Zinc oxide is mainly used as a vulcanizing active agent in rubber products, which can accelerate the speed of vulcanization and improve the degree of vulcanization, and is an integral part of the vulcanization system in rubber formulations. Compared with ordinary zinc oxide, ultrafine active zinc oxide has small particle size, large specific surface area, certain activity on the surface, permeability, good dispersion and other physicochemical properties. Therefore, replacing ordinary zinc oxide in rubber formulations can reduce its dosage without affecting the vulcanization characteristics of the rubber and the physical and mechanical properties of the vulcanized rubber.
Laboratory experiments
When the dosage of active zinc oxide was increased from 50% to 90%, the vulcanization induction time (t10) and positive vulcanization time (t90) of the rubber increased with the dosage of active zinc oxide.
The time of vulcanization induction period (t10) and positive vulcanization time (t90) were prolonged with the increase of the dosage, and the elongation and tensile properties of the rubber increased with the increase of the dosage of active zinc oxide, and the best performance was achieved when the dosage reached 70%. The hardness of the rubber material does not change much with the increase of active zinc oxide dosage.
Batch validation
When the dosage of active zinc oxide is 70% of ordinary zinc oxide, the physical and mechanical properties of the rubber material are comparable with those of ordinary zinc oxide. Selected the ratio, using a dense refiner, to carry out a large fit comparison test, the results are shown in Table 3. The test results show that the dosage of active zinc oxide
is 70% of the ordinary zinc oxide rubber tensile strength is higher than ordinary zinc oxide rubber, the rest of the performance indicators are close to the heat aging performance of the former is better than the latter.
Mixing
Ultrafine active zinc oxide is easy to fly when mixing due to small particle size and light weight. Mixing with the refiner can take the reverse order of mixing method, the first active zinc oxide into the refining chamber, and then cast other materials for the operation
Extrusion
The t10 of active zinc oxide is longer than that of ordinary zinc oxide, which is beneficial to the extrusion of the hose and reduces the problem of scorching due to the rise in temperature during extrusion. Practical production has proved that the rubber formulation using active zinc oxide, extrusion process performance is good. Extrusion
Machine temperature control: head temperature 70 ± 5 ℃, body temperature 50 ± 5 ℃, screw temperature 40 ± 5 ℃.
Vulcanization
The use of active zinc oxide t90 and ordinary zinc oxide is almost equivalent to the vulcanization temperature and time can be used in the original process.
Cost
The price of active zinc oxide is higher than ordinary zinc oxide, but the dosage can be reduced, according to the test, the hose formula can be used 70% of the dosage. The comprehensive cost will be lower.
Conclusion
(1) In the hose formula can be used 70% of the active zinc oxide instead of ordinary zinc oxide, the physical and mechanical properties of the vulcanized rubber basically remain unchanged or improved.
(2) Ultrafine active zinc oxide is used in hose, the operation process is normal. Because of the long t10 time, anti-scorch performance is good, conducive to extrusion.
(3) The use of ultrafine active zinc oxide can reduce the cost of rubber.
