Differential scanning calorimeter for testing the degree of vulcanization of rubber

In the rubber production process, the degree of vulcanization directly affects the mechanical properties, heat resistance, and service life of the product. The traditional vulcanization testing method has problems such as long time consumption and low accuracy, while DSC technology can quickly and accurately evaluate the degree of vulcanization by monitoring the changes in thermal effects during the vulcanization process, providing scientific basis for optimizing production processes.

1、 Basic principle of DSC testing for rubber vulcanization

Vulcanization is the ultimate production process of rubber products, and the degree of vulcanization of rubber plays a critical role in product performance. In order to maximize the production capacity and product quality of the product, the vulcanization cycle is adjusted by optimizing the positive vulcanization point to obtain high-quality products. Various methods have been developed for testing the degree of vulcanization for a long time, such as tensile strength, modulus, elongation, hardness, permanent deformation, Mooney burn, stress relaxation, and other testing methods. This type of mechanical performance testing usually requires a long time and sometimes a large number of approximations. Differential scanning calorimeter is a precision instrument that can accurately measure the transition temperature and enthalpy, and is a thermal technology used to detect the characteristics of the heat absorption and release processes of elastic materials. Using DSC to conduct time temperature tests on uncured rubber materials, relevant crosslinking reaction heat curves (△ H, enthalpy) were obtained. It was found that as the degree of vulcanization increased, △ H decreased, and the rubber material tended to zero when it reached positive vulcanization, even exhibiting endothermic phenomena.

2、 Operation steps of the experiment

1. Experimental instrument: DZ-DSC400 differential scanning calorimeter

2. Experimental samples: Sample preparation should pay attention to representativeness and uniformity. Usually, rubber samples from different stages of vulcanization are taken, cut into thin slices of about 5-10mg, and placed in an aluminum crucible.

3. Experimental parameter settings: The heating rate is usually selected as 10 ℃/min, and the temperature range is determined according to the type of rubber, generally from room temperature to 250 ℃. In terms of atmosphere control, nitrogen protection is usually used to avoid oxidation effects, with a flow rate of 50-100ml/min.

4. Measurement chart:

Sample after vulcanization

Unsulfided samples

5. Graph analysis:

The rubber vulcanization process exhibits distinct characteristics on the DSC curve. In the initial stage, due to the cross-linking of rubber molecular chains, a clear exothermic peak will appear. As the sulfurization reaction proceeds, the exothermic peak gradually increases and then gradually decreases until the reaction is complete. Different types of rubber have different vulcanization heat characteristics. For example, the exothermic peak of natural rubber vulcanization usually occurs between 140-160 ℃, while the exothermic peak of styrene butadiene rubber is in the range of 150-170 ℃. By analyzing the position, shape, and area of the exothermic peak, the rate and degree of rubber vulcanization reaction can be determined.

3、 Application of DSC technology in the rubber industry

The application of DSC testing technology in the rubber industry has significant value. Firstly, it can significantly shorten the vulcanization testing time, from several hours in traditional methods to several tens of minutes, greatly improving production efficiency. Secondly, the testing accuracy is high, and it can detect small changes in the degree of vulcanization, which helps to control the stability of product quality.

In terms of process optimization, DSC technology can help determine the optimal parameters such as vulcanization temperature, time, and pressure. By systematically studying the changes in DSC curves under different process conditions, a relationship model between vulcanization process parameters and product performance can be established to achieve accurate regulation.

For the development of new materials, DSC technology can quickly evaluate the vulcanization characteristics of different formulations of rubber, accelerating the process of new product research and development. Meanwhile, in the quality control process, DSC testing can serve as a rapid detection method to promptly identify quality issues in the production process.

4、 Experimental conclusion

DSC technology provides an efficient and accurate method for testing the degree of rubber vulcanization, which not only improves product quality and production efficiency, but also provides strong support for process optimization and new material development. With the continuous improvement of product performance requirements in the rubber industry, the application prospects of DSC technology will be even broader.