under normal conditions. 　　Upon reaching the full vulcanization stage, the various physical properties of the vulcanized rubber reach or come close to their optimal values, or achieve a comprehensive balance in terms of performance. 　　After the normal vulcanization stage (the vulcanization plateau), the over-vulcanization stage follows, which presents two scenarios: natural rubber exhibits a \"reversion\" phenomenon (a decrease in modulus at fixed strain), while the modulus at fixed strain of most synthetic rubbers (except butyl rubber) continues to increase. 　　For any rubber, vulcanization not only results in cross-linking, but also causes the breaking of cross-link chains and molecular chains due to the effects of heat and other factors. This phenomenon persists throughout the vulcanization process. During the oversulfurization stage, if cross-linking remains dominant, the rubber becomes hard and its tensile strength continues to increase; conversely, the rubber softens, that is, it returns to its original state. 　　The vulcanization process is primarily used to improve the properties of rubber products. Before vulcanization, there are no cross-links between the rubber molecules; as a result, they lack good physical and mechanical properties and have limited practical value. When a vulcanizing agent is added to rubber, heat treatment or other methods can cause cross-linking between the rubber molecules, resulting in the formation of a three-dimensional network structure. This improves the properties of the rubber; in particular, various physical and mechanical properties such as its stress at fixed elongation, elasticity, hardness, and tensile strength all increase. 　　Injection vulcanization: The most obvious difference between conventional molding and injection molding is that in the former, the rubber compound is filled into the mold cavity in a cold state, whereas in the latter, the rubber compound is heated and mixed before being injected into the mold cavity at a temperature close to the vulcanization temperature. Therefore, during the injection process, the heat provided by the heating template is used solely to maintain vulcanization; it can quickly heat the rubber compound to 190°C–220°C. During the molding process, the heat provided by the heated template is first used to preheat the rubber compound. Due to the poor thermal conductivity of rubber, if the product is thick, it takes a long time for heat to reach the center of the product. Using high-temperature vulcanization can also reduce the processing time to some extent, but it often causes charring at the edges of the products near the heat plate. 　　Using the injection vulcanization method can shorten the molding cycle and enable automated operation, which is most advantageous for mass production. Injection molding also has the following advantages: it eliminates processes such as preparing semi-finished products, demolding, and trimming the finished products ； High-quality products with stable dimensions and excellent physical and mechanical properties can be produced ； Reduce vulcanization time, improve production efficiency, decrease the amount of rubber compound used, lower costs, reduce waste, and enhance the economic profitability of the enterprise. 　　When using the injection vulcanization molding process, the following points should be noted: 1. Use a reasonable screw speed and back pressure, and control the appropriate temperature of the injection machine. Generally, it is advisable to keep the temperature at the discharge port moderate and control the temperature difference in the cycle to be no more than 30 degrees. 　　The purpose of the injection molding machine screw is to prepare an adequate amount of plastic material for each cycle at a selected and uniform temperature ； It clearly affects the production capacity of the injection molding machine. 　　Back pressure is generated by reducing the flow rate at the oil outlet in the injection cylinder, and it limits the pushing force exerted by the injection cylinder on the plastic material being injected. In practice, back pressure only slightly increases the shear on the rubber compound, without causing a decrease in the physical properties of the vulcanized product. 　　2. Nozzle design. The nozzle connects the injection nozzle to the mold, and it also plays a role in maintaining thermal balance. The pressure loss across the nozzle is converted into heat through injection. The rubber compound must under no circumstances be vulcanized at this location. Therefore, choosing the appropriate nozzle diameter is very important, as it affects the frictional heat generation at the nozzle, the pressure required for injecting the rubber compound, and the molding time. 　　3. Appropriate mold temperature, optimal vulcanization conditions. After selecting the optimal compound for the rubber mixture, it is important to coordinate the injection molding conditions with the vulcanization conditions. Compared to compression molding, in injection molding, due to the different temperature distributions on and within the mold surface, precise temperature control is necessary to achieve proper vulcanization, so that both the surface and the interior of the mold are under optimal vulcanization conditions. High temperatures increase the shrinkage rate of rubber, but the relationship between them is linear; a proper estimation should be made prior to production. Furthermore, in terms of molding pressure, high-pressure molding is highly advantageous, as pressure is inversely proportional to shrinkage. 　　4. Safe and reasonable rubber compound formulation design. For rubber compounds used in injection vulcanization molding, the following properties are required: (1) The Mooney scorch time of the rubber compound should be as long as possible to ensure maximum safety. Generally, the Menni scorch time should be twice as long as the residence time of the compound in the barrel. (2) Fast vulcanization speed: By making a reasonable choice of vulcanization systems for different rubber compounds and adding appropriate accelerators, the rubber compounds can achieve satisfactory efficiency during injection vulcanization. (3) It has good fluidity; this excellent flow property reduces the residence time of the compound, shortens the injection time, and enhances the resistance to scorching. 　　By selecting appropriate process conditions and a suitable rubber compound formula, and using the injection vulcanization process, the curing time can be 10 to 20 times faster than that of conventional compression vulcanization. Reduce compound loss by 10%~15%. 　　Nitrogen vulcanization process The main advantages of using nitrogen for vulcanization are energy savings and an extended lifespan for the capsules; it is possible to save 80% on steam usage, and the service life of the capsules can be doubled. Tires consume a large amount of heat and electricity during the vulcanization process; therefore, it is of great significance to develop and promote energy-saving vulcanization techniques. Due to its low molecular weight and small heat capacity, nitrogen does not absorb heat when filled into the interior of tire bladders, which prevents a drop in temperature; it also makes it less likely for the bladders to oxidize and break down. 　　The process characteristic of nitrogen vulcanization is that high-temperature and high-pressure steam is introduced first; after a few minutes, nitrogen is fed in, and vulcanization is completed using the \"constant pressure with variable temperature\" technique associated with nitrogen filling. Since the heat from several minutes of steam application is sufficient to vulcanize a tire, in theory it is enough as long as the temperature does not drop below 150°C before vulcanization is completed. However, when using nitrogen for vulcanization, high-temperature and high-pressure steam is introduced first, which creates a temperature difference between the upper and lower sides of the tire. To eliminate this temperature difference during vulcanization, it is necessary to arrange the injection points of the vulcanization medium properly and improve the sealing and thermal piping systems. 　　The purity of nitrogen used for vulcanization should be 99.99%, and ideally 99.999%. It is recommended that companies establish their own nitrogen production systems in order to reduce costs. Insufficient nitrogen purity can affect the lifespan of the capsules. 　　By applying the \"constant pressure and variable temperature\" vulcanization principle based on nitrogen sulfidation to the modification of the conventional cyclic superheated water vulcanization process, a new vulcanization process that uses high-temperature and high-pressure steam along with superheated water has been developed as a replacement for the traditional cyclic superheated water vulcanization process. During vulcanization, high-temperature and high-pressure steam is first introduced; after a few minutes, circulating superheated water is fed in, and after another few minutes, the return valve is closed to stop the circulation, until vulcanization is completed using the latent heat. According to theoretical calculations, using this new heating vulcanization method, its energy consumption is only 1/2 of that of the traditional vulcanization process. The above contains some general knowledge. But to answer the original poster’s question, it depends on what type of rubber it is in order to determine the specific effects. This post was last edited by zhouchu2001 on 2009-3-26 17:03.]

There is definitely a connection, but factors such as vulcanization time also need to be considered. Increasing the vulcanization temperature alone results in a decrease in elongation.

Vulcanization time, vulcanization pressure, and vulcanization temperature are the three key factors in the vulcanization process; changing any one of them will definitely have an impact.

With the same formula and the same processing process, the relationship between the vulcanization time of the test pieces and their elongation rate is such that, when the optimal vulcanization point is reached, the growth rate attains an ideal value. If there is an excess of sulfur, the elongation rate generally decreases. If there is a deficiency of sulfur, the elongation rate may increase. Of course, in cases of severe sulfur deficiency, the elongation rate will definitely be low, as the necessary level of cross-linking is not achieved, and the material does not possess sufficient rubber-like properties.