When it comes to zinc oxide, it can be said that there is no one in the rubber products industry. It can be used as an activator and accelerator in the production of rubber products. It can also be used as a reinforcing agent and oxidant, especially with hard fat. The synergistic effect of acid is more used by many rubber products processing enterprises; zinc oxide is easily mixed in the rubber compound, and it can be "glow-heated" in different rubber products, but it has a fatal defect, which is in the rubber compound. Hard to disperse? What should I do?
The reason why zinc oxide is difficult to disperse in the rubber compound is directly related to the electric charge it carries. The so-called homophobic repelling, the negatively charged zinc oxide and the same negatively charged raw rubber repel each other, thus zinc oxide. It is difficult to disperse evenly in the rubber. The rubber product manufacturer can only improve the zinc oxide during the kneading process by surface treatment, granulation or masterbatch, and adjusting the rubber sequence. Dispersibility.
1. Surface treatment: Zinc oxide is treated with surface active materials. Compared with untreated zinc oxide, the surface treated zinc oxide has better dispersibility in the rubber compound, and the debinding temperature is low and the input work is small during mixing. As a low-grade short-chain saturated fatty acid, propionic acid is a commonly used surface treatment agent for zinc oxide.
2. Granulation: ordinary zinc oxide can not be gathered in the short end of the top plug at a low time, resulting in zinc oxide not uniformly dispersed in the rubber; the essence of zinc oxide granulation is transmitted by the pressure roller through the pressure of the cylinder Zinc oxide, the compacted flake zinc oxide is automatically grooved into the crusher, broken into particles of uneven size and then into the granulator for dressing. The granulated zinc oxide is always at the bottom end of the upper plug when rubber is kneaded, and can be quickly dispersed in the rubber. It should be noted that the surface treated zinc oxide can also be granulated. When the granulated zinc oxide is kneaded, the mixing time is longer than ordinary zinc oxide due to low rotation speed, low pressure and difficulty in pulverization.
3. Making the masterbatch: The masterbatch is a mixture of the compounding agent in the production formula into a rubber compound, which is used as the base rubber for the next step. For ordinary zinc oxide, 70 parts by mass of zinc oxide and 30 parts by mass of the rubber compound can be made into the masterbatch, and the dispersion effect of zinc oxide in the rubber compound can be obviously improved by adding several times during the kneading, basically not Zinc oxide may be poorly dispersed in the rubber.
4. Adjust the feeding sequence: Zinc oxide is a typical alkaline substance. If it is added together with the acidic compounding agent, it will agglomerate and it will be difficult to disperse evenly in the rubber compound. Adding zinc oxide in the initial stage of mixing is beneficial to zinc oxide in the rubber compound. The dispersion in the middle, but at the same time will shorten the scorch time, so different rubber products need to be tested to find the best time to add zinc oxide; it is worth mentioning that zinc oxide and stearic acid have been used together in the rubber compound. Although the zinc salt formed in the middle can protect the weak bond in the rubber molecule by chelation, promote the formation of new crosslinks and increase the crosslink density of the rubber, but the same zinc salt agglomeration will also affect the zinc oxide. The dispersibility in the rubber compound, so the two need to be separately input, stearic acid is added to form stearic acid orientation alignment, and when zinc oxide is added, the affinity of the crosslinking to zinc oxide can be improved, thereby improving the mixing effect.
In order to improve the dispersibility of zinc oxide in rubber, there are still many problems that need to be paid attention to when processing rubber products. Do you have any good suggestions?