Most of the compression rubber for ordinary V-belts in foreign countries is SBR/natural rubber body and some chloroprene rubber. Transmission belt is a dynamic use of rubber products, the formula should take into account the dynamic cranking performance, heat generation, cover rubber should also be considered abrasion resistance, the rubber content should not be too low. High-grade drive belts such as narrow V-belts, agricultural V-belts, V-belts with cut edges, multiribbed belts and synchronous belts are widely used in chloroprene rubber. chloroprene rubber has high strength, heat resistance, aging resistance, ozone resistance, abrasion resistance, good flexural fatigue, and good adhesion with other materials. The applicable temperature range is generally -30~100℃. Most foreign transmission belts use low crystallinity general-purpose chloroprene rubber. The following are the performance indexes of the two grades of neoprene used in this study
CR232: This product is a chloroprene polymer with diisopropyl dithiocarbonate as the regulator. The crystallization speed is medium, the density is 1.23, beige lumps, non-polluting. It has good heat resistance and high temperature stability. It can be used for all kinds of light-colored rubber products, such as seals, dust cover, rollers, lining, hose outer sheath and other rubber miscellaneous parts. This product is similar to DuPont's W-type and Nidec's M-40-type chloroprene rubber.
CR322: This product is a chloroprene polymer with sulfur and diisopropyl dithiocarbonate as the mixing and adjusting agent. Medium crystallization speed, density 1.23, beige or brown lumps, non-polluting. High tear strength, processing performance is better than sulfur-regulated rubber. It can be used in the manufacture of cable sheaths, conveyor belts and other rubber products. This product is similar to DuPont GW type rubber.
2.1 Influence of different grades and dosage of CR on the vulcanization performance and Mooney viscosity of V-belt compression rubber.
With the increase of CR2322 dosage, t 10, t 90 first shorten and then lengthen, this is because CR2322 is non-sulfur-conditioned, ZnO, MgO as CR2322 sulfurizing agent dosage fixed, CR2322 dosage is equivalent to the relative sulfurizing agent of each CR is less, so the greater the dosage of CR2322 t 10, t 90 longer. And M H-M L does not change much. In addition, as the amount of CR3222 increases, t 10 and t 90 are shorter. This is due to the fact that CR3222 is a mixed and adjusted type, ZnO, MgO and S work together as vulcanizing agents, and because CR itself has shorter and faster coking time than NR/BR, the vulcanization speed becomes faster with the increase in the dosage of CR3222, and the M H-M L is gradually increased. Finally, under the current vulcanization system, CR3222 has shorter burning time, faster vulcanization rate and higher degree of vulcanization than CR2322.
The viscosity of mooney increased significantly with the increase of CR dosage. CR2322 increases more than CR3222 with increasing CR dosage, but CR3222 is larger when the same amount of CR is used.
2.2 The effect of different grades and dosage of CR on the physical and mechanical properties of V-belt compression rubber
With the increase of CR2322 dosage, the overall change of tensile strength is not significant, the elongation at break decreases, the 100% tensile stress and hardness increase. And at 100 ℃ with the aging time extension, tensile strength, tearing elongation decreased and the more CR2322 dosage, tensile strength, tearing elongation decreased less; with the aging time extension of 100% constant elongation, hardness increased, and different dosage of CR2322, 100% constant elongation, hardness increased by a small margin, but are smaller than the formula without CR2322.
With the increase of CR3222 dosage when not aged, the tensile strength did not change much, the tensile elongation decreased, the 100% constant tensile stress decreased first and then increased, and the hardness did not change much. And at 100 ℃ environment with the aging time extension, tensile strength, tearing elongation decreased and different dosage of CR3222 tensile strength, tearing elongation decreased by a small amount, but are smaller than the formula without CR3222; with the aging time extension of the 100% fixed tensile, hardness are increased, and different dosage of CR3222 of the 100% fixed tensile, hardness increase is not much different. Under different aging time of the same amount of CR at 100 ℃, the change rate of tensile strength of CR3222 is smaller than that of CR2322 with the aging time prolonged; the change rate of tearing elongation, 100% elongation, and Shore A hardness of CR3222 and CR2322 are not very much different from those of CR2322.
Under the current sulfide system, the flexural property of CR2322 is much better than that of CR3222 at 80 ℃, and as the amount of CR2322 increases, the best flexural property is achieved when the amount of CR2322 is 20 portions, and the flexural property deteriorates as the amount of CR3222 increases.
2.3 Mullins Effect of Different Grades and Dosages of CR on V-belt Compression Adhesives
Since the compression rubber is subjected to repetitive compression stress during normal use, and the Mullins effect under compression characterizes the stress softening of vulcanized rubber under repetitive compression, the compression rubber needs to have good stiffness under cyclic compression stress, and the stress softening should be as small as possible, so the Mullins effect under compression is used to characterize the state of compression rubber's stress softening. The normal temperature of ordinary V-belts is about 80 ℃, so in order to simulate the normal use of the compression adhesive, the Mullins effect at 80 ℃ was tested to reflect the real use of the state.
With the increase of the amount of CR2322, the maximum compression force increases before and after 100℃×24h aging. When the number of CR2322 used is the same, the maximum compression force increases significantly after 100 ℃ × 24 h aging. Since the smaller difference between the first and third compression forces indicates that the Mullins effect is weaker, the Mullins effect is obviously weakened with the increase in the amount of CR2322, and the Mullins effect is still weakened with the increase in the amount of CR2322 after aging at 100 ℃ × 24 h. However, compared with that before aging, the maximum compression force value increases before and after aging. However, compared with that before aging, the degree of Mullins effect increased after 100 ℃ × 24 h aging, and the degree of Mullins effect increased decreased with the increase of CR2322 dosage.
CR3222 has a similar pattern with CR2322 in terms of Mullins effect. A longitudinal comparison between CR3222 and CR2322 shows that in terms of maximum force, CR3222 is significantly larger than CR2322 at the same CR dosage, and the same is true after aging at 100 ℃ × 24 h. In terms of the Mullins effect, the difference in the Mullins effect between CR3222 and CR2322 at the same CR dosage before aging at 100 ℃ × 24 h is not great, but the difference in the Mullins effect between CR2322 and CR322 at 100 ℃ × 24 h is not great. However, after aging at 100 ℃ × 24 h, the Mullins effect of CR3222 is weaker than that of CR2322 at the same CR dosage.
2.4 Effect of different grades and amounts of CR on the dynamic heat generation of V-belt compression rubber
The loss factor (tanδ), which is the tangent of the phase difference angle between the strain and stress cycle of a viscoelastic material under the action of an alternating force field, is also equal to the ratio of the loss modulus to the energy storage modulus of the material, and it is an important index for measuring the dynamic heat generation of rubber products. Therefore, the effects of different grades and amounts of CR on the tanδ of V-belt compression rubber were investigated.
The higher the test temperature, the lower the tanδ of the vulcanized rubber, and the higher the tanδ of the vulcanized rubber with the use of CR, this is related to the fact that CR has a Cl side group in its molecular structure.
This is related to the Cl side group in the molecular structure of CR. The tanδ of the vulcanized rubber decreases with increasing the amount of CR2322, but the difference is not obvious when the temperature is lower than 100℃. In addition, the tanδ of the vulcanized rubber decreases with increasing the amount of CR3222, but the difference is not obvious at less than 100°C. Moreover, the tanδ of the vulcanized rubber is the smallest at 20 parts of CR3222. In the longitudinal comparison, the tanδ of CR3222 is lower than that of CR2322 at the same temperature and the same amount of CR, which may be due to the difference in tanδ of the curing rubber due to the difference in molecular structure and the required vulcanization system on one hand, and due to the difference in tanδ of the curing rubber due to the difference in cross-linking density on the other hand.
3 Conclusion
(1) As the use of CR2322 increased, t 10 and t 90 were shortened and then lengthened, and M H-M L did not change much. With the increase of CR3222, t 10 and t 90 were shortened and M H-M L increased gradually. The viscosity of mooney increases significantly with the increase of CR dosage, and CR2322 is larger than CR3222 in terms of increasing amplitude, but the value of CR3222 is larger when the same amount of CR is used.
(2) With the increase in the use of CR2322, the overall tensile strength does not change much, the tensile strength decreases, the 100% elongation and hardness increase. With the increase of CR3222, the tensile strength does not change much, the elongation at tear decreases, the 100% elongation stress decreases and then increases, and the hardness does not change much. The retention rate of physical and mechanical properties of both CRs increased after aging at 100℃ × 24 h. The current vulcanization system was also found to have a high retention rate of physical and mechanical properties. Under the current vulcanization system, the flexural resistance of CR2322 is much better than that of CR3222 at 80℃.
(3) As the amount of CR is increased, the Mullins effect decreases and the maximum force increases. In terms of maximum force, CR3222 is obviously larger than CR2322 at the same CR dosage, and it is also the same after aging at 100 ℃ × 24 h. In terms of Mullins effect, before aging at 100 ℃ × 24 h, there is not much difference between CR3222 and CR2322 in terms of Mullins effect at the same CR dosage, but after aging at 100 ℃ × 24 h, CR3222 and CR2322 have much better flexural properties than CR2322 at the same CR dosage. However, after aging at 100 ℃ × 24 h, the Mullins effect of CR3222 is weaker than that of CR2322 at the same CR dosage.
(4) The tanδ of the vulcanized rubber decreases with the higher CR2322 usage, but the difference is not obvious when it is less than 100 ℃. In addition, as the amount of CR3222 increases, the tanδ of vulcanized rubber is the smallest when the amount of CR3222 is 20 parts. The tanδ of CR3222 is lower than that of CR2322 at the same test temperature and the same CR dosage.
